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Publications of year 2012

Articles in journal or book chapters

  1. Esteban Aguilera, Matteo Nannini, and Andreas Reigber. Multisignal Compressed Sensing for Polarimetric SAR Tomography. IEEE Geosci. Remote Sens. Lett., 5(9):871-875, September 2012. Keyword(s): SAR Processing, SAR Tomography, Tomography, Compressed sensing, Remote sensing, Sensors, Tomography, Vectors, compressed sensing, compressive sensing, CS, geometry, image reconstruction, image sensors, radar imaging, radar polarimetry, synthetic aperture radar, tomography, 3D imaging, DCS, E-SAR sensor, German Aerospace Center, azimuth-range pixel, data collection processing, distributed compressed sensing, multisignal compressed sensing, parallel track, polarimetric L-band data, polarimetric SAR sensor, polarimetric SAR tomography, polarimetric channel, polarimetric synthetic aperture radar sensor, repeat-pass acquisition geometry, signal reconstruction, temporal baseline, tomographic signal, vertical reflectivity function, Compressed sensing (CS), distributed compressed sensing (DCS), polarimetry, synthetic aperture radar (SAR) tomography, L-band, E-SAR, F-SAR.
    Abstract: In recent years, 3-D imaging by means of polarimetric synthetic aperture radar (SAR) sensors has become a field of intensive research. In SAR tomography, the vertical reflectivity function for every azimuth /range pixel is usually recovered by processing data collected using a defined repeat-pass acquisition geometry. The most common approach is to generate a synthetic aperture in the elevation direction through imaging from a large number of parallel tracks. This imaging technique is appealing, since it is very simple. However, it has the drawback that large temporal baselines can severely affect the reconstruction. In an attempt to reduce the number of parallel tracks, we propose a new approach that exploits structural correlations between neighboring azimuth-range pixels and/or polarimetric channels. As a matter of fact, this can be done under the framework of distributed compressed sensing (CS) (DCS), which stems from CS theory, thus also exploiting sparsity in the tomographic signal. Finally, results demonstrating the potential of the DCS methodology will be validated by using fully polarimetric L-band data acquired by the E-SAR sensor of the German Aerospace Center (DLR).

    @Article{aguileraNanniniReigberGRSL2012,
    author = {Aguilera, Esteban and Nannini, Matteo and Reigber, Andreas},
    title = {Multisignal Compressed Sensing for Polarimetric {SAR} Tomography},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2012},
    volume = {5},
    number = {9},
    pages = {871-875},
    month = sep,
    issn = {1545-598X},
    abstract = {In recent years, 3-D imaging by means of polarimetric synthetic aperture radar (SAR) sensors has become a field of intensive research. In SAR tomography, the vertical reflectivity function for every azimuth /range pixel is usually recovered by processing data collected using a defined repeat-pass acquisition geometry. The most common approach is to generate a synthetic aperture in the elevation direction through imaging from a large number of parallel tracks. This imaging technique is appealing, since it is very simple. However, it has the drawback that large temporal baselines can severely affect the reconstruction. In an attempt to reduce the number of parallel tracks, we propose a new approach that exploits structural correlations between neighboring azimuth-range pixels and/or polarimetric channels. As a matter of fact, this can be done under the framework of distributed compressed sensing (CS) (DCS), which stems from CS theory, thus also exploiting sparsity in the tomographic signal. Finally, results demonstrating the potential of the DCS methodology will be validated by using fully polarimetric L-band data acquired by the E-SAR sensor of the German Aerospace Center (DLR).},
    doi = {10.1109/LGRS.2012.2185482},
    file = {:aguileraNanniniReigberGRSL2012.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Tomography,Compressed sensing;Remote sensing;Sensors;Tomography;Vectors;compressed sensing; compressive sensing, CS, geometry;image reconstruction;image sensors;radar imaging;radar polarimetry;synthetic aperture radar;tomography;3D imaging;DCS;E-SAR sensor;German Aerospace Center;azimuth-range pixel;data collection processing;distributed compressed sensing;multisignal compressed sensing;parallel track;polarimetric L-band data;polarimetric SAR sensor;polarimetric SAR tomography;polarimetric channel;polarimetric synthetic aperture radar sensor;repeat-pass acquisition geometry;signal reconstruction;temporal baseline;tomographic signal;vertical reflectivity function;Compressed sensing (CS);distributed compressed sensing (DCS);polarimetry;synthetic aperture radar (SAR) tomography; L-band, E-SAR, F-SAR},
    pdf = {../../../docs/aguileraNanniniReigberGRSL2012.pdf},
    
    }
    


  2. J. N. Ash. An Autofocus Method for Backprojection Imagery in Synthetic Aperture Radar. IEEE Geoscience and Remote Sensing Letters, 9(1):104-108, January 2012. Keyword(s): SAR Processing, Autofocus, autoregressive processes, convolution, digital elevation models, geophysical image processing, geophysical techniques, radar imaging, synthetic aperture radar, convolution backprojection, autofocus method, backprojection imagery, autofocus routine, spotlight-mode synthetic aperture radar data, image sharpness, imaging geometry, wide-angle aperture, digital elevation map, image-quality-based autofocus approach, natural geometric interpretation, optimal single-pulse phase correction, quartic polynomial, sequential imaging application, autoregressive backprojection, Synthetic aperture radar, Imaging, Apertures, Measurement, Optimization, History, Azimuth, Autofocus, autoregressive backprojection (ARBP), convolution BP (CBP) imaging, synthetic aperture radar (SAR).
    Abstract: In this letter, we present an autofocus routine for backprojection imagery from spotlight-mode synthetic aperture radar data. The approach is based on maximizing image sharpness and supports the flexible collection and imaging geometries of BP, including wide-angle apertures and the ability to image directly onto a digital elevation map. While image-quality-based autofocus approaches can be computationally intensive, in the backprojection setting, we demonstrate a natural geometric interpretation that allows for optimal single-pulse phase corrections to be derived in closed form as the solution of a quartic polynomial. The approach is applicable to focusing standard backprojection imagery, as well as providing incremental focusing in sequential imaging applications based on autoregressive backprojection. An example demonstrates the efficacy of the approach applied to real data for a wide-aperture backprojection image.

    @Article{ashGRSL2012AutofocusForBackprojectionImageryInSAR,
    author = {J. N. {Ash}},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    title = {An Autofocus Method for Backprojection Imagery in Synthetic Aperture Radar},
    year = {2012},
    issn = {1558-0571},
    month = {Jan},
    number = {1},
    pages = {104-108},
    volume = {9},
    abstract = {In this letter, we present an autofocus routine for backprojection imagery from spotlight-mode synthetic aperture radar data. The approach is based on maximizing image sharpness and supports the flexible collection and imaging geometries of BP, including wide-angle apertures and the ability to image directly onto a digital elevation map. While image-quality-based autofocus approaches can be computationally intensive, in the backprojection setting, we demonstrate a natural geometric interpretation that allows for optimal single-pulse phase corrections to be derived in closed form as the solution of a quartic polynomial. The approach is applicable to focusing standard backprojection imagery, as well as providing incremental focusing in sequential imaging applications based on autoregressive backprojection. An example demonstrates the efficacy of the approach applied to real data for a wide-aperture backprojection image.},
    doi = {10.1109/LGRS.2011.2161456},
    keywords = {SAR Processing, Autofocus, autoregressive processes;convolution;digital elevation models;geophysical image processing;geophysical techniques;radar imaging;synthetic aperture radar;convolution backprojection;autofocus method;backprojection imagery;autofocus routine;spotlight-mode synthetic aperture radar data;image sharpness;imaging geometry;wide-angle aperture;digital elevation map;image-quality-based autofocus approach;natural geometric interpretation;optimal single-pulse phase correction;quartic polynomial;sequential imaging application;autoregressive backprojection;Synthetic aperture radar;Imaging;Apertures;Measurement;Optimization;History;Azimuth;Autofocus;autoregressive backprojection (ARBP);convolution BP (CBP) imaging;synthetic aperture radar (SAR)},
    owner = {ofrey},
    
    }
    


  3. A. E. A. Blomberg, A. Austeng, and Roy E. Hansen. Adaptive Beamforming Applied to a Cylindrical Sonar Array Using an Interpolated Array Transformation. IEEE Journal of Oceanic Engineering, 37(1):25-34, January 2012. Keyword(s): Synthetic Aperture Sonar, SAS, array signal processing, interpolation, sonar arrays, sonar signal processing, SX90 fish finding sonar, adaptive beamforming, adaptive minimum variance, amplitude estimation, azimuth resolution, cylindrical sonar array, interference rejection, interpolated array transformation, phase estimation, virtual linear array, Array signal processing, Arrays, Covariance matrix, Signal resolution, Sonar applications, Vectors, Adaptive signal processing, array signal processing, beam steering, imaging, sonar, spatial resolution.
    Abstract: In applications such as fishery sonar and navigation, cylindrical or spherical arrays are often used because of the need for a 360� field of view. However, adaptive beamforming methods, known for their high angular resolution and interference rejection capabilities, often rely on a Vandermonde structure of the steering vectors. This is generally not the case for nonlinear arrays. In this paper, we use an interpolated array transformation to map the data to a virtual linear array before adaptive beamforming. We evaluate the performance of two different adaptive beam- formers using simulations as well as experimental data from the SX90 fish finding sonar. We show that the adaptive minimum variance (MV) and amplitude and phase estimation of a sinusoid (APES) beamformers offer a significant improvement in azimuth resolution compared to the conventional delay-and-sum (DAS) beamformer. The APES beamformer offers slightly more reliable amplitude estimates in the direction of interest compared to the MV beamformer, at the cost of a somewhat lower azimuth resolution. When applied to data from the SX90 fish finding sonar, the MV beamformer offers a 40%-50% improvement in resolution, while the APES beamformer offers an improvement of 20%-30%.

    @Article{blombergAustengHansenJOE2012AdaptiveBeamformingCylindricalSonarArray,
    author = {A. E. A. Blomberg and A. Austeng and Roy E. Hansen},
    title = {Adaptive Beamforming Applied to a Cylindrical Sonar Array Using an Interpolated Array Transformation},
    journal = {IEEE Journal of Oceanic Engineering},
    year = {2012},
    volume = {37},
    number = {1},
    pages = {25-34},
    month = jan,
    issn = {0364-9059},
    abstract = {In applications such as fishery sonar and navigation, cylindrical or spherical arrays are often used because of the need for a 360� field of view. However, adaptive beamforming methods, known for their high angular resolution and interference rejection capabilities, often rely on a Vandermonde structure of the steering vectors. This is generally not the case for nonlinear arrays. In this paper, we use an interpolated array transformation to map the data to a virtual linear array before adaptive beamforming. We evaluate the performance of two different adaptive beam- formers using simulations as well as experimental data from the SX90 fish finding sonar. We show that the adaptive minimum variance (MV) and amplitude and phase estimation of a sinusoid (APES) beamformers offer a significant improvement in azimuth resolution compared to the conventional delay-and-sum (DAS) beamformer. The APES beamformer offers slightly more reliable amplitude estimates in the direction of interest compared to the MV beamformer, at the cost of a somewhat lower azimuth resolution. When applied to data from the SX90 fish finding sonar, the MV beamformer offers a 40%-50% improvement in resolution, while the APES beamformer offers an improvement of 20%-30%.},
    doi = {10.1109/JOE.2011.2169611},
    file = {:blombergAustengHansenJOE2012AdaptiveBeamformingCylindricalSonarArray.pdf:PDF},
    keywords = {Synthetic Aperture Sonar, SAS,array signal processing;interpolation;sonar arrays;sonar signal processing;SX90 fish finding sonar;adaptive beamforming;adaptive minimum variance;amplitude estimation;azimuth resolution;cylindrical sonar array;interference rejection;interpolated array transformation;phase estimation;virtual linear array;Array signal processing;Arrays;Covariance matrix;Signal resolution;Sonar applications;Vectors;Adaptive signal processing;array signal processing;beam steering;imaging;sonar;spatial resolution},
    
    }
    


  4. Federica Bordoni, Marwan Younis, and Gerhard Krieger. Ambiguity Suppression by Azimuth Phase Coding in Multichannel SAR Systems. IEEE Trans. Geosci. Remote Sens., 50(2):617-629, February 2012. Keyword(s): SAR Processing, APC technique, ambiguity suppression, azimuth phase coding, digital beamforming, flexible SAR systems, multichannel SAR systems, multiple transmit-receive channels, numerical analysis, reflector antenna, spaceborne SAR systems, spaceborne synthetic aperture radar systems, array signal processing, numerical analysis, phase coding, radar signal processing, remote sensing by radar, synthetic aperture radar.
    Abstract: The current generation of spaceborne synthetic aperture radar (SAR) systems suffers from a tradeoff between the achievable spatial resolution and swath width. This has motivated intensive research both on more flexible SAR systems, using multiple transmit/receive channels, and on techniques for removing the ambiguities. Among these techniques, the azimuth phase coding (APC), recently proposed to suppress range ambiguities in conventional SAR systems, stands out for its negligible implementation complexity and its effectiveness for point and distributed ambiguities. This paper investigates the possibility of applying the APC technique to the new, forthcoming generation of multichannel SAR systems, based on digital beamforming on receive. The extension of APC to multichannel SAR systems is mathematically described. Specific merit figures are defined to quantify the APC performance. A numerical analysis is developed to characterize the influence on the APC behaviors of the main SAR system parameters. Finally, an example of APC performance is provided, by considering two multichannel SAR systems based on a planar and a reflector antenna.

    @Article{bordoniYounisKrieger2012,
    author = {Bordoni, Federica and Younis, Marwan and Krieger, Gerhard},
    title = {Ambiguity Suppression by Azimuth Phase Coding in Multichannel {SAR} Systems},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2012},
    volume = {50},
    number = {2},
    pages = {617-629},
    month = feb,
    issn = {0196-2892},
    abstract = {The current generation of spaceborne synthetic aperture radar (SAR) systems suffers from a tradeoff between the achievable spatial resolution and swath width. This has motivated intensive research both on more flexible SAR systems, using multiple transmit/receive channels, and on techniques for removing the ambiguities. Among these techniques, the azimuth phase coding (APC), recently proposed to suppress range ambiguities in conventional SAR systems, stands out for its negligible implementation complexity and its effectiveness for point and distributed ambiguities. This paper investigates the possibility of applying the APC technique to the new, forthcoming generation of multichannel SAR systems, based on digital beamforming on receive. The extension of APC to multichannel SAR systems is mathematically described. Specific merit figures are defined to quantify the APC performance. A numerical analysis is developed to characterize the influence on the APC behaviors of the main SAR system parameters. Finally, an example of APC performance is provided, by considering two multichannel SAR systems based on a planar and a reflector antenna.},
    doi = {10.1109/TGRS.2011.2161672},
    file = {:bordoniYounisKrieger2012.pdf:PDF},
    keywords = {SAR Processing, APC technique;ambiguity suppression;azimuth phase coding;digital beamforming;flexible SAR systems;multichannel SAR systems;multiple transmit-receive channels;numerical analysis;reflector antenna;spaceborne SAR systems;spaceborne synthetic aperture radar systems;array signal processing;numerical analysis;phase coding;radar signal processing;remote sensing by radar;synthetic aperture radar},
    owner = {ofrey},
    pdf = {../../../docs/bordoniYounisKrieger2012.pdf},
    
    }
    


  5. A. Budillon, A. Evangelista, and G. Schirinzi. GLRT Detection of Moving Targets via Multibaseline Along-Track Interferometric SAR Systems. IEEE Geosci. Remote Sens. Lett., 9(3):348-352, May 2012. Keyword(s): SAR Processing, SAR Tomography, Tomography, ATI, MTI, Along-track interferometry, Moving target indication, Multibaseline InSAR, InSAR, SAR Interferometry.
    Abstract: Along-track interferometric synthetic aperture radar systems can be used for ground moving target indication. We analyze a scheme for detecting moving targets with unknown parameters (velocity and signal-to-clutter ratio) and with constant false-alarm rates, based on the generalized likelihood ratio test (GLRT), and adopting a Gaussian model for target and clutter signals. We compare its performance with the one obtained in the ideal case of known target parameters applying the likelihood ratio test (LRT). A closed form for the LRT receiver operating characteristic is derived and used as reference for GLRT performance assessment. The analysis is carried out on simulated TerraSAR-X data.

    @Article{6058583,
    Title = {{GLRT} Detection of Moving Targets via Multibaseline Along-Track Interferometric {SAR} Systems},
    Author = {Budillon, A. and Evangelista, A. and Schirinzi, G.},
    Doi = {10.1109/LGRS.2011.2168381},
    ISSN = {1545-598X},
    Month = may,
    Number = {3},
    Pages = {348-352},
    Volume = {9},
    Year = {2012},
    Abstract = {Along-track interferometric synthetic aperture radar systems can be used for ground moving target indication. We analyze a scheme for detecting moving targets with unknown parameters (velocity and signal-to-clutter ratio) and with constant false-alarm rates, based on the generalized likelihood ratio test (GLRT), and adopting a Gaussian model for target and clutter signals. We compare its performance with the one obtained in the ideal case of known target parameters applying the likelihood ratio test (LRT). A closed form for the LRT receiver operating characteristic is derived and used as reference for GLRT performance assessment. The analysis is carried out on simulated TerraSAR-X data.},
    Journal = {IEEE Geosci. Remote Sens. Lett.},
    Keywords = {SAR Processing, SAR Tomography, Tomography, ATI, MTI, Along-track interferometry, Moving target indication, Multibaseline InSAR, InSAR, SAR Interferometry} 
    }
    


  6. Karlus A. Cmara de Macedo, Christian Wimmer, T.L.M. Barreto, Dieter Lubeck, J.R. Moreira, L.M.L. Rabaco, and W.J. de Oliveira. Long-Term Airborne DInSAR Measurements at X- and P-Bands: A Case Study on the Application of Surveying Geohazard Threats to Pipelines. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 5(3):990-1005, June 2012. Keyword(s): SAR Processing, Deformation measurements, displacement measurements, DInSAR, differential interferometry, Airborne SAR, X-band, P-Band, OrbiSAR, Orbisat, BRADAR, geohazards, hazards, motion measurement, pipelines, radar interferometry, remote sensing by radar, surveying, synthetic aperture radar, time series, Brazil, OrbiSAR system, OrbiSat, P-band airborne DInSAR, PROTRAN, Petrobras, Sao Sebastiao, X-band airborne DInSAR, airborne DInSAR data, geodynamic processes, geohazard risk monitoring, geohazard risks, land movement measurement, long term airborne DInSAR measurements, pipeline geohazard threat surveying, pipeline structural damage, residual motion errors, time series analysis, Antenna measurements, Antennas, Global Positioning System, Interferometry, Pipelines, Radar tracking, Synthetic aperture radar, Airborne, P-band, X-band, differential interferometry (DInSAR), geohazards.
    Abstract: Recently some experiments demonstrated that reliable DInSAR measurements can be achieved at any band and that further time-series analyses can be applied to airborne data. However, most of the airborne DInSAR results, including the time-series, published so far have focused on short-term analyses (baselines within hours or few days). This paper presents the first long-term airborne DInSAR survey at P- and X-band with temporal baselines of 1 year and 3 months. The survey was performed by the OrbiSAR system of OrbiSat under contract with Petrobras (PROTRAN), as part of a project to investigate the potential of DInSAR technique to identify, prior to structural damage, geohazards threats to the oil/gas pipelines in Sao Sebastiao-SP, Brazil. After 1 year and 3 months, the P-band data have interferometric coherence equal or greater than 0.3 for approximately 80% of the imaged dense vegetated areas. At X-band, we achieved coherence equal or greater than 0.3 in the urban area. After removing all residual motion errors with proper up-to-date processing, we derived, for the P-band data, land movements with absolute accuracy in the order of centimeters. For X-band we derived land movement measurements with absolute accuracy in the order of millimeters. Through field work evidences, the paper analyses the causes of these centimeter to millimeter land movements, and how they are related to geodynamic processes and geohazard risks. A comparison between the DInSAR and in-loco inclinometer measurements is presented. The paper suggests some possible operational scenarios and discusses on the potential of the airborne DInSAR for geohazard risk monitoring.

    @Article{deMacedoWimmerBarretoLubeckMoreiraRabacoOliveiraJSTARS2012AirborneDINSAR,
    author = {C\^amara de Macedo, Karlus A. and Wimmer, Christian and Barreto, T.L.M. and Lubeck, Dieter and Moreira, J.R. and Rabaco, L.M.L. and de Oliveira, W.J.},
    title = {Long-Term Airborne {DInSAR} Measurements at {X-} and {P-}Bands: A Case Study on the Application of Surveying Geohazard Threats to Pipelines},
    journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
    year = {2012},
    volume = {5},
    number = {3},
    pages = {990-1005},
    month = jun,
    issn = {1939-1404},
    abstract = {Recently some experiments demonstrated that reliable DInSAR measurements can be achieved at any band and that further time-series analyses can be applied to airborne data. However, most of the airborne DInSAR results, including the time-series, published so far have focused on short-term analyses (baselines within hours or few days). This paper presents the first long-term airborne DInSAR survey at P- and X-band with temporal baselines of 1 year and 3 months. The survey was performed by the OrbiSAR system of OrbiSat under contract with Petrobras (PROTRAN), as part of a project to investigate the potential of DInSAR technique to identify, prior to structural damage, geohazards threats to the oil/gas pipelines in Sao Sebastiao-SP, Brazil. After 1 year and 3 months, the P-band data have interferometric coherence equal or greater than 0.3 for approximately 80% of the imaged dense vegetated areas. At X-band, we achieved coherence equal or greater than 0.3 in the urban area. After removing all residual motion errors with proper up-to-date processing, we derived, for the P-band data, land movements with absolute accuracy in the order of centimeters. For X-band we derived land movement measurements with absolute accuracy in the order of millimeters. Through field work evidences, the paper analyses the causes of these centimeter to millimeter land movements, and how they are related to geodynamic processes and geohazard risks. A comparison between the DInSAR and in-loco inclinometer measurements is presented. The paper suggests some possible operational scenarios and discusses on the potential of the airborne DInSAR for geohazard risk monitoring.},
    doi = {10.1109/JSTARS.2012.2187275},
    file = {:deMacedoWimmerBarretoLubeckMoreiraRabacoOliveiraJSTARS2012AirborneDINSAR.pdf:PDF},
    keywords = {SAR Processing, Deformation measurements, displacement measurements, DInSAR, differential interferometry, Airborne SAR, X-band, P-Band, OrbiSAR, Orbisat, BRADAR, geohazards, hazards;motion measurement;pipelines;radar interferometry;remote sensing by radar; surveying;synthetic aperture radar;time series;Brazil;OrbiSAR system;OrbiSat;P-band airborne DInSAR; PROTRAN;Petrobras;Sao Sebastiao;X-band airborne DInSAR;airborne DInSAR data;geodynamic processes; geohazard risk monitoring;geohazard risks;land movement measurement; long term airborne DInSAR measurements;pipeline geohazard threat surveying; pipeline structural damage;residual motion errors;time series analysis; Antenna measurements;Antennas;Global Positioning System;Interferometry; Pipelines;Radar tracking;Synthetic aperture radar;Airborne;P-band;X-band; differential interferometry (DInSAR);geohazards;land movements;pipelines; repeat-pass;synthetic aperture radar (SAR)},
    pdf = {../../../docs/deMacedoWimmerBarretoLubeckMoreiraRabacoOliveiraJSTARS2012AirborneDINSAR.pdf},
    
    }
    


  7. A. Elsherbini and K. Sarabandi. Compact Directive Ultra-Wideband Rectangular Waveguide Based Antenna for Radar and Communication Applications. IEEE_J_AP, 60(5):2203-2209, May 2012. Keyword(s): UHF antennas, antenna feeds, baluns, microwave antennas, planar antennas, radar antennas, ultra wideband antennas, ultra wideband communication, ultra wideband radar, waveguide antennas, VSWR, aperture field distribution, balun structure, communication applications, compact directive ultra-wideband rectangular waveguide based antenna, cross-polarization performance, directive ultra-wideband antenna, fabrication tolerances, frequency 1.08 GHz to 4.9 GHz, integrated balun design, planar antenna aperture, polarizer, radar applications, rectangular waveguide antenna feeding structure, rectangular waveguide aperture antennas, standard balun, waveguide mode, Apertures, Directive antennas, Feeds, Impedance matching, Radar antennas, Ultra wideband antennas, Aperture antennas, UWB antennas, directive antennas, waveguide antennas.
    @Article{Elsherbini2012a,
    author = {A. Elsherbini and K. Sarabandi},
    title = {Compact Directive Ultra-Wideband Rectangular Waveguide Based Antenna for Radar and Communication Applications},
    journal = IEEE_J_AP,
    year = {2012},
    volume = {60},
    number = {5},
    month = may,
    pages = {2203--2209},
    issn = {0018-926X},
    doi = {10.1109/TAP.2012.2189727},
    keywords = {UHF antennas, antenna feeds, baluns, microwave antennas, planar antennas, radar antennas, ultra wideband antennas, ultra wideband communication, ultra wideband radar, waveguide antennas, VSWR, aperture field distribution, balun structure, communication applications, compact directive ultra-wideband rectangular waveguide based antenna, cross-polarization performance, directive ultra-wideband antenna, fabrication tolerances, frequency 1.08 GHz to 4.9 GHz, integrated balun design, planar antenna aperture, polarizer, radar applications, rectangular waveguide antenna feeding structure, rectangular waveguide aperture antennas, standard balun, waveguide mode, Apertures, Directive antennas, Feeds, Impedance matching, Radar antennas, Ultra wideband antennas, Aperture antennas, UWB antennas, directive antennas, waveguide antennas},
    owner = {ofrey},
    
    }
    


  8. Gianfranco Fornaro, Diego Reale, and Simona Verde. Potential of SAR for monitoring transportation infrastructures: an analysis with the multi-dimensional imaging technique. Journal of Geophysics and Engineering, 9(4):S1, 2012. Keyword(s): SAR Processing, SAR interferometry, Interferometry, differential interferometry, InSAR, DInSAR, Persistent Scatterer Interferometry, PSI, SAR Tomography, Tomography, Spaceborne SAR, TerraSAR-X, X-band.
    Abstract: Differential interferometric synthetic aperture radar (SAR) has proven to be effective for accurate localization and monitoring of the displacement of ground targets. The high accuracy and spatial density of the measurements make this technique cost effective compared to the classical geodetic techniques typically used in the risk monitoring context. Ground infrastructure monitoring is typically carried out with in situ sensors. The new generation of high-resolution SAR sensors, however, allows one to acquire data sets with a spatial resolution reaching metric/submetric values. Here we investigate the application of a multi-dimensional SAR imaging technique, which is an extension of classical differential interferometric techniques, to very high resolution TerraSAR-X data in order to demonstrate the potential of this technology for monitoring of transportation infrastructures.

    @Article{fornaroRealeVerde2012,
    author = {Gianfranco Fornaro and Diego Reale and Simona Verde},
    title = {Potential of {SAR} for monitoring transportation infrastructures: an analysis with the multi-dimensional imaging technique},
    journal = {Journal of Geophysics and Engineering},
    year = {2012},
    volume = {9},
    number = {4},
    pages = {S1},
    abstract = {Differential interferometric synthetic aperture radar (SAR) has proven to be effective for accurate localization and monitoring of the displacement of ground targets. The high accuracy and spatial density of the measurements make this technique cost effective compared to the classical geodetic techniques typically used in the risk monitoring context. Ground infrastructure monitoring is typically carried out with in situ sensors. The new generation of high-resolution SAR sensors, however, allows one to acquire data sets with a spatial resolution reaching metric/submetric values. Here we investigate the application of a multi-dimensional SAR imaging technique, which is an extension of classical differential interferometric techniques, to very high resolution TerraSAR-X data in order to demonstrate the potential of this technology for monitoring of transportation infrastructures.},
    file = {:fornaroRealeVerde2012.pdf:PDF},
    keywords = {SAR Processing, SAR interferometry, Interferometry, differential interferometry, InSAR, DInSAR,Persistent Scatterer Interferometry, PSI, SAR Tomography, Tomography,Spaceborne SAR, TerraSAR-X,X-band},
    pdf = {../../../docs/fornaroRealeVerde2012.pdf},
    url = {http://stacks.iop.org/1742-2140/9/i=4/a=S1},
    
    }
    


  9. P. Frolind, A. Gustavsson, M. Lundberg, and L. M. H. Ulander. Circular-Aperture VHF-Band Synthetic Aperture Radar for Detection of Vehicles in Forest Concealment. IEEE Transactions on Geoscience and Remote Sensing, 50(4):1329-1339, April 2012. Keyword(s): focusing, image resolution, radar imaging, synthetic aperture radar, VHF devices, circular-aperture VHF-band synthetic aperture radar, vehicles, dense forest concealment, image resolution, object information, signal processing, imaging geometry, high-quality image focusing, contrast optimization, false-alarm rate, detection probability, frequency 20 MHz to 90 MHz, Focusing, Vehicles, Apertures, Radar tracking, Image resolution, Geometry, Circular aperture, forest concealment, synthetic aperture radar (SAR), target detection, very high frequency (VHF).
    Abstract: Circular-aperture synthetic aperture radar (SAR) imaging has been evaluated using the airborne very high frequency (VHF) band Coherent All RAdio BAnd Sensing (CARABAS)-II system (20-90 MHz). Images, as well as results, from detection of vehicles in dense forest concealment have been compared with linear-aperture SAR. Circular-aperture SAR imaging provides higher image resolution and increased object information, but complexity of signal processing and requirements on imaging geometry accuracy increases. The latter is, however, partly mitigated by using low frequencies in the VHF band. A high-quality digital elevation model is used to ensure high-quality image focusing and to avoid distorting object shape. Contrast optimization is used to reduce global focusing errors. The image resolution is observed to be about 1 m2 in agreement with theoretical predictions. Detection performance has been evaluated using image data from a full circular synthetic aperture, i.e., 360 of aspect angle variation. Results, both for single-pass detection (SPD) and change detection (CD), show a considerable advantage compared with detection based on linear-aperture SAR. The detection probability for SPD increases from 0.4 to 0.8 at a false-alarm rate (FAR) of 30/km2. For CD, the detection probability increases from 0.7 to 0.9 at a FAR of 2/km2.

    @Article{frolindGustavssonLundbergUlanderTGRS2012CircularVHFSARForDetectionofVehiclesInForest,
    author = {P. {Frolind} and A. {Gustavsson} and M. {Lundberg} and L. M. H. {Ulander}},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    title = {Circular-Aperture {VHF}-Band Synthetic Aperture Radar for Detection of Vehicles in Forest Concealment},
    year = {2012},
    issn = {1558-0644},
    month = {April},
    number = {4},
    pages = {1329-1339},
    volume = {50},
    abstract = {Circular-aperture synthetic aperture radar (SAR) imaging has been evaluated using the airborne very high frequency (VHF) band Coherent All RAdio BAnd Sensing (CARABAS)-II system (20-90 MHz). Images, as well as results, from detection of vehicles in dense forest concealment have been compared with linear-aperture SAR. Circular-aperture SAR imaging provides higher image resolution and increased object information, but complexity of signal processing and requirements on imaging geometry accuracy increases. The latter is, however, partly mitigated by using low frequencies in the VHF band. A high-quality digital elevation model is used to ensure high-quality image focusing and to avoid distorting object shape. Contrast optimization is used to reduce global focusing errors. The image resolution is observed to be about 1 m2 in agreement with theoretical predictions. Detection performance has been evaluated using image data from a full circular synthetic aperture, i.e., 360 of aspect angle variation. Results, both for single-pass detection (SPD) and change detection (CD), show a considerable advantage compared with detection based on linear-aperture SAR. The detection probability for SPD increases from 0.4 to 0.8 at a false-alarm rate (FAR) of 30/km2. For CD, the detection probability increases from 0.7 to 0.9 at a FAR of 2/km2.},
    doi = {10.1109/TGRS.2011.2166081},
    keywords = {focusing;image resolution;radar imaging;synthetic aperture radar;VHF devices;circular-aperture VHF-band synthetic aperture radar;vehicles;dense forest concealment;image resolution;object information;signal processing;imaging geometry;high-quality image focusing;contrast optimization;false-alarm rate;detection probability;frequency 20 MHz to 90 MHz;Focusing;Vehicles;Apertures;Radar tracking;Image resolution;Geometry;Circular aperture;forest concealment;synthetic aperture radar (SAR);target detection;very high frequency (VHF)},
    owner = {ofrey},
    
    }
    


  10. S. Gernhardt, Xiaoying Cong, M. Eineder, S. Hinz, and R. Bamler. Geometrical Fusion of Multitrack PS Point Clouds. IEEE Geoscience and Remote Sensing Letters, 9(1):38-42, January 2012. Keyword(s): COSMO-SkyMed satellite, TerraSAR-X satellite, geocoded PS geometrical fusion, high-resolution spotlight data, multitrack PS point clouds, nonurban areas, persistent scatterer positions, radar satellites, synthetic aperture radar images, geophysical image processing, remote sensing by radar, synthetic aperture radar;.
    Abstract: Recent radar satellites like TerraSAR-X and COSMO-SkyMed deliver very high resolution synthetic aperture radar images at a spatial resolution of less than 1 m. Persistent scatterer (PS) positions obtained from stacks of high-resolution spotlight data show very much details of buildings and other structures in 3-D due to the enormous amount of PS obtainable from data of this resolution class. As soon as more than one stack covering the same area is available, a combination of the results is eligible. However, geocoded PSs cannot be simply united due to residual offsets in their absolute positions which stem from unknown absolute height values of the different reference points chosen when processing the individual stacks independently. In this letter, two different methods for a geometrical fusion of geocoded PSs from stacks acquired at different aspect and incidence angles are presented. The algorithms are applied to PS interferometry results of both urban and nonurban areas.

    @Article{gernhardtCongEinederHinzBamler2012,
    Title = {Geometrical Fusion of Multitrack PS Point Clouds},
    Author = {Gernhardt, S. and Xiaoying Cong and Eineder, M. and Hinz, S. and Bamler, R.},
    Doi = {10.1109/LGRS.2011.2159190},
    ISSN = {1545-598X},
    Month = jan,
    Number = {1},
    Pages = {38-42},
    Volume = {9},
    Year = {2012},
    Abstract = {Recent radar satellites like TerraSAR-X and COSMO-SkyMed deliver very high resolution synthetic aperture radar images at a spatial resolution of less than 1 m. Persistent scatterer (PS) positions obtained from stacks of high-resolution spotlight data show very much details of buildings and other structures in 3-D due to the enormous amount of PS obtainable from data of this resolution class. As soon as more than one stack covering the same area is available, a combination of the results is eligible. However, geocoded PSs cannot be simply united due to residual offsets in their absolute positions which stem from unknown absolute height values of the different reference points chosen when processing the individual stacks independently. In this letter, two different methods for a geometrical fusion of geocoded PSs from stacks acquired at different aspect and incidence angles are presented. The algorithms are applied to PS interferometry results of both urban and nonurban areas.},
    Journal = {IEEE Geoscience and Remote Sensing Letters},
    Keywords = {COSMO-SkyMed satellite;TerraSAR-X satellite;geocoded PS geometrical fusion;high-resolution spotlight data;multitrack PS point clouds;nonurban areas;persistent scatterer positions;radar satellites;synthetic aperture radar images;geophysical image processing;remote sensing by radar;synthetic aperture radar;} 
    }
    


  11. Kanika Goel and Nico Adam. An advanced algorithm for deformation estimation in non-urban areas. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):100 - 110, 2012. Keyword(s): SAR Processing, Interferometry, SAR Interferometry, InSAR, DInSAR, Adaptive spatial phase filtering, Distributed scatterer (DS), L1-norm minimization, Singular Value Decompostion, SVD, L2-norm minimization, Small Baseline Subset Algorithm, SBAS, TerraSAR-X, Spaceborne SAR, X-band.
    Abstract: This paper presents an advanced differential SAR interferometry stacking algorithm for high resolution deformation monitoring in non-urban areas with a focus on distributed scatterers (DSs). Techniques such as the Small Baseline Subset Algorithm (SBAS) have been proposed for processing DSs. SBAS makes use of small baseline differential interferogram subsets. Singular value decomposition (SVD), i.e. L2 norm minimization is applied to link independent subsets separated by large baselines. However, the interferograms used in SBAS are multilooked using a rectangular window to reduce phase noise caused for instance by temporal decorrelation, resulting in a loss of resolution and the superposition of topography and deformation signals from different objects. Moreover, these have to be individually phase unwrapped and this can be especially difficult in natural terrains. An improved deformation estimation technique is presented here which exploits high resolution SAR data and is suitable for rural areas. The implemented method makes use of small baseline differential interferograms and incorporates an object adaptive spatial phase filtering and residual topography removal for an accurate phase and coherence estimation, while preserving the high resolution provided by modern satellites. This is followed by retrieval of deformation via the SBAS approach, wherein, the phase inversion is performed using an L1 norm minimization which is more robust to the typical phase unwrapping errors encountered in non-urban areas. Meter resolution TerraSAR-X data of an underground gas storage reservoir in Germany is used for demonstrating the effectiveness of this newly developed technique in rural areas

    @Article{goelAdamISPRSJ2012,
    author = {Kanika Goel and Nico Adam},
    title = {An advanced algorithm for deformation estimation in non-urban areas},
    journal = {ISPRS Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {100 - 110},
    issn = {0924-2716},
    abstract = {This paper presents an advanced differential SAR interferometry stacking algorithm for high resolution deformation monitoring in non-urban areas with a focus on distributed scatterers (DSs). Techniques such as the Small Baseline Subset Algorithm (SBAS) have been proposed for processing DSs. SBAS makes use of small baseline differential interferogram subsets. Singular value decomposition (SVD), i.e. L2 norm minimization is applied to link independent subsets separated by large baselines. However, the interferograms used in SBAS are multilooked using a rectangular window to reduce phase noise caused for instance by temporal decorrelation, resulting in a loss of resolution and the superposition of topography and deformation signals from different objects. Moreover, these have to be individually phase unwrapped and this can be especially difficult in natural terrains. An improved deformation estimation technique is presented here which exploits high resolution SAR data and is suitable for rural areas. The implemented method makes use of small baseline differential interferograms and incorporates an object adaptive spatial phase filtering and residual topography removal for an accurate phase and coherence estimation, while preserving the high resolution provided by modern satellites. This is followed by retrieval of deformation via the SBAS approach, wherein, the phase inversion is performed using an L1 norm minimization which is more robust to the typical phase unwrapping errors encountered in non-urban areas. Meter resolution TerraSAR-X data of an underground gas storage reservoir in Germany is used for demonstrating the effectiveness of this newly developed technique in rural areas},
    doi = {10.1016/j.isprsjprs.2012.06.001},
    file = {:goelAdamISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, Interferometry, SAR Interferometry, InSAR, DInSAR, Adaptive spatial phase filtering, Distributed scatterer (DS), L1-norm minimization, Singular Value Decompostion, SVD, L2-norm minimization, Small Baseline Subset Algorithm, SBAS, TerraSAR-X, Spaceborne SAR, X-band},
    pdf = {../../../docs/goelAdamISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612001013},
    
    }
    


  12. Jaime Hueso Gonzlez, John Mohan Walter Antony, Markus Bachmann, Gerhard Krieger, Manfred Zink, Dirk Schrank, and Marco Schwerdt. Bistatic system and baseline calibration in TanDEM-X to ensure the global digital elevation model quality. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):3-11, 2012. Keyword(s): SAR Processing, Accuracy, Calibration, Interferometry, SAR Interferometry, InSAR, DInSAR, TerraSAR-X, Spaceborne SAR, X-band.
    Abstract: TanDEM-X is an operational satellite mission with the goal of generating a high quality global digital elevation model (DEM) based on synthetic aperture radar (SAR) interferometry in X-band. In order to ensure the quality of the DEM, the differential range measurements and knowledge of the interferometric baseline have to be extremely accurate. In this paper, the bistatic system calibration strategy implemented in TanDEM-X to achieve the desired DEM quality will be described, focusing on the baseline calibration procedure. The results of the tests, which were performed in parallel to the operational DEM acquisition, verify the suitability of this approach

    @Article{HuesoGonzalezEtAlISPRSJ2012,
    author = {Jaime Hueso Gonz{\'a}lez and John Mohan Walter Antony and Markus Bachmann and Gerhard Krieger and Manfred Zink and Dirk Schrank and Marco Schwerdt},
    title = {Bistatic system and baseline calibration in {TanDEM-X} to ensure the global digital elevation model quality},
    journal = {ISPRS Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {3-11},
    issn = {0924-2716},
    abstract = {TanDEM-X is an operational satellite mission with the goal of generating a high quality global digital elevation model (DEM) based on synthetic aperture radar (SAR) interferometry in X-band. In order to ensure the quality of the DEM, the differential range measurements and knowledge of the interferometric baseline have to be extremely accurate. In this paper, the bistatic system calibration strategy implemented in TanDEM-X to achieve the desired DEM quality will be described, focusing on the baseline calibration procedure. The results of the tests, which were performed in parallel to the operational DEM acquisition, verify the suitability of this approach},
    doi = {10.1016/j.isprsjprs.2012.05.008},
    file = {:HuesoGonzalezEtAlISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, Accuracy, Calibration, Interferometry, SAR Interferometry, InSAR, DInSAR,TerraSAR-X, Spaceborne SAR, X-band},
    pdf = {../../../docs/HuesoGonzalezEtAlISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612000974},
    
    }
    


  13. Astrid Gruber, Birgit Wessel, Martin Huber, and Achim Roth. Operational TanDEM-X DEM calibration and first validation results. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):39 - 49, 2012. Keyword(s): SAR Processing, SAR interferometry, Interferometry, InSAR, Block adjustment, DEM, Calibration, InSAR, TanDEM-X, Spaceborne SAR, X-band.
    Abstract: In June 2010, the German TanDEM-X satellite was launched. Together with its twin satellite TerraSAR-X it flies in a close formation enabling single-pass SAR interferometry. The primary goal of the TanDEM-X mission is the derivation of a global digital elevation model (DEM) with unprecedented global accuracies of 10m in absolute and 2m in relative height. A significant calibration effort is required to achieve this high quality world-wide. In spite of an intensive instrument calibration and a highly accurate orbit and baseline determination, some systematic height errors like offsets and tilts in the order of some meters remain in the interferometric DEMs and have to be determined and removed during the TanDEM-X DEM calibration. The objective of this article is the presentation of an approach for the estimation of correction parameters for remaining systematic height errors applicable to interferometric height models. The approach is based on a least-squares block adjustment using the elevation of ICESat GLA14 data as ground control points and connecting points of adjacent, overlapping DEMs as tie-points. In the first part its implementation in DLR's ground segment is outlined. In the second part the approach is applied and validated for two of the first TanDEM-X DEM test sites. Therefore, independent reference data, in particular high resolution reference DEMs and GPS tracks, are used. The results show that the absolute height errors of the TanDEM-X DEM are small in these cases, mostly in the order of 1-2m. An additional benefit of the proposed block adjustment method is that it improves the relative accuracy of adjacent DEMs

    @Article{gruberWesselHuberRothISPRSJ2012,
    author = {Astrid Gruber and Birgit Wessel and Martin Huber and Achim Roth},
    title = {Operational {TanDEM-X} DEM calibration and first validation results},
    journal = {ISPRS Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {39 - 49},
    issn = {0924-2716},
    abstract = {In June 2010, the German TanDEM-X satellite was launched. Together with its twin satellite TerraSAR-X it flies in a close formation enabling single-pass SAR interferometry. The primary goal of the TanDEM-X mission is the derivation of a global digital elevation model (DEM) with unprecedented global accuracies of 10m in absolute and 2m in relative height. A significant calibration effort is required to achieve this high quality world-wide. In spite of an intensive instrument calibration and a highly accurate orbit and baseline determination, some systematic height errors like offsets and tilts in the order of some meters remain in the interferometric DEMs and have to be determined and removed during the TanDEM-X DEM calibration. The objective of this article is the presentation of an approach for the estimation of correction parameters for remaining systematic height errors applicable to interferometric height models. The approach is based on a least-squares block adjustment using the elevation of ICESat GLA14 data as ground control points and connecting points of adjacent, overlapping DEMs as tie-points. In the first part its implementation in DLR's ground segment is outlined. In the second part the approach is applied and validated for two of the first TanDEM-X DEM test sites. Therefore, independent reference data, in particular high resolution reference DEMs and GPS tracks, are used. The results show that the absolute height errors of the TanDEM-X DEM are small in these cases, mostly in the order of 1-2m. An additional benefit of the proposed block adjustment method is that it improves the relative accuracy of adjacent DEMs},
    doi = {10.1016/j.isprsjprs.2012.06.002},
    file = {:gruberWesselHuberRothISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, SAR interferometry, Interferometry, InSAR, Block adjustment,DEM,Calibration,InSAR,TanDEM-X,Spaceborne SAR, X-band},
    pdf = {../../../docs/gruberWesselHuberRothISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612001037},
    
    }
    


  14. Yue Huang, Laurant Ferro-Famil, and Andreas Reigber. Under-Foliage Object Imaging Using SAR Tomography and Polarimetric Spectral Estimators. IEEE Trans. Geosci. Remote Sens., 50(6):2213-2225, June 2012. Keyword(s): SAR Processing, SAR Tomography, Tomography.
    Abstract: This paper addresses the imaging of objects located under a forest cover using polarimetric synthetic aperture radar tomography (POLTOMSAR) at L-band. High-resolution spectral estimators, able to accurately discriminate multiple scattering centers in the vertical direction, are used to separate the response of objects and vehicles embedded in a volumetric background. A new polarimetric spectral analysis technique is introduced and is shown to improve the estimation accuracy of the vertical position of both artificial scatterers and natural environments. This approach provides optimal polarimetric features that may be used to further characterize the objects under analysis. The effectiveness of this novel technique for POLTOMSAR is demonstrated using fully polarimetric L-band airborne data sets acquired by the German Aerospace Center (DLR)'s E-SAR system over the test site in Dornstetten, Germany.

    @Article{huangFerroFamilReigberTGRS2012UnderFoliageObjectImagingUsingSARTomoAndPolSpectralEstimators,
    author = {Huang, Yue and Ferro-Famil, Laurant and Reigber, Andreas},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Under-Foliage Object Imaging Using {SAR} Tomography and Polarimetric Spectral Estimators},
    year = {2012},
    issn = {0196-2892},
    month = {jun},
    number = {6},
    pages = {2213--2225},
    volume = {50},
    abstract = {This paper addresses the imaging of objects located under a forest cover using polarimetric synthetic aperture radar tomography (POLTOMSAR) at L-band. High-resolution spectral estimators, able to accurately discriminate multiple scattering centers in the vertical direction, are used to separate the response of objects and vehicles embedded in a volumetric background. A new polarimetric spectral analysis technique is introduced and is shown to improve the estimation accuracy of the vertical position of both artificial scatterers and natural environments. This approach provides optimal polarimetric features that may be used to further characterize the objects under analysis. The effectiveness of this novel technique for POLTOMSAR is demonstrated using fully polarimetric L-band airborne data sets acquired by the German Aerospace Center (DLR)'s E-SAR system over the test site in Dornstetten, Germany.},
    doi = {10.1109/TGRS.2011.2171494},
    keywords = {SAR Processing, SAR Tomography, Tomography},
    publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
    
    }
    


  15. Susanne Kunis and Stefan Kunis. The nonequispaced FFT on graphics processing units. PAMM, 12(1):7-10, 2012. Keyword(s): Non-equispaced Fourier Transform, Non-equispaced FFT, NFFT, Fast Fourier Transform, FFT, CUDA, GPU, CUNFFT.
    Abstract: Without doubt, the fast Fourier transform (FFT) belongs to the algorithms with large impact on science and engineering. By appropriate approximations, this scheme has been generalized for arbitrary spatial sampling points. This so called nonequispaced FFT is the core of the sequential NFFT3 library and we discuss its computational costs in detail. On the other hand, programmable graphics processing units have evolved into highly parallel, multithreaded, manycore processors with enormous computational capacity and very high memory bandwidth. By means of the so called Compute Unified Device Architecture (CUDA), we parallelized the nonequispaced FFT using the CUDA FFT library and a dedicated parallelization of the approximation scheme.

    @Article{kunisKunisPAMM2012NFFTCUDA,
    author = {Kunis, Susanne and Kunis, Stefan},
    title = {The nonequispaced {FFT} on graphics processing units},
    journal = {PAMM},
    year = {2012},
    volume = {12},
    number = {1},
    pages = {7--10},
    issn = {1617-7061},
    abstract = {Without doubt, the fast Fourier transform (FFT) belongs to the algorithms with large impact on science and engineering. By appropriate approximations, this scheme has been generalized for arbitrary spatial sampling points. This so called nonequispaced FFT is the core of the sequential NFFT3 library and we discuss its computational costs in detail. On the other hand, programmable graphics processing units have evolved into highly parallel, multithreaded, manycore processors with enormous computational capacity and very high memory bandwidth. By means of the so called Compute Unified Device Architecture (CUDA), we parallelized the nonequispaced FFT using the CUDA FFT library and a dedicated parallelization of the approximation scheme.},
    doi = {10.1002/pamm.201210003},
    file = {:kunisKunisPAMM2012NFFTCUDA.pdf:PDF},
    keywords = {Non-equispaced Fourier Transform, Non-equispaced FFT, NFFT, Fast Fourier Transform, FFT, CUDA, GPU, CUNFFT},
    pdf = {../../../docs/kunisKunisPAMM2012NFFTCUDA.pdf},
    publisher = {WILEY-VCH Verlag},
    url = {http://dx.doi.org/10.1002/pamm.201210003},
    
    }
    


  16. Hengxing Lan, Langping Li, Hongjiang Liu, and Zhihua Yang. Complex Urban Infrastructure Deformation Monitoring Using High Resolution PSI. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 5(2):643-651, April 2012. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, China, building infrastructures, complex urban infrastructure deformation monitoring, economic center, engineering geological settings, engineering structures, geometries, ground surface subsidence, high resolution PSI, intensive infrastructure development, persistent scatterer interferometry technology, spotlight mode TerraSAR-X images, thermal dilation, transportation infrastructures, urban vulnerability, building, computerised monitoring, deformation, geophysical image processing, remote sensing;.
    Abstract: The rising concern on the urban vulnerability to the intensive infrastructure development requires enabling technologies offering a prompt and accurate monitoring of urban infrastructures deformation. Urban infrastructures vary dramatically both spatially and temporally and their deformation characteristics are complex. We evaluated the potential of high resolution Persistent Scatterer Interferometry (PSI) technology using coherent stacks of Spotlight mode TerraSAR-X images in monitoring the deformations of different types of infrastructures in a new economics center in China. The high density of Persistent Scatterers (PSs) was identified and therefore facilitates analyzing the deformation character of individual structures. All PSs weer categorized by identifying their corresponding ground object so as to enable to characterize deformation pattern of certain type of urban infrastructure. The spatial and temporal varying patterns of the deformations of typical building infrastructures and transportation infrastructures are revealed. They are strongly related to the interactive effects between the types, engineering structures, geometries, engineering geological settings and various loading scenarios. Besides subsidence of the ground surface, thermal dilation of the infrastructure itself might be another factor accounting for the observed deformation of infrastructure. Although the interpretation for the observed deformation patterns could be quite site-specific, high resolution PSI is shown to have the potential to reveal detailed deformation characteristics of complex urban infrastructures at a relatively large scale.

    @Article{lanLiLiuZang2012PSI,
    Title = {Complex Urban Infrastructure Deformation Monitoring Using High Resolution PSI},
    Author = {Hengxing Lan and Langping Li and Hongjiang Liu and Zhihua Yang},
    Doi = {10.1109/JSTARS.2011.2181490},
    ISSN = {1939-1404},
    Month = apr,
    Number = {2},
    Pages = {643-651},
    Volume = {5},
    Year = {2012},
    Abstract = {The rising concern on the urban vulnerability to the intensive infrastructure development requires enabling technologies offering a prompt and accurate monitoring of urban infrastructures deformation. Urban infrastructures vary dramatically both spatially and temporally and their deformation characteristics are complex. We evaluated the potential of high resolution Persistent Scatterer Interferometry (PSI) technology using coherent stacks of Spotlight mode TerraSAR-X images in monitoring the deformations of different types of infrastructures in a new economics center in China. The high density of Persistent Scatterers (PSs) was identified and therefore facilitates analyzing the deformation character of individual structures. All PSs weer categorized by identifying their corresponding ground object so as to enable to characterize deformation pattern of certain type of urban infrastructure. The spatial and temporal varying patterns of the deformations of typical building infrastructures and transportation infrastructures are revealed. They are strongly related to the interactive effects between the types, engineering structures, geometries, engineering geological settings and various loading scenarios. Besides subsidence of the ground surface, thermal dilation of the infrastructure itself might be another factor accounting for the observed deformation of infrastructure. Although the interpretation for the observed deformation patterns could be quite site-specific, high resolution PSI is shown to have the potential to reveal detailed deformation characteristics of complex urban infrastructures at a relatively large scale.},
    Journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
    Keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI, China;building infrastructures;complex urban infrastructure deformation monitoring;economic center;engineering geological settings;engineering structures;geometries;ground surface subsidence;high resolution PSI;intensive infrastructure development;persistent scatterer interferometry technology;spotlight mode TerraSAR-X images;thermal dilation;transportation infrastructures;urban vulnerability;building;computerised monitoring;deformation;geophysical image processing;remote sensing;} 
    }
    


  17. Yake Li, Chang Liu, Yanfei Wang, and Qi Wang. A Robust Motion Error Estimation Method Based on Raw Data. IEEE Trans. Geosci. Remote Sens., 50(7):2780-2790, 2012. Keyword(s): SAR Processing, Autofocus, SAR Autofocus, MoComp, Motion Compensation, curve fitting, geophysical image processing, least squares approximations, motion compensation, radar imaging, remote sensing by radar, synthetic aperture radar, RCMC, aircraft reference track deviations, curve fitting, double phase gradient estimation, filtering method, high order motion errors, high precision navigation system, high resolution airborne SAR systems, high resolution imagery, image processing, image quality, large swath mode, light aircraft SAR platform, motion compensation, motion error estimation method, range cell migration correction, range dependent phase errors, range resolution improvement, raw data, synthetic aperture radar, weighted total least square method, Aircraft, Azimuth, Electronics packaging, Error analysis, Estimation, Robustness, Trajectory, Autofocus, motion error estimation, phase gradient filtering, synthetic aperture radar (SAR), weighted total least square (WTLS) method.
    Abstract: High-resolution airborne synthetic aperture radar (SAR) systems are very sensible to deviations of the aircraft from the reference track. In high-resolution imagery, the improvement of range resolution increases the difficulty of implementing range cell migration correction (RCMC), while a wider synthetic aperture increases the cumulative time of motion errors which will affect the image quality. To enable accurate motion compensation in image processing, a high-precision navigation system is needed. However, in many cases, due to the limit of accuracy of such systems, motion errors are hard to be compensated correctly, causing mainly the resolution decrease in final image. Moreover, in large swath mode, the range-dependent phase errors are difficult to be compensated by using the conventional autofocus algorithm only. In this paper, we propose a robust motion error estimation method based on raw SAR data. To apply this estimation method, we first estimate the double phase gradients in subaperture. Second, a filtering method based on curve fitting was proposed to reduce the phase estimation errors caused by low signal-to-clutter ratio (SCR). Finally, we propose a weighted total least square method to calculate the motion errors using the filtered phase gradients. Because the proposed algorithm is nonparametric, it can estimate high-order motion errors. This is very important for the airborne SAR, particularly the light aircraft SAR platform, due to their more complicated movement in air turbulence. The versatility that the proposed method can be used in any imaging algorithms is another advantage. The processing of large number of raw SAR data shows that the algorithm is as robust and practical as phase gradient autofocus and can generate better focused images.

    @Article{liLiuWangWang2012Autofocus,
    author = {Yake Li and Chang Liu and Yanfei Wang and Qi Wang},
    title = {A Robust Motion Error Estimation Method Based on Raw Data},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2012},
    volume = {50},
    number = {7},
    pages = {2780-2790},
    issn = {0196-2892},
    abstract = {High-resolution airborne synthetic aperture radar (SAR) systems are very sensible to deviations of the aircraft from the reference track. In high-resolution imagery, the improvement of range resolution increases the difficulty of implementing range cell migration correction (RCMC), while a wider synthetic aperture increases the cumulative time of motion errors which will affect the image quality. To enable accurate motion compensation in image processing, a high-precision navigation system is needed. However, in many cases, due to the limit of accuracy of such systems, motion errors are hard to be compensated correctly, causing mainly the resolution decrease in final image. Moreover, in large swath mode, the range-dependent phase errors are difficult to be compensated by using the conventional autofocus algorithm only. In this paper, we propose a robust motion error estimation method based on raw SAR data. To apply this estimation method, we first estimate the double phase gradients in subaperture. Second, a filtering method based on curve fitting was proposed to reduce the phase estimation errors caused by low signal-to-clutter ratio (SCR). Finally, we propose a weighted total least square method to calculate the motion errors using the filtered phase gradients. Because the proposed algorithm is nonparametric, it can estimate high-order motion errors. This is very important for the airborne SAR, particularly the light aircraft SAR platform, due to their more complicated movement in air turbulence. The versatility that the proposed method can be used in any imaging algorithms is another advantage. The processing of large number of raw SAR data shows that the algorithm is as robust and practical as phase gradient autofocus and can generate better focused images.},
    doi = {10.1109/TGRS.2011.2175737},
    file = {:liLiuWangWang2012Autofocus.pdf:PDF},
    keywords = {SAR Processing, Autofocus, SAR Autofocus, MoComp, Motion Compensation, curve fitting;geophysical image processing;least squares approximations;motion compensation;radar imaging;remote sensing by radar;synthetic aperture radar;RCMC;aircraft reference track deviations;curve fitting;double phase gradient estimation;filtering method;high order motion errors;high precision navigation system;high resolution airborne SAR systems;high resolution imagery;image processing;image quality;large swath mode;light aircraft SAR platform;motion compensation;motion error estimation method;range cell migration correction;range dependent phase errors;range resolution improvement;raw data;synthetic aperture radar;weighted total least square method;Aircraft;Azimuth;Electronics packaging;Error analysis;Estimation;Robustness;Trajectory;Autofocus;motion error estimation;phase gradient filtering;synthetic aperture radar (SAR);weighted total least square (WTLS) method},
    pdf = {../../../docs/liLiuWangWang2012Autofocus.pdf},
    
    }
    


  18. Z. W. Li, W. B. Xu, G. C. Feng, J. Hu, C. C. Wang, X. L. Ding, and J. J. Zhu. Correcting atmospheric effects on InSAR with MERIS water vapour data and elevation-dependent interpolation model. Geophysical Journal International, 189(2):898-910, 2012. Keyword(s): SAR Processing, Interferometry, SAR interferometry, differential SAR interferometry, DInSAR, Displacement, Surface Displacement, Atmosphere, APS, MERIS, MERIS water vapour data, water vapour, Image processing, Satellite geodesy, Radar interferometry, Creep and deformation, Wave propagation.
    Abstract: The propagation delay when radar signals travel from the troposphere has been one of the major limitations for the applications of high precision repeat-pass Interferometric Synthetic Aperture Radar (InSAR). In this paper, we first present an elevation-dependent atmospheric correction model for Advanced Synthetic Aperture Radar (ASAR: the instrument aboard the ENVISAT satellite) interferograms with Medium Resolution Imaging Spectrometer (MERIS) integrated water vapour (IWV) data. Then, using four ASAR interferometric pairs over Southern California as examples, we conduct the atmospheric correction experiments with cloud-free MERIS IWV data. The results show that after the correction the rms differences between InSAR and GPS have reduced by 69.6 per cent, 29 per cent, 31.8 per cent and 23.3 per cent, respectively for the four selected interferograms, with an average improvement of 38.4 per cent. Most importantly, after the correction, six distinct deformation areas have been identified, that is, Long Beach, Santa Ana Basin, Pomona, Ontario, San Bernardino and Elsinore basin, with the deformation velocities along the radar line-of-sight (LOS) direction ranging from 20 mm/yr to 30 mm/yr and on average around 25 mm/yr and Santa Fe Springs and Wilmington, with a slightly low deformation rate of about 10 mm/yr along LOS. Finally, through the method of stacking, we generate a mean deformation velocity map of Los Angeles over a period of 5 yr. The deformation is quite consistent with the historical deformation of the area. Thus, using the cloud-free MERIS IWV data correcting synchronized ASAR interferograms can significantly reduce the atmospheric effects in the interferograms and further better capture the ground deformation and other geophysical signals.

    @Article{liXuFengHuWangDingZhuGJI2012InSARAtmosphereMERIS,
    author = {Li, Z. W. and Xu, W. B. and Feng, G. C. and Hu, J. and Wang, C. C. and Ding, X. L. and Zhu, J. J.},
    title = {Correcting atmospheric effects on InSAR with MERIS water vapour data and elevation-dependent interpolation model},
    journal = {Geophysical Journal International},
    year = {2012},
    volume = {189},
    number = {2},
    pages = {898--910},
    issn = {1365-246X},
    abstract = {The propagation delay when radar signals travel from the troposphere has been one of the major limitations for the applications of high precision repeat-pass Interferometric Synthetic Aperture Radar (InSAR). In this paper, we first present an elevation-dependent atmospheric correction model for Advanced Synthetic Aperture Radar (ASAR: the instrument aboard the ENVISAT satellite) interferograms with Medium Resolution Imaging Spectrometer (MERIS) integrated water vapour (IWV) data. Then, using four ASAR interferometric pairs over Southern California as examples, we conduct the atmospheric correction experiments with cloud-free MERIS IWV data. The results show that after the correction the rms differences between InSAR and GPS have reduced by 69.6 per cent, 29 per cent, 31.8 per cent and 23.3 per cent, respectively for the four selected interferograms, with an average improvement of 38.4 per cent. Most importantly, after the correction, six distinct deformation areas have been identified, that is, Long Beach, Santa Ana Basin, Pomona, Ontario, San Bernardino and Elsinore basin, with the deformation velocities along the radar line-of-sight (LOS) direction ranging from 20 mm/yr to 30 mm/yr and on average around 25 mm/yr and Santa Fe Springs and Wilmington, with a slightly low deformation rate of about 10 mm/yr along LOS. Finally, through the method of stacking, we generate a mean deformation velocity map of Los Angeles over a period of 5 yr. The deformation is quite consistent with the historical deformation of the area. Thus, using the cloud-free MERIS IWV data correcting synchronized ASAR interferograms can significantly reduce the atmospheric effects in the interferograms and further better capture the ground deformation and other geophysical signals.},
    doi = {10.1111/j.1365-246X.2012.05432.x},
    file = {:liXuFengHuWangDingZhuGJI2012InSARAtmosphereMERIS.pdf:PDF},
    keywords = {SAR Processing, Interferometry, SAR interferometry, differential SAR interferometry, DInSAR, Displacement, Surface Displacement, Atmosphere, APS, MERIS, MERIS water vapour data, water vapour, Image processing, Satellite geodesy, Radar interferometry, Creep and deformation, Wave propagation},
    pdf = {../../../docs/liXuFengHuWangDingZhuGJI2012InSARAtmosphereMERIS.pdf},
    publisher = {Blackwell Publishing Ltd},
    url = {http://dx.doi.org/10.1111/j.1365-246X.2012.05432.x},
    
    }
    


  19. F. Lombardini and M. Pardini. Superresolution Differential Tomography: Experiments on Identification of Multiple Scatterers in Spaceborne SAR Data. IEEE Trans. Geosci. Remote Sens., 50(4):1117-1129, April 2012. Keyword(s): SAR Processing, SAR Tomography, Tomography.
    Abstract: Interest is growing in the application of coherent processing of synthetic aperture radar (SAR) data to the monitoring of complex urban or infrastructure areas. However, such scenarios are characterized by the layover phenomenon, in the presence of which conventional interferometric SAR techniques degrade or cannot operate. As a consequence, to monitor reliably a high number of ground structures, the identification, i.e., the detection and height and deformation velocity estimation, of both single and multiple scatterers interfering in the same SAR cell can be a key step. This issue is addressed here by means of differential tomography (Diff-Tomo), a recent multibaseline-multitemporal generalized interferometric framework which allows to resolve multiple moving scatterers at different heights in the same cell. In particular, superresolution adaptive Diff-Tomo is extensively tested and augmented with a new information extraction algorithm for the automated identification of the multiple scatterers. Experiments have been carried out with real C-band spaceborne data over urban areas; corresponding results are shown and discussed.

    @Article{lombardiniPardiniTGRS2011,
    author = {Lombardini, F. and Pardini, M.},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Superresolution Differential Tomography: Experiments on Identification of Multiple Scatterers in Spaceborne {SAR} Data},
    year = {2012},
    issn = {0196-2892},
    month = apr,
    number = {4},
    pages = {1117-1129},
    volume = {50},
    abstract = {Interest is growing in the application of coherent processing of synthetic aperture radar (SAR) data to the monitoring of complex urban or infrastructure areas. However, such scenarios are characterized by the layover phenomenon, in the presence of which conventional interferometric SAR techniques degrade or cannot operate. As a consequence, to monitor reliably a high number of ground structures, the identification, i.e., the detection and height and deformation velocity estimation, of both single and multiple scatterers interfering in the same SAR cell can be a key step. This issue is addressed here by means of differential tomography (Diff-Tomo), a recent multibaseline-multitemporal generalized interferometric framework which allows to resolve multiple moving scatterers at different heights in the same cell. In particular, superresolution adaptive Diff-Tomo is extensively tested and augmented with a new information extraction algorithm for the automated identification of the multiple scatterers. Experiments have been carried out with real C-band spaceborne data over urban areas; corresponding results are shown and discussed.},
    doi = {10.1109/TGRS.2011.2164925},
    keywords = {SAR Processing, SAR Tomography, Tomography},
    
    }
    


  20. Mauro Mariotti d'Alessandro and Stefano Tebaldini. Phenomenology of P-Band Scattering From a Tropical Forest Through Three-Dimensional SAR Tomography. IEEE Geosci. Remote Sens. Lett., 9(3):442-446, May 2012. Keyword(s): SAR Processing, SAR Tomography, Tomography, P-Band, Airborne SAR, Paracou, French Guyana, ONERA, SETHI, TropiSAR, ESA.
    Abstract: The aim of this letter is to discuss recent results from the tomographic analysis of the P-band synthetic aperture radar multibaseline data set acquired by ONERA over French Guyana, in the frame of the European Space Agency campaign TropiSAR. Such a data set is characterized by a vertical resolution of about 20 m, whereas forest height ranges from 20 to 40 m. These features make it possible to map the 3-D distribution of the scene complex reflectivity in up to three independent layers by coherent focusing, i.e., without assuming any physical model or employing superresolution techniques. The most relevant features within the observed results are the presence of dihedral-like scattering in the ground layer, which is hardly noticeable in the original single-look complex data, and the substantial invariance of the innermost forest layer to topographic slopes.

    @Article{mariottidAlessandroTebaldiniGRSL2012,
    author = {Mariotti d'Alessandro, Mauro and Tebaldini, Stefano},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    title = {Phenomenology of {P-}Band Scattering From a Tropical Forest Through Three-Dimensional {SAR} Tomography},
    year = {2012},
    issn = {1545-598X},
    month = may,
    number = {3},
    pages = {442-446},
    volume = {9},
    abstract = {The aim of this letter is to discuss recent results from the tomographic analysis of the P-band synthetic aperture radar multibaseline data set acquired by ONERA over French Guyana, in the frame of the European Space Agency campaign TropiSAR. Such a data set is characterized by a vertical resolution of about 20 m, whereas forest height ranges from 20 to 40 m. These features make it possible to map the 3-D distribution of the scene complex reflectivity in up to three independent layers by coherent focusing, i.e., without assuming any physical model or employing superresolution techniques. The most relevant features within the observed results are the presence of dihedral-like scattering in the ground layer, which is hardly noticeable in the original single-look complex data, and the substantial invariance of the innermost forest layer to topographic slopes.},
    doi = {10.1109/LGRS.2011.2170658},
    file = {:mariottidAlessandroTebaldiniGRSL2012.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Tomography,P-Band, Airborne SAR, Paracou, French Guyana, ONERA, SETHI,TropiSAR, ESA},
    pdf = {../../../docs/mariottidAlessandroTebaldiniGRSL2012.pdf},
    
    }
    


  21. Michele Martone, Benjamin Brutigam, Paola Rizzoli, Carolina Gonzalez, Markus Bachmann, and Gerhard Krieger. Coherence evaluation of TanDEM-X interferometric data. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):21 - 29, 2012. Keyword(s): SAR Processing, Interferometry, SAR Interferometry, InSAR, Synthetic Aperture Radar (SAR), Bistatic SAR, Interferometry, Coherence, Digital elevation model, DEM, TanDEM-X, Spaceborne SAR, X-band.
    Abstract: The TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) mission comprises two nearly identical satellites: TerraSAR-X (TSX, launched in 2007), and TanDEM-X (TDX, launched in June 2010). The primary objective of the mission is to generate a worldwide and consistent digital elevation model (DEM) with an unprecedented accuracy. During the first 3 months after its launch, the TDX satellite was tested and calibrated in monostatic configuration with both satellites flying in 20km along-track distance, and it was proven that the system and acquisition performance is almost identical to TSX. Both satellites were then brought into close formation of a few hundred meters distance to begin the bistatic commissioning phase. Since then, TSX and TDX have acted as a large single-pass radar interferometer, which overcomes the limitations imposed by repeat-pass interferometry and allow the acquisition of highly accurate cross- and along-track interferograms. In December 2010, TanDEM-X began with operational global acquisition: bistatic and monostatic SAR images are simultaneously acquired in stripmap mode and processed to interferograms, from which a global DEM is derived. The key parameter in estimating interferometric performance is the coherence, which is deeply evaluated in this paper. The impact of different decorrelation sources as well as the performance stability over time is investigated by means of statistical analyses and dedicated acquisitions on defined test sites, demonstrating the outstanding interferometric capabilities of the TanDEM-X mission

    @Article{MartoneEtAlISPRSJ2012,
    author = {Michele Martone and Benjamin Br{\"a}utigam and Paola Rizzoli and Carolina Gonzalez and Markus Bachmann and Gerhard Krieger},
    title = {Coherence evaluation of TanDEM-X interferometric data},
    journal = {ISPRS Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {21 - 29},
    issn = {0924-2716},
    abstract = {The TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) mission comprises two nearly identical satellites: TerraSAR-X (TSX, launched in 2007), and TanDEM-X (TDX, launched in June 2010). The primary objective of the mission is to generate a worldwide and consistent digital elevation model (DEM) with an unprecedented accuracy. During the first 3 months after its launch, the TDX satellite was tested and calibrated in monostatic configuration with both satellites flying in 20km along-track distance, and it was proven that the system and acquisition performance is almost identical to TSX. Both satellites were then brought into close formation of a few hundred meters distance to begin the bistatic commissioning phase. Since then, TSX and TDX have acted as a large single-pass radar interferometer, which overcomes the limitations imposed by repeat-pass interferometry and allow the acquisition of highly accurate cross- and along-track interferograms. In December 2010, TanDEM-X began with operational global acquisition: bistatic and monostatic SAR images are simultaneously acquired in stripmap mode and processed to interferograms, from which a global DEM is derived. The key parameter in estimating interferometric performance is the coherence, which is deeply evaluated in this paper. The impact of different decorrelation sources as well as the performance stability over time is investigated by means of statistical analyses and dedicated acquisitions on defined test sites, demonstrating the outstanding interferometric capabilities of the TanDEM-X mission},
    doi = {10.1016/j.isprsjprs.2012.06.006},
    file = {:MartoneEtAlISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, Interferometry, SAR Interferometry, InSAR, Synthetic Aperture Radar (SAR), Bistatic SAR, Interferometry, Coherence, Digital elevation model, DEM, TanDEM-X, Spaceborne SAR, X-band},
    pdf = {../../../docs/MartoneEtAlISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612001207},
    
    }
    


  22. B. Minchew, C.E. Jones, and B. Holt. Polarimetric Analysis of Backscatter From the Deepwater Horizon Oil Spill Using L-Band Synthetic Aperture Radar. Geoscience and Remote Sensing, IEEE Transactions on, 50(10):3812-3830, October 2012. Keyword(s): AD 2010 06 23, Bragg scattering mechanism, DWH slick, Gulf of Mexico, L-band synthetic aperture radar, backscatter polarimetric analysis, coherency matrix eigenvalue, deepwater horizon, deepwater horizon oil spill, dielectric constant, entropy parameters, fully-polarimetric uninhabited aerial vehicle, ocean wave spectral components, oil slick, oil volumetric concentration, radar backscatter, sea water, slick detection method, substantial variation parameter, surface scattering analysis, synthetic aperture radar data, backscatter, eigenvalues and eigenfunctions, entropy, marine pollution, matrix algebra, ocean chemistry, ocean waves, oceanographic regions, oceanographic techniques, permittivity, radar interferometry, remote sensing by radar, seawater, synthetic aperture radar;.
    Abstract: We analyze the fully-polarimetric Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) data acquired on June 23, 2010, from two adjacent, overlapping flight tracks that imaged the main oil slick near the Deepwater Horizon (DWH) rig site in the Gulf of Mexico. Our results show that radar backscatter from both clean water and oil in the slick is predominantly from a single surface scatterer, consistent with the tilted Bragg scattering mechanism, across the range of incidence angles from 26 #x00B0; to 60 #x00B0;. We show that the change of backscatter over the main slick is due both to a damping of the ocean wave spectral components by the oil and an effective reduction of the dielectric constant resulting from a mixture of 65-90% oil with water in the surface layer. This shows that synthetic aperture radar can be used to measure the oil volumetric concentration in a thick slick. Using the H/A/ #x03B1; parameters, we show that surface scattering is dominant for oil and water whenever the data are above the noise floor and that the entropy (H) and #x03B1; parameters for the DWH slick are comparable to those from the clean water. The anisotropy, A, parameter shows substantial variation across the oil slick and a significant range-dependent signal whenever the backscatter in all channels is above the instrument noise floor. For slick detection, we find the most reliable indicator to be the major eigenvalue of the coherency matrix, which is approximately equal to the total backscatter power for both oil in the slick and clean sea water.

    @Article{6166389,
    Title = {Polarimetric Analysis of Backscatter From the Deepwater Horizon Oil Spill Using L-Band Synthetic Aperture Radar},
    Author = {Minchew, B. and Jones, C.E. and Holt, B.},
    Doi = {10.1109/TGRS.2012.2185804},
    ISSN = {0196-2892},
    Month = oct,
    Number = {10},
    Pages = {3812-3830},
    Volume = {50},
    Year = {2012},
    Abstract = {We analyze the fully-polarimetric Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) data acquired on June 23, 2010, from two adjacent, overlapping flight tracks that imaged the main oil slick near the Deepwater Horizon (DWH) rig site in the Gulf of Mexico. Our results show that radar backscatter from both clean water and oil in the slick is predominantly from a single surface scatterer, consistent with the tilted Bragg scattering mechanism, across the range of incidence angles from 26 #x00B0; to 60 #x00B0;. We show that the change of backscatter over the main slick is due both to a damping of the ocean wave spectral components by the oil and an effective reduction of the dielectric constant resulting from a mixture of 65-90% oil with water in the surface layer. This shows that synthetic aperture radar can be used to measure the oil volumetric concentration in a thick slick. Using the H/A/ #x03B1; parameters, we show that surface scattering is dominant for oil and water whenever the data are above the noise floor and that the entropy (H) and #x03B1; parameters for the DWH slick are comparable to those from the clean water. The anisotropy, A, parameter shows substantial variation across the oil slick and a significant range-dependent signal whenever the backscatter in all channels is above the instrument noise floor. For slick detection, we find the most reliable indicator to be the major eigenvalue of the coherency matrix, which is approximately equal to the total backscatter power for both oil in the slick and clean sea water.},
    Journal = {Geoscience and Remote Sensing, IEEE Transactions on},
    Keywords = {AD 2010 06 23;Bragg scattering mechanism;DWH slick;Gulf of Mexico;L-band synthetic aperture radar;backscatter polarimetric analysis;coherency matrix eigenvalue;deepwater horizon;deepwater horizon oil spill;dielectric constant;entropy parameters;fully-polarimetric uninhabited aerial vehicle;ocean wave spectral components;oil slick;oil volumetric concentration;radar backscatter;sea water;slick detection method;substantial variation parameter;surface scattering analysis;synthetic aperture radar data;backscatter;eigenvalues and eigenfunctions;entropy;marine pollution;matrix algebra;ocean chemistry;ocean waves;oceanographic regions;oceanographic techniques;permittivity;radar interferometry;remote sensing by radar;seawater;synthetic aperture radar;} 
    }
    


  23. Ricardo D. Monleone, Matteo Pastorino, Joaquim Fortuny-Guasch, Andrea Salvade, Thomas Bartesaghi, Giovanni Bozza, Manuela Maffongelli, Andrea Massimini, Andrea Carbonetti, and Andrea Randazzo. Impact of Background Noise on Dielectric Reconstructions Obtained by a Prototype of Microwave Axial Tomograph. IEEE Transactions on Instrumentation and Measurement, 61(1):140-148, January 2012. Keyword(s): Tomography, Axial Tomography, dielectric measurement, error analysis, interference (signal), microwave imaging, tomography, background noise, dielectric object inspection, dielectric reconstruction, error parameter, interference signal, measurement environment, microwave axial tomograph, Anechoic chambers, Dielectrics, Image reconstruction, Laboratories, Permittivity, Permittivity measurement, Electromagnetic Interference, imaging systems, inverse problems, microwave sensor, microwave tomography, nondestructive testing.
    Abstract: This paper investigates the influence of noise on a microwave axial tomograph developed by some of the authors for the inspection of dielectric objects. In particular, the impact of the measurement environment is considered and the images obtained from data measured in a controlled and an uncontrolled environment are presented and compared. Moreover, the effects of interference signals are considered. Accordingly, several experimental results are reported and discussed in terms of proper error parameters.

    @Article{monleonePastorinoFortunyGuaschSalvadeBartesaghiBozzaMaffongelliMassiminiCarbnettiRandazzoIEEETIM2012MicroWaveAxialTomography,
    author = {Monleone, Ricardo D. and Pastorino, Matteo and Fortuny-Guasch, Joaquim and Salvade, Andrea and Bartesaghi, Thomas and Bozza, Giovanni and Maffongelli, Manuela and Massimini, Andrea and Carbonetti, Andrea and Randazzo, Andrea},
    title = {Impact of Background Noise on Dielectric Reconstructions Obtained by a Prototype of Microwave Axial Tomograph},
    journal = {IEEE Transactions on Instrumentation and Measurement},
    year = {2012},
    volume = {61},
    number = {1},
    pages = {140-148},
    month = {Jan},
    issn = {0018-9456},
    abstract = {This paper investigates the influence of noise on a microwave axial tomograph developed by some of the authors for the inspection of dielectric objects. In particular, the impact of the measurement environment is considered and the images obtained from data measured in a controlled and an uncontrolled environment are presented and compared. Moreover, the effects of interference signals are considered. Accordingly, several experimental results are reported and discussed in terms of proper error parameters.},
    doi = {10.1109/TIM.2011.2159144},
    file = {:monleonePastorinoFortunyGuaschSalvadeBartesaghiBozzaMaffongelliMassiminiCarbnettiRandazzoIEEETIM2012MicroWaveAxialTomography.pdf:PDF},
    keywords = {Tomography, Axial Tomography, dielectric measurement;error analysis;interference (signal);microwave imaging;tomography;background noise;dielectric object inspection;dielectric reconstruction;error parameter;interference signal;measurement environment;microwave axial tomograph;Anechoic chambers;Dielectrics;Image reconstruction;Laboratories;Permittivity;Permittivity measurement;Electromagnetic Interference;imaging systems;inverse problems;microwave sensor;microwave tomography;nondestructive testing},
    pdf = {../../../docs/monleonePastorinoFortunyGuaschSalvadeBartesaghiBozzaMaffongelliMassiminiCarbnettiRandazzoIEEETIM2012MicroWaveAxialTomography.pdf},
    
    }
    


  24. Matteo Nannini, Rolf Scheiber, Ralf Horn, and Alberto Moreira. First 3-D Reconstructions of Targets Hidden Beneath Foliage by Means of Polarimetric SAR Tomography. IEEE Geosci. Remote Sens. Lett., 9(1):60-64, January 2012. Keyword(s): SAR Processing, SAR Tomography, Tomography, 3-D reconstructions, AD 2006 09, Dornstetten test site, E-SAR system, German Aerospace Center, Germany, L-band airborne data, imaging technique, multiple phase center separation, polarimetric SAR tomography, tomographic campaign, volume structure information, geophysical image processing, geophysical techniques, image reconstruction, synthetic aperture radar;.
    Abstract: SAR tomography (SARTom) is an imaging technique that allows multiple phase center separation in the vertical direction, leading to a 3-D reconstruction of the imaged scene. The retrieval of volume structure information (e.g., for forest classification) and the solution of the layover problem are two of the most promising applications. In this letter, SARTom, in combination with polarimetry (PolSARTom), is exploited to image and to extract characteristic features (e.g., shape and height) of targets hidden beneath foliage. This analysis is applied to L-band airborne data acquired by the E-SAR system of the German Aerospace Center (DLR) during a tomographic campaign that took place in September 2006 on the test site of Dornstetten (Germany).

    @Article{nanniniScheiberHornMoreira2012,
    author = {Nannini, Matteo and Scheiber, Rolf and Horn, Ralf and Moreira, Alberto},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    title = {First {3-D} Reconstructions of Targets Hidden Beneath Foliage by Means of Polarimetric {SAR} Tomography},
    year = {2012},
    issn = {1545-598X},
    month = jan,
    number = {1},
    pages = {60-64},
    volume = {9},
    abstract = {SAR tomography (SARTom) is an imaging technique that allows multiple phase center separation in the vertical direction, leading to a 3-D reconstruction of the imaged scene. The retrieval of volume structure information (e.g., for forest classification) and the solution of the layover problem are two of the most promising applications. In this letter, SARTom, in combination with polarimetry (PolSARTom), is exploited to image and to extract characteristic features (e.g., shape and height) of targets hidden beneath foliage. This analysis is applied to L-band airborne data acquired by the E-SAR system of the German Aerospace Center (DLR) during a tomographic campaign that took place in September 2006 on the test site of Dornstetten (Germany).},
    doi = {10.1109/LGRS.2011.2160329},
    keywords = {SAR Processing, SAR Tomography, Tomography,3-D reconstructions;AD 2006 09;Dornstetten test site;E-SAR system;German Aerospace Center;Germany;L-band airborne data;imaging technique;multiple phase center separation;polarimetric SAR tomography;tomographic campaign;volume structure information;geophysical image processing;geophysical techniques;image reconstruction;synthetic aperture radar;},
    
    }
    


  25. Victor D. Navarro-Sanchez and Juan M. Lopez-Sanchez. Improvement of Persistent-Scatterer Interferometry Performance by Means of a Polarimetric Optimization. IEEE Geosci. Remote Sens. Lett., 9(4):609-613, July 2012. Keyword(s): SAR Processing, persistent scatterer interferometry, PSI, urban area, deformation monitoring, polarimetric optimization, Spain, TerraSAR-X, optimization, phase quality, pixel identification, polarimetry, polarization image, airborne radar, artificial satellites, electromagnetic wave scattering, geophysical image processing, optimisation, polarisation, radar imaging, radar interferometry, radar polarimetry, synthetic aperture radar, spaceborne SAR.
    Abstract: This letter is aimed at presenting results confirming the contribution of polarimetry to improve the performance of persistent-scatterer interferometry. The improvement is provided by the identification of more pixels with good phase quality, under criteria commonly employed in this context, after a search in the available polarimetric space. The ground deformation results obtained with a series of 41 dual-polarization images acquired by TerraSAR-X over the metropolitan area of Murcia, Spain, have been used to illustrate this approach.

    @Article{navarroSanchezLopezSanchez2012,
    author = {Navarro-Sanchez, Victor D. and Lopez-Sanchez, Juan M.},
    title = {Improvement of Persistent-Scatterer Interferometry Performance by Means of a Polarimetric Optimization},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2012},
    volume = {9},
    number = {4},
    pages = {609-613},
    month = jul,
    issn = {1545-598X},
    abstract = {This letter is aimed at presenting results confirming the contribution of polarimetry to improve the performance of persistent-scatterer interferometry. The improvement is provided by the identification of more pixels with good phase quality, under criteria commonly employed in this context, after a search in the available polarimetric space. The ground deformation results obtained with a series of 41 dual-polarization images acquired by TerraSAR-X over the metropolitan area of Murcia, Spain, have been used to illustrate this approach.},
    doi = {10.1109/LGRS.2011.2176715},
    file = {:navarroSanchezLopezSanchez2012.pdf:PDF},
    keywords = {SAR Processing, persistent scatterer interferometry, PSI, urban area, deformation monitoring, polarimetric optimization, Spain;TerraSAR-X;optimization;phase quality;pixel identification;polarimetry;polarization image;airborne radar;artificial satellites;electromagnetic wave scattering;geophysical image processing;optimisation;polarisation;radar imaging;radar interferometry;radar polarimetry;synthetic aperture radar;spaceborne SAR},
    pdf = {../../../docs/navarroSanchezLopezSanchez2012.pdf},
    
    }
    


  26. Antonio Pauciullo, Diego Reale, Antonio De Maio, and Gianfranco Fornaro. Detection of Double Scatterers in SAR Tomography. IEEE Transactions on Geoscience and Remote Sensing, 50(9):3567-3586, September 2012. Keyword(s): SAR Processing, double scatterers, Bayesian Information Criterion, Generalized Likelihood Ratio Test, SAR Tomography, differential tomography, double scatterers, ground scatterers, high resolution radar systems, multi-dimensional SAR imaging, scatterers detection, SAR Interferometry, Multidimensional system, Spaceborne SAR, X-Band, Urban, Persistent Scatterer Interferometry, PSI, time series, geophysical image processing, image reconstruction, image resolution, radar imaging, radar interferometry, radar resolution, synthetic aperture radar, 3D reconstruction.
    Abstract: Synthetic aperture radar (SAR) tomography is a technique that extends the concept of SAR interferometry for the accurate localization and monitoring of ground scatterers. Data that are being acquired by the new high resolution SAR sensors offer new perspectives in the 3-D reconstruction and monitoring of urban areas and, particularly, of individual buildings. SAR tomography allows increasing the density of measurements by handling situations where multiple stable scatterers interfere in the same resolution cell. The detection of reliable, i.e., persistent, scatterers is however a challenging issue. In this paper, we investigate three detection approaches: The first is based on a modification of information theoretical criteria; the last two are based on the generalized likelihood ratio test. Theoretical performances are analyzed in details on simulated data, and results of the application to real data from both medium and very high resolution sensors are also provided.

    @Article{pauciulloRealeDeMaioFornaroTGRS2009TomoDoubleScatterer,
    author = {Pauciullo, Antonio and Reale, Diego and De Maio, Antonio and Fornaro, Gianfranco},
    title = {Detection of Double Scatterers in {SAR} Tomography},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2012},
    volume = {50},
    number = {9},
    pages = {3567-3586},
    month = sep,
    issn = {0196-2892},
    abstract = {Synthetic aperture radar (SAR) tomography is a technique that extends the concept of SAR interferometry for the accurate localization and monitoring of ground scatterers. Data that are being acquired by the new high resolution SAR sensors offer new perspectives in the 3-D reconstruction and monitoring of urban areas and, particularly, of individual buildings. SAR tomography allows increasing the density of measurements by handling situations where multiple stable scatterers interfere in the same resolution cell. The detection of reliable, i.e., persistent, scatterers is however a challenging issue. In this paper, we investigate three detection approaches: The first is based on a modification of information theoretical criteria; the last two are based on the generalized likelihood ratio test. Theoretical performances are analyzed in details on simulated data, and results of the application to real data from both medium and very high resolution sensors are also provided.},
    doi = {10.1109/TGRS.2012.2183002},
    file = {:pauciulloRealeDeMaioFornaroTGRS2009TomoDoubleScatterer.pdf:PDF},
    keywords = {SAR Processing, double scatterers,Bayesian Information Criterion;Generalized Likelihood Ratio Test, SAR Tomography, differential tomography;double scatterers;ground scatterers;high resolution radar systems;multi-dimensional SAR imaging;scatterers detection; SAR Interferometry;Multidimensional system; Spaceborne SAR, X-Band, Urban, Persistent Scatterer Interferometry, PSI, time series, geophysical image processing;image reconstruction;image resolution;radar imaging;radar interferometry; radar resolution;synthetic aperture radar;3D reconstruction},
    pdf = {../../../docs/pauciulloRealeDeMaioFornaroTGRS2009TomoDoubleScatterer.pdf},
    
    }
    


  27. D. Perissin and Teng Wang. Repeat-Pass SAR Interferometry With Partially Coherent Targets. IEEE Trans. Geosci. Remote Sens., 50(1):271-280, January 2012. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, SAR Interferometry, InSAR, DInSAR, Interferometry, Coherence, Decorrelation, Dispersion, Indexes, Noise, Pixel, Spatial coherence, displacement measurement, electromagnetic wave scattering, feature extraction, radar imaging, radar interferometry, radar target recognition, spaceborne radar, synthetic aperture radar, 3D location estimation, PS technique, SAR images, SAR interferometry, displacement estimation, electromagnetic signature, extraurban areas, information extraction, multitemporal analysis, partially coherent targets, permanent scatterer technique, radar imaging, spaceborne radar, synthetic aperture radar, Deformation monitoring, digital elevation models (DEMs), synthetic aperture radar interferometry (InSAR), time-series analysis;.
    Abstract: By means of the permanent scatterer (PS) technique, repeated spaceborne synthetic aperture radar (SAR) images with relatively low resolution (about 25 m #x00D7; 5 m for the European Remote Sensing (ERS) and Envisat satellites) can be used to estimate the displacement (1-mm precision) and 3-D location (1-m precision) of targets that show an unchanged electromagnetic signature. The main drawback of the PS technique is the limited spatial density of targets that behave coherently during the whole observation span (hundreds of PSs per square kilometer in urban site and up to few points in vegetated areas). In this paper, we describe a new approach for multitemporal analysis of SAR images that also allows extracting information from partially coherent targets. The basic idea is to loosen the restrictive conditions imposed by the PS technique. The results obtained in different test sites allowed to increase significantly the spatial coverage of the estimate of height and deformation trend, particularly in extraurban areas.

    @Article{perissinWangTGRS2012,
    author = {Perissin, D. and Teng Wang},
    title = {Repeat-Pass {SAR} Interferometry With Partially Coherent Targets},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2012},
    volume = {50},
    number = {1},
    pages = {271-280},
    month = jan,
    issn = {0196-2892},
    abstract = {By means of the permanent scatterer (PS) technique, repeated spaceborne synthetic aperture radar (SAR) images with relatively low resolution (about 25 m #x00D7; 5 m for the European Remote Sensing (ERS) and Envisat satellites) can be used to estimate the displacement (1-mm precision) and 3-D location (1-m precision) of targets that show an unchanged electromagnetic signature. The main drawback of the PS technique is the limited spatial density of targets that behave coherently during the whole observation span (hundreds of PSs per square kilometer in urban site and up to few points in vegetated areas). In this paper, we describe a new approach for multitemporal analysis of SAR images that also allows extracting information from partially coherent targets. The basic idea is to loosen the restrictive conditions imposed by the PS technique. The results obtained in different test sites allowed to increase significantly the spatial coverage of the estimate of height and deformation trend, particularly in extraurban areas.},
    doi = {10.1109/TGRS.2011.2160644},
    file = {:perissinWangTGRS2012.pdf:PDF},
    keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI, SAR Interferometry, InSAR, DInSAR, Interferometry, Coherence;Decorrelation;Dispersion;Indexes;Noise;Pixel;Spatial coherence;displacement measurement;electromagnetic wave scattering;feature extraction;radar imaging;radar interferometry;radar target recognition;spaceborne radar;synthetic aperture radar;3D location estimation;PS technique;SAR images;SAR interferometry;displacement estimation;electromagnetic signature;extraurban areas;information extraction;multitemporal analysis;partially coherent targets;permanent scatterer technique;radar imaging;spaceborne radar;synthetic aperture radar;Deformation monitoring;digital elevation models (DEMs);synthetic aperture radar interferometry (InSAR);time-series analysis;},
    pdf = {../../../docs/perissinWangTGRS2012.pdf},
    
    }
    


  28. Daniele Perissin, Zhiying Wang, and Hui Lin. Shanghai subway tunnels and highways monitoring through Cosmo-SkyMed Persistent Scatterers. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):58-67, 2012. Keyword(s): SAR Processing, Interferometry, SAR Interferometry, InSAR, Persistent Scatterer Interferometry, PSI, COSMO-SkyMed, X-Band, Spaceborne SAR, Urban subsidence monitoring, Subways, Highways, Shanghai.
    Abstract: Synthetic Aperture Radar Interferometry (InSAR) is an alternative technique to obtain measurements of surface displacement providing better spatial resolution and comparable accuracy at an extremely lower cost per area than conventional surveying methods. InSAR is becoming more and more popular in monitoring urban deformations, however, the technique requires advanced tools and high level competence to be successfully applied. In this paper we report important results obtained by analyzing new high resolution SAR data in the Shanghai urban area. The data used in this work have been acquired by the Italian X-band sensor Cosmo-SkyMed. About 1.2 million of individual and independent targets have been detected in 600 sq km, revealing impressive details of the ground surface deformation. Using the SARPROZ InSAR tool and integrating the results with Google Earth, we were able to track subway tunnels recently excavated and several highways. Tunnels are visible due to very localized subsidence of the above surface along their path. On the other hand, highways, standing over the ground, in most cases show higher stability than the surrounding areas. The density of targets is so high to allow studying the profile of the tunnel subsidence, which is very useful to predict building damage. Finally, the identification of targets on high buildings helps checking the stability of high constructions along the subway lines, highlighting possible risky situations.

    @Article{perissinWangLinISPRSJ2012,
    author = {Daniele Perissin and Zhiying Wang and Hui Lin},
    title = {Shanghai subway tunnels and highways monitoring through Cosmo-SkyMed Persistent Scatterers},
    journal = {ISPRS Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {58-67},
    issn = {0924-2716},
    abstract = {Synthetic Aperture Radar Interferometry (InSAR) is an alternative technique to obtain measurements of surface displacement providing better spatial resolution and comparable accuracy at an extremely lower cost per area than conventional surveying methods. InSAR is becoming more and more popular in monitoring urban deformations, however, the technique requires advanced tools and high level competence to be successfully applied. In this paper we report important results obtained by analyzing new high resolution SAR data in the Shanghai urban area. The data used in this work have been acquired by the Italian X-band sensor Cosmo-SkyMed. About 1.2 million of individual and independent targets have been detected in 600 sq km, revealing impressive details of the ground surface deformation. Using the SARPROZ InSAR tool and integrating the results with Google Earth, we were able to track subway tunnels recently excavated and several highways. Tunnels are visible due to very localized subsidence of the above surface along their path. On the other hand, highways, standing over the ground, in most cases show higher stability than the surrounding areas. The density of targets is so high to allow studying the profile of the tunnel subsidence, which is very useful to predict building damage. Finally, the identification of targets on high buildings helps checking the stability of high constructions along the subway lines, highlighting possible risky situations.},
    doi = {10.1016/j.isprsjprs.2012.07.002},
    file = {:perissinWangLinISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, Interferometry, SAR Interferometry, InSAR, Persistent Scatterer Interferometry, PSI, COSMO-SkyMed, X-Band, Spaceborne SAR, Urban subsidence monitoring, Subways, Highways, Shanghai},
    pdf = {../../../docs/perissinWangLinISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612001256},
    
    }
    


  29. P. Prats-Iraola, R. Scheiber, L. Marotti, S. Wollstadt, and A. Reigber. TOPS Interferometry With TerraSAR-X. Geoscience and Remote Sensing, IEEE Transactions on, 50(8):3179-3188, August 2012. Keyword(s): SAR Processing, TOPS, Terrain Observation by Progressive Scans, Doppler radar, geophysical image processing, image registration, radar imaging, radar interferometry, remote sensing by radar, synthetic aperture radar, Doppler centroid, SAR interferometry, TOPS imaging mode, TOPS interferometry, TerraSAR-X, Terrain Observation by Progressive Scans imaging mode, accurate interferometric products, azimuth coregistration performance, burst edges, coregistration accuracy, repeat pass TOPS data, squint effects, stripmap interferometric data, Accuracy, Azimuth, Doppler effect, Electrostatic discharges, Estimation, Orbits, Thyristors, Coregistration, SAR interferometry, TOPS interferometry, synthetic aperture radar (SAR), terrain observation by progressive scans (TOPS).
    @Article{pratsScheiberMarottiWollstadtReigberTGRS2012TOPSINSAR,
    author = {Prats-Iraola, P. and Scheiber, R. and Marotti, L. and Wollstadt, S. and Reigber, A.},
    title = {TOPS Interferometry With TerraSAR-X},
    journal = {Geoscience and Remote Sensing, IEEE Transactions on},
    year = {2012},
    volume = {50},
    number = {8},
    pages = {3179-3188},
    month = {Aug},
    issn = {0196-2892},
    doi = {10.1109/TGRS.2011.2178247},
    file = {:pratsScheiberMarottiWollstadtReigberTGRS2012TOPSINSAR.pdf:PDF},
    keywords = {SAR Processing, TOPS, Terrain Observation by Progressive Scans,Doppler radar;geophysical image processing;image registration;radar imaging;radar interferometry;remote sensing by radar;synthetic aperture radar;Doppler centroid;SAR interferometry;TOPS imaging mode;TOPS interferometry;TerraSAR-X;Terrain Observation by Progressive Scans imaging mode;accurate interferometric products;azimuth coregistration performance;burst edges;coregistration accuracy;repeat pass TOPS data;squint effects;stripmap interferometric data;Accuracy;Azimuth;Doppler effect;Electrostatic discharges;Estimation;Orbits;Thyristors;Coregistration;SAR interferometry;TOPS interferometry;synthetic aperture radar (SAR);terrain observation by progressive scans (TOPS)},
    pdf = {../../../docs/pratsScheiberMarottiWollstadtReigberTGRS2012TOPSINSAR.pdf},
    
    }
    


  30. G. Quin and P. Loreaux. Submillimeter Accuracy of Multipass Corner Reflector Monitoring by PS Technique. IEEE Transactions on Geoscience and Remote Sensing, PP(99):1-9, 2012. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI.
    Abstract: This paper presents the results of an experiment that is performed with a network of bidirectional corner reflector (CR) multipass scattering equipment (MUSE), which enable 3-D-displacement measurements. We describe the results of an experiment which was designed to assess the precision of the measurements of ground displacement using MUSE CRs and the permanent scatterer (PS) technique. The CR displacements are applied by micrometric vernier controls during the acquisition of a TerraSAR-X time series of ten images. The relative displacements are estimated between each date, using a PS technique. This paper shows that the relative displacements between the reflectors are estimated with a precision of 0.48 mm along the line of sight. This precision is defined as the standard deviation of the difference between the measured and the applied displacements along the time series. The linear displacement rates of the reflectors are then estimated using the spatiotemporal unwrapping network algorithm, with a 0.4-mm/year precision. We finally show that the experimental results are well predicted by theorical simulations.

    @Article{quinLoreaux2012,
    author = {Quin, G. and Loreaux, P.},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    title = {Submillimeter Accuracy of Multipass Corner Reflector Monitoring by PS Technique},
    year = {2012},
    issn = {0196-2892},
    number = {99},
    pages = {1-9},
    volume = {PP},
    abstract = {This paper presents the results of an experiment that is performed with a network of bidirectional corner reflector (CR) multipass scattering equipment (MUSE), which enable 3-D-displacement measurements. We describe the results of an experiment which was designed to assess the precision of the measurements of ground displacement using MUSE CRs and the permanent scatterer (PS) technique. The CR displacements are applied by micrometric vernier controls during the acquisition of a TerraSAR-X time series of ten images. The relative displacements are estimated between each date, using a PS technique. This paper shows that the relative displacements between the reflectors are estimated with a precision of 0.48 mm along the line of sight. This precision is defined as the standard deviation of the difference between the measured and the applied displacements along the time series. The linear displacement rates of the reflectors are then estimated using the spatiotemporal unwrapping network algorithm, with a 0.4-mm/year precision. We finally show that the experimental results are well predicted by theorical simulations.},
    doi = {10.1109/TGRS.2012.2206600},
    keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI},
    
    }
    


  31. S.N. Riddick, D.A. Schmidt, and N.I. Deligne. An analysis of terrain properties and the location of surface scatterers from persistent scatterer interferometry. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):50 - 57, 2012. Keyword(s): SAR Processing, Interferometry, SAR Interferometry, InSAR, Persistent Scatterer Interferometry, PSI, StaMPS, Cascades, Three Sisters, LiDAR, Geology, Land cover, Vegetation, Volcanoes.
    Abstract: Standard interferometry poses a challenge in heavily vegetated areas due to decorrelation of the radar signal. To alleviate this problem, we implement StaMPS, a persistent scatterer (PS) technique, to obtain a more spatially complete signal in the Cascade Range of the Pacific Northwest. In addition to comparing the spatial extent of the signal from standard Interferometric Synthetic Aperture Radar (InSAR) and StaMPS, we further analyze the selection of scatterers over several terrain types in the Cascades, and systematically vary StaMPS parameters to minimize the selection of false positives and negatives. Utilizing the best parameters, we correlate the location of persistent scatterers to geologic units, and vegetation density derived from Light Detection and Ranging (LiDAR) data. Our findings indicate that persistent scatterers most frequently occur on young, rough basaltic to andesitic lava flows and to a lesser extent on older, reworked basaltic andesitic lava flows exposed as boulder fields in the forests. Very few or no scatterers were found over water, permanent snowfields, evergreen forest, or unconsolidated pyroclastics. Over 90 percent of the scatterers are located in areas with no or very sparse vegetation cover. Based on surface roughness and the percentage of bare earth within the radar footprint, we are able to predict where PS InSAR is most likely to be successful on natural terrains.

    @Article{riddickSchmidtDeligneISPRSJ2012,
    author = {S.N. Riddick and D.A. Schmidt and N.I. Deligne},
    title = {An analysis of terrain properties and the location of surface scatterers from persistent scatterer interferometry},
    journal = {ISPRS Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {50 - 57},
    issn = {0924-2716},
    abstract = {Standard interferometry poses a challenge in heavily vegetated areas due to decorrelation of the radar signal. To alleviate this problem, we implement StaMPS, a persistent scatterer (PS) technique, to obtain a more spatially complete signal in the Cascade Range of the Pacific Northwest. In addition to comparing the spatial extent of the signal from standard Interferometric Synthetic Aperture Radar (InSAR) and StaMPS, we further analyze the selection of scatterers over several terrain types in the Cascades, and systematically vary StaMPS parameters to minimize the selection of false positives and negatives. Utilizing the best parameters, we correlate the location of persistent scatterers to geologic units, and vegetation density derived from Light Detection and Ranging (LiDAR) data. Our findings indicate that persistent scatterers most frequently occur on young, rough basaltic to andesitic lava flows and to a lesser extent on older, reworked basaltic andesitic lava flows exposed as boulder fields in the forests. Very few or no scatterers were found over water, permanent snowfields, evergreen forest, or unconsolidated pyroclastics. Over 90 percent of the scatterers are located in areas with no or very sparse vegetation cover. Based on surface roughness and the percentage of bare earth within the radar footprint, we are able to predict where PS InSAR is most likely to be successful on natural terrains.},
    doi = {10.1016/j.isprsjprs.2012.05.010},
    file = {:riddickSchmidtDeligneISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, Interferometry, SAR Interferometry, InSAR, Persistent Scatterer Interferometry, PSI, StaMPS, Cascades, Three Sisters, LiDAR, Geology, Land cover, Vegetation, Volcanoes},
    pdf = {../../../docs/riddickSchmidtDeligneISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612000998},
    
    }
    


  32. Paola Rizzoli, Benjamin Brutigam, Thomas Kraus, Michele Martone, and Gerhard Krieger. Relative height error analysis of TanDEM-X elevation data. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):30-38, 2012. Keyword(s): SAR Processing, Interferometry, SAR Interferometry, Digital elevation model, Relative height error, TanDEM-X, Spaceborne SAR, X-band.
    Abstract: The primary objective of the TanDEM-X mission is the generation of a global high resolution digital elevation model (DEM) with single-pass SAR interferometry. Within the mission, the Earth's land masses will be mapped at least twice to achieve relative vertical accuracies in the order of two meters. This paper presents an analysis of the mission performance in terms of the relative height error showing first results obtained from TanDEM-X interferometric data. For critical areas characterized by strong volume decorrelation phenomena or mountainous terrain, different approaches to improve the final height error are investigated as well

    @Article{RizzoliBrautigamKrausMartoneKrieger2012ISPRSJ2012,
    author = {Paola Rizzoli and Benjamin Br{\"a}utigam and Thomas Kraus and Michele Martone and Gerhard Krieger},
    title = {Relative height error analysis of TanDEM-X elevation data},
    journal = {ISPRS Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {30-38},
    issn = {0924-2716},
    abstract = {The primary objective of the TanDEM-X mission is the generation of a global high resolution digital elevation model (DEM) with single-pass SAR interferometry. Within the mission, the Earth's land masses will be mapped at least twice to achieve relative vertical accuracies in the order of two meters. This paper presents an analysis of the mission performance in terms of the relative height error showing first results obtained from TanDEM-X interferometric data. For critical areas characterized by strong volume decorrelation phenomena or mountainous terrain, different approaches to improve the final height error are investigated as well},
    doi = {10.1016/j.isprsjprs.2012.06.004},
    file = {:RizzoliBrautigamKrausMartoneKrieger2012ISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, Interferometry, SAR Interferometry, Digital elevation model, Relative height error, TanDEM-X, Spaceborne SAR, X-band},
    pdf = {../../../docs/RizzoliBrautigamKrausMartoneKrieger2012ISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612001074},
    
    }
    


  33. Marc Rodriguez-Cassola, Pau Prats, D. Schulze, N. Tous-Ramon, U. Steinbrecher, L. Marotti, M. Nannini, M. Younis, P. Lopez-Dekker, M. Zink, A. Reigber, G. Krieger, and A. Moreira. First Bistatic Spaceborne SAR Experiments With TanDEM-X. IEEE Geoscience and Remote Sensing Letters, 9(1):33-37, January 2012. Keyword(s): SAR Processing, Bistatic SAR, calibration, digital elevation models, geophysical equipment, remote sensing by radar, synthetic aperture radar, bistatic spaceborne SAR experiments, TerraSAR-X Add-on for Digital Elevation Measurements, high-resolution interferometric mission, TanDEM-X mission, digital elevation model, Earth surface, SAR interferometry, X-band synthetic aperture radar, quasimonostatic configuration, bistatic SAR system, monostatic commissioning phase, monostatic mode, synchronization information, calibration information, bistatic images, Satellites, Synchronization, Spaceborne radar, Azimuth, Radar imaging, Coherence, Bistatic radar, bistatic SAR processing, spaceborne SAR missions, synthetic aperture radar (SAR), time and phase synchronization.
    Abstract: TanDEM-X (TerraSAR-X Add-on for Digital Elevation Measurements) is a high-resolution interferometric mission with the main goal of providing a global and unprecedentedly accurate digital elevation model of the Earth surface by means of single-pass X-band synthetic aperture radar (SAR) interferometry. Despite its usual quasi-monostatic configuration, TanDEM-X is the first genuinely bistatic SAR system in space. During its monostatic commissioning phase, the system has been mainly operated in pursuit monostatic mode. However, some pioneering bistatic SAR experiments with both satellites commanded in nonnominal modes have been conducted with the main purpose of validating the performance of both space and ground segments in very demanding scenarios. In particular, this letter reports about the first bistatic acquisition and the first single-pass interferometric (mono-/bistatic) acquisition with TanDEM-X, addressing their innovative aspects and focusing on the analysis of the experimental results. Even in the absence of essential synchronization and calibration information, bistatic images and interferograms with similar quality to pursuit monostatic have been obtained.

    @Article{rodriguezCassolaEtAlGRSL2012FirstBistaticSARWithTanDEMX,
    author = {Marc {Rodriguez-Cassola} and Pau {Prats} and D. {Schulze} and N. {Tous-Ramon} and U. {Steinbrecher} and L. {Marotti} and M. {Nannini} and M. {Younis} and P. {Lopez-Dekker} and M. {Zink} and A. {Reigber} and G. {Krieger} and A. {Moreira}},
    title = {First Bistatic Spaceborne SAR Experiments With TanDEM-X},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    year = {2012},
    volume = {9},
    number = {1},
    pages = {33-37},
    month = {Jan},
    issn = {1558-0571},
    abstract = {TanDEM-X (TerraSAR-X Add-on for Digital Elevation Measurements) is a high-resolution interferometric mission with the main goal of providing a global and unprecedentedly accurate digital elevation model of the Earth surface by means of single-pass X-band synthetic aperture radar (SAR) interferometry. Despite its usual quasi-monostatic configuration, TanDEM-X is the first genuinely bistatic SAR system in space. During its monostatic commissioning phase, the system has been mainly operated in pursuit monostatic mode. However, some pioneering bistatic SAR experiments with both satellites commanded in nonnominal modes have been conducted with the main purpose of validating the performance of both space and ground segments in very demanding scenarios. In particular, this letter reports about the first bistatic acquisition and the first single-pass interferometric (mono-/bistatic) acquisition with TanDEM-X, addressing their innovative aspects and focusing on the analysis of the experimental results. Even in the absence of essential synchronization and calibration information, bistatic images and interferograms with similar quality to pursuit monostatic have been obtained.},
    doi = {10.1109/LGRS.2011.2158984},
    keywords = {SAR Processing, Bistatic SAR, calibration;digital elevation models;geophysical equipment;remote sensing by radar;synthetic aperture radar;bistatic spaceborne SAR experiments;TerraSAR-X Add-on for Digital Elevation Measurements;high-resolution interferometric mission;TanDEM-X mission;digital elevation model;Earth surface;SAR interferometry;X-band synthetic aperture radar;quasimonostatic configuration;bistatic SAR system;monostatic commissioning phase;monostatic mode;synchronization information;calibration information;bistatic images;Satellites;Synchronization;Spaceborne radar;Azimuth;Radar imaging;Coherence;Bistatic radar;bistatic SAR processing;spaceborne SAR missions;synthetic aperture radar (SAR);time and phase synchronization},
    owner = {ofrey},
    
    }
    


  34. Cristian Rossi, Fernando Rodriguez Gonzalez, Thomas Fritz, Nestor Yague-Martinez, and Michael Eineder. TanDEM-X calibrated Raw DEM generation. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):12 - 20, 2012. Keyword(s): SAR Processing, Interferometry, SAR Interferometry, InSAR, TanDEM-X, DEM, Raw DEM, SAR stereo-radargrammetry, radargrammetry, Absolute phase offset estimation, DEM calibration.
    Abstract: The TanDEM-X mission successfully started on June 21st 2010 with the launch of the German radar satellite TDX, placed in orbit in close formation with the TerraSAR-X (TSX) satellite, and establishing the first spaceborne bistatic interferometer. The processing of SAR raw data to the Raw DEM is performed by one single processor, the Integrated TanDEM-X Processor (ITP). The quality of the Raw DEM is a fundamental parameter for the mission planning. In this paper, a novel quality indicator is derived. It is based on the comparison of the interferometric measure, the unwrapped phase, and the stereo-radargrammetric measure, the geometrical shifts computed in the coregistration stage. By stating the accuracy of the unwrapped phase, it constitutes a useful parameter for the determination of problematic scenes, which will be resubmitted to the dual baseline phase unwrapping processing chain for the mitigation of phase unwrapping errors. The stereo-radargrammetric measure is also operationally used for the Raw DEM absolute calibration through an accurate estimation of the absolute phase offset. This paper examines the interferometric algorithms implemented for the operational TanDEM-X Raw DEM generation, focusing particularly on its quality assessment and its calibration

    @Article{RossiEtAlISPRSJ2012,
    author = {Cristian Rossi and Fernando Rodriguez Gonzalez and Thomas Fritz and Nestor Yague-Martinez and Michael Eineder},
    title = {{TanDEM-X} calibrated Raw {DEM} generation},
    journal = {ISPRS Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {12 - 20},
    issn = {0924-2716},
    abstract = {The TanDEM-X mission successfully started on June 21st 2010 with the launch of the German radar satellite TDX, placed in orbit in close formation with the TerraSAR-X (TSX) satellite, and establishing the first spaceborne bistatic interferometer. The processing of SAR raw data to the Raw DEM is performed by one single processor, the Integrated TanDEM-X Processor (ITP). The quality of the Raw DEM is a fundamental parameter for the mission planning. In this paper, a novel quality indicator is derived. It is based on the comparison of the interferometric measure, the unwrapped phase, and the stereo-radargrammetric measure, the geometrical shifts computed in the coregistration stage. By stating the accuracy of the unwrapped phase, it constitutes a useful parameter for the determination of problematic scenes, which will be resubmitted to the dual baseline phase unwrapping processing chain for the mitigation of phase unwrapping errors. The stereo-radargrammetric measure is also operationally used for the Raw DEM absolute calibration through an accurate estimation of the absolute phase offset. This paper examines the interferometric algorithms implemented for the operational TanDEM-X Raw DEM generation, focusing particularly on its quality assessment and its calibration},
    doi = {10.1016/j.isprsjprs.2012.05.014},
    file = {:RossiEtAlISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, Interferometry, SAR Interferometry, InSAR, TanDEM-X, DEM, Raw DEM, SAR stereo-radargrammetry, radargrammetry, Absolute phase offset estimation, DEM calibration},
    pdf = {../../../docs/RossiEtAlISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612001062},
    
    }
    


  35. A. Rucci, A. Ferretti, A. Monti Guarnieri, and F. Rocca. Sentinel-1 SAR interferometry applications: The outlook for sub millimeter measurements. Remote Sensing of Environment, 120:156 - 163, 2012. Note: The Sentinel Missions - New Opportunities for Science. Keyword(s): Synthetic Aperture Radar (SAR), INSAR, Permanent scatterers, Ground deformation.
    Abstract: Optical leveling campaigns, tiltmeters, GPS and InSAR are geodetic techniques used to detect and monitor surface deformation phenomena. In particular, InSAR data from satellite radar sensors are gaining increasing attention for their cost-effectiveness and unique technical features, making possible the monitoring of large areas, even revisiting the past. Moreover, more advanced InSAR techniques (PSInSAR?, SqueeSAR?) developed in the last decade are capable of providing millimeter precision, comparable to optical leveling, and a high spatial density of displacement measurements, over long periods of time without need of installing equipment or otherwise accessing the study area. Thanks to the high density and quality of the measurements the PSInSAR data can be successfully used in geophysical inversion, to measure the permeability of oil reservoirs and/or to evaluate the possibilities and risks due to seismic faulting in the sequestration of CO2. In these cases, the precision, the sub weekly frequency of the measurements and the time required for the data to be available are the most important aspects, more relevant than the spatial resolution. Until recently, the main limitation to the application of InSAR was the relatively long revisiting time (24 or 35days) and the quite long waiting period for the delivery of the acquired data. The new Sentinel-1 mission, based on a constellation of two satellites, is expected to reduce such limitations guaranteeing a revisit cycle of 6days on a global scale and in particular over Europe and Canada and providing a high level of service reliability with near-real-time delivery of data within 24h, important for risk management applications. The new X band satellite SAR constellations like Cosmo Skymed and TerraSAR X have also a short revisiting time, from 4 to 11days. However, their coverage is limited to well definite areas, and an expensive decision has to be made if to initiate the observations on any target. Sentinel 1, instead, yields global and costless observations and thus, after the end of the commissioning phase, will always produce present and past ground motion for any target. It's important to underline that the millimeter accuracy, applying the InSAR analysis with Sentinel-1, will be achieved within a shorter observation time frame, thanks to the increased number of acquired images per year (Attema et al. 2010, De Zan et al., 2008). Results from ground based radar show that this improved precision is indeed achievable from C to Ku band, provided that an accurate model of the delay due to atmospheric water vapor is available or that precise reference points are close by.

    @Article{rucciFerrettiMontiGuarnieriRoccaRSE2012Sentinel1InSARAppMillimeterMeasurements,
    author = {A. Rucci and A. Ferretti and A. {Monti Guarnieri} and F. Rocca},
    journal = {Remote Sensing of Environment},
    title = {{Sentinel-1} {SAR} interferometry applications: The outlook for sub millimeter measurements},
    year = {2012},
    issn = {0034-4257},
    note = {The Sentinel Missions - New Opportunities for Science},
    pages = {156 - 163},
    volume = {120},
    abstract = {Optical leveling campaigns, tiltmeters, GPS and InSAR are geodetic techniques used to detect and monitor surface deformation phenomena. In particular, InSAR data from satellite radar sensors are gaining increasing attention for their cost-effectiveness and unique technical features, making possible the monitoring of large areas, even revisiting the past. Moreover, more advanced InSAR techniques (PSInSAR?, SqueeSAR?) developed in the last decade are capable of providing millimeter precision, comparable to optical leveling, and a high spatial density of displacement measurements, over long periods of time without need of installing equipment or otherwise accessing the study area. Thanks to the high density and quality of the measurements the PSInSAR data can be successfully used in geophysical inversion, to measure the permeability of oil reservoirs and/or to evaluate the possibilities and risks due to seismic faulting in the sequestration of CO2. In these cases, the precision, the sub weekly frequency of the measurements and the time required for the data to be available are the most important aspects, more relevant than the spatial resolution. Until recently, the main limitation to the application of InSAR was the relatively long revisiting time (24 or 35days) and the quite long waiting period for the delivery of the acquired data. The new Sentinel-1 mission, based on a constellation of two satellites, is expected to reduce such limitations guaranteeing a revisit cycle of 6days on a global scale and in particular over Europe and Canada and providing a high level of service reliability with near-real-time delivery of data within 24h, important for risk management applications. The new X band satellite SAR constellations like Cosmo Skymed and TerraSAR X have also a short revisiting time, from 4 to 11days. However, their coverage is limited to well definite areas, and an expensive decision has to be made if to initiate the observations on any target. Sentinel 1, instead, yields global and costless observations and thus, after the end of the commissioning phase, will always produce present and past ground motion for any target. It's important to underline that the millimeter accuracy, applying the InSAR analysis with Sentinel-1, will be achieved within a shorter observation time frame, thanks to the increased number of acquired images per year (Attema et al. 2010, De Zan et al., 2008). Results from ground based radar show that this improved precision is indeed achievable from C to Ku band, provided that an accurate model of the delay due to atmospheric water vapor is available or that precise reference points are close by.},
    doi = {https://doi.org/10.1016/j.rse.2011.09.030},
    keywords = {Synthetic Aperture Radar (SAR), INSAR, Permanent scatterers, Ground deformation},
    url = {http://www.sciencedirect.com/science/article/pii/S0034425712000752},
    
    }
    


  36. Alexander Schunert and Uwe Soergel. Grouping of Persistent Scatterers in high-resolution SAR data of urban scenes. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):80 - 88, 2012. Keyword(s): SAR Processing, Interferometry, SAR Interferometry, InSAR, Persistent Scatterer Interferometry, PSI, TerraSAR-X, Spaceborne SAR, Urban, Grouping.
    Abstract: Persistent Scatterer Interferometry (PSI) is a technique to simultaneously estimate surface deformation and 3D structure from stacks of SAR images. It was proposed first about one decade ago to monitor preferably urban areas, where in general the highest numbers of PS are found. At that time no high-resolution satellite SAR data were available. Instead, for example, stacks of ERS imagery were used providing ground range resolution of about 25m. In data of such kind only the strongest PS can be detected, which are usually caused by corner reflectors built by orthogonal building and road planes of considerable size, whereas smaller structures causing weaker ones signal are averaged by clutter or mutually interfere with others in the same resolution cell. Thus, if any, only a few or even just one single PS are found per building. The advent of a new senor generation of systems like TerraSAR-X and COSMO-Skymed in 2007 led to a significant improvement of spatial resolution of about one order of magnitude. This comes along with a dramatic rise of PS density: In some cases tens to hundreds are detected at large buildings, which offers the possibility to monitor even individual urban objects. In addition, especially at building facades the distribution of those PS is often quite regular. A reason for that is the usually rectilinear arrangement of facade structures inducing PS like windows or balconies. Those patterns contain a lot of information about the objects under investigation, which is mostly ignored in current PSI processing schemes. For example, consider a regular structure of windows on a certain fcade of a multi-story building. Assuming the same kind of structure generates one single PS at each window, the phase centers of all scatterers caused by windows of each floor share the same height. This means, we may benefit from such kind of redundancy, for instance, to improve the height estimate by averaging over PS having the same elevation. In this work, we first discuss the regular appearance of PS at urban facades for an urban test scene in TerraSAR-X spotlight mode data. Then, we show how PS analysis could benefit by exploitation of the redundancy due to repetitive patterns of man-made objects. Finally, we propose a PS grouping scheme based on a production system and discuss first results achieved for the test area.

    @Article{schunertSoergelISPRSJ2012,
    author = {Alexander Schunert and Uwe Soergel},
    title = {Grouping of Persistent Scatterers in high-resolution SAR data of urban scenes},
    journal = {ISPRS Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {80 - 88},
    issn = {0924-2716},
    abstract = {Persistent Scatterer Interferometry (PSI) is a technique to simultaneously estimate surface deformation and 3D structure from stacks of SAR images. It was proposed first about one decade ago to monitor preferably urban areas, where in general the highest numbers of PS are found. At that time no high-resolution satellite SAR data were available. Instead, for example, stacks of ERS imagery were used providing ground range resolution of about 25m. In data of such kind only the strongest PS can be detected, which are usually caused by corner reflectors built by orthogonal building and road planes of considerable size, whereas smaller structures causing weaker ones signal are averaged by clutter or mutually interfere with others in the same resolution cell. Thus, if any, only a few or even just one single PS are found per building. The advent of a new senor generation of systems like TerraSAR-X and COSMO-Skymed in 2007 led to a significant improvement of spatial resolution of about one order of magnitude. This comes along with a dramatic rise of PS density: In some cases tens to hundreds are detected at large buildings, which offers the possibility to monitor even individual urban objects. In addition, especially at building facades the distribution of those PS is often quite regular. A reason for that is the usually rectilinear arrangement of facade structures inducing PS like windows or balconies. Those patterns contain a lot of information about the objects under investigation, which is mostly ignored in current PSI processing schemes. For example, consider a regular structure of windows on a certain fcade of a multi-story building. Assuming the same kind of structure generates one single PS at each window, the phase centers of all scatterers caused by windows of each floor share the same height. This means, we may benefit from such kind of redundancy, for instance, to improve the height estimate by averaging over PS having the same elevation. In this work, we first discuss the regular appearance of PS at urban facades for an urban test scene in TerraSAR-X spotlight mode data. Then, we show how PS analysis could benefit by exploitation of the redundancy due to repetitive patterns of man-made objects. Finally, we propose a PS grouping scheme based on a production system and discuss first results achieved for the test area.},
    doi = {10.1016/j.isprsjprs.2012.04.002},
    file = {:schunertSoergelISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, Interferometry, SAR Interferometry, InSAR, Persistent Scatterer Interferometry, PSI, TerraSAR-X, Spaceborne SAR, Urban, Grouping},
    pdf = {../../../docs/schunertSoergelISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612000755},
    
    }
    


  37. Manoochehr Shirzaei and R Brgmann. Topography correlated atmospheric delay correction in radar interferometry using wavelet transforms. Geophysical Research Letters, 39(1), 2012.
    @Article{Shirzaei2012,
    author = {Shirzaei, Manoochehr and B{\"u}rgmann, R},
    title = {Topography correlated atmospheric delay correction in radar interferometry using wavelet transforms},
    year = {2012},
    volume = {39},
    number = {1},
    journal = {Geophysical Research Letters},
    owner = {ofrey},
    publisher = {Wiley Online Library},
    
    }
    


  38. Manoochehr Shirzaei, R Brgmann, O Oncken, TR Walter, P Victor, and O Ewiak. Response of forearc crustal faults to the megathrust earthquake cycle: InSAR evidence from Mejillones Peninsula, Northern Chile. Earth and Planetary Science Letters, 333:157-164, 2012.
    @Article{Shirzaei2012a,
    author = {Shirzaei, Manoochehr and B{\"u}rgmann, R and Oncken, O and Walter, TR and Victor, P and Ewiak, O},
    title = {Response of forearc crustal faults to the megathrust earthquake cycle: InSAR evidence from Mejillones Peninsula, Northern Chile},
    year = {2012},
    volume = {333},
    pages = {157--164},
    journal = {Earth and Planetary Science Letters},
    owner = {ofrey},
    publisher = {Elsevier},
    
    }
    


  39. Marc Simard, Scott Hensley, Marco Lavalle, Ralph Dubayah, Naiara Pinto, and Michelle Hofton. An Empirical Assessment of Temporal Decorrelation Using the Uninhabited Aerial Vehicle Synthetic Aperture Radar over Forested Landscapes. Remote Sensing, 4(4):975-986, 2012. Keyword(s): SAR Processing, Decorrelation, Temporal Decorrelation, Differential Interferometry, DInSAR, SAR Interferometry, Coherence, Airborne SAR, UAVSAR, L-Band.
    Abstract: We present an empirical assessment of the impact of temporal decorrelation on interferometric coherence measured over a forested landscape. A series of repeat-pass interferometric radar images with a zero spatial baseline were collected with UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar), a fully polarimetric airborne L-band radar system. The dataset provided temporal separations of 45 minutes, 2, 7 and 9 days. Coincident airborne lidar and weather data were collected. We theoretically demonstrate that UAVSAR measurement accuracy enables accurate quantification of temporal decorrelation. Data analysis revealed precipitation events to be the main driver of temporal decorrelation over the acquisition period. The experiment also shows temporal decorrelation increases with canopy height, and this pattern was found consistent across forest types and polarization.

    @Article{simardHensleyLavalleDubayahPintoHofton2012TempDecorrelation,
    author = {Simard, Marc and Hensley, Scott and Lavalle, Marco and Dubayah, Ralph and Pinto, Naiara and Hofton, Michelle},
    title = {An Empirical Assessment of Temporal Decorrelation Using the Uninhabited Aerial Vehicle Synthetic Aperture Radar over Forested Landscapes},
    journal = {Remote Sensing},
    year = {2012},
    volume = {4},
    number = {4},
    pages = {975-986},
    issn = {2072-4292},
    abstract = {We present an empirical assessment of the impact of temporal decorrelation on interferometric coherence measured over a forested landscape. A series of repeat-pass interferometric radar images with a zero spatial baseline were collected with UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar), a fully polarimetric airborne L-band radar system. The dataset provided temporal separations of 45 minutes, 2, 7 and 9 days. Coincident airborne lidar and weather data were collected. We theoretically demonstrate that UAVSAR measurement accuracy enables accurate quantification of temporal decorrelation. Data analysis revealed precipitation events to be the main driver of temporal decorrelation over the acquisition period. The experiment also shows temporal decorrelation increases with canopy height, and this pattern was found consistent across forest types and polarization.},
    doi = {10.3390/rs4040975},
    file = {:simardHensleyLavalleDubayahPintoHofton2012TempDecorrelation.pdf:PDF},
    keywords = {SAR Processing, Decorrelation, Temporal Decorrelation, Differential Interferometry, DInSAR, SAR Interferometry, Coherence, Airborne SAR, UAVSAR, L-Band},
    pdf = {../../../docs/simardHensleyLavalleDubayahPintoHofton2012TempDecorrelation.pdf},
    url = {http://www.mdpi.com/2072-4292/4/4/975},
    
    }
    


  40. Thomas K. Sjogren, Viet Thuy Vu, Mats I. Pettersson, A. Gustavsson, and Lars M. H. Ulander. Moving Target Relative Speed Estimation and Refocusing in Synthetic Aperture Radar Images. IEEE Trans. Aerosp. Electron. Syst., 48(3):2426-2436, July 2012. Keyword(s): SAR Processing, Moving Target indication, MTI, compensation, frequency-domain analysis, motion compensation, motion estimation, object detection, radar clutter, radar detection, radar imaging, radar tracking, synthetic aperture radar, ultra wideband radar, SAR imaging, UWB, cell migration, chirp estimator, clutter, frequency domain analysis, moving target refocusing, moving target relative speed estimation, moving target signal, phase compensation, synthetic aperture radar, target acceleration, ultra wideband, Approximation methods, Azimuth, Clutter, Estimation, Focusing, Image resolution, Synthetic aperture radar.
    Abstract: In this paper, a method for moving target relative speed estimation and refocusing based on synthetic aperture radar (SAR) images is derived and tested in simulation and on real data with good results. Furthermore, an approach on how to combine the estimation method with the refocusing method is introduced. The estimation is based on a chirp estimator that operates in the SAR image and the refocusing of the moving target is performed locally using subimages. Focusing of the moving target is achieved in the frequency domain by phase compensation, and therefore makes it even possible to handle large range cell migration in the SAR subimages. The proposed approach is tested in a simulation and also on real ultrawideband (UWB) SAR data with very good results. The estimation method works especially well in connection with low frequency (LF) UWB SAR, where the clutter is well focused and the phase of the smeared moving target signal becomes less distorted. The main limitation of the approach is target accelerations where the distortion increases with the integration time.

    @Article{sjogrenVuPetterssonGustavssonUlander2012MTI,
    Title = {Moving Target Relative Speed Estimation and Refocusing in Synthetic Aperture Radar Images},
    Author = {Sjogren, Thomas K. and Vu, Viet Thuy and Pettersson, Mats I. and Gustavsson, A. and Ulander, Lars M. H.},
    Doi = {10.1109/TAES.2012.6237601},
    ISSN = {0018-9251},
    Month = jul,
    Number = {3},
    Pages = {2426-2436},
    Volume = {48},
    Year = {2012},
    Abstract = {In this paper, a method for moving target relative speed estimation and refocusing based on synthetic aperture radar (SAR) images is derived and tested in simulation and on real data with good results. Furthermore, an approach on how to combine the estimation method with the refocusing method is introduced. The estimation is based on a chirp estimator that operates in the SAR image and the refocusing of the moving target is performed locally using subimages. Focusing of the moving target is achieved in the frequency domain by phase compensation, and therefore makes it even possible to handle large range cell migration in the SAR subimages. The proposed approach is tested in a simulation and also on real ultrawideband (UWB) SAR data with very good results. The estimation method works especially well in connection with low frequency (LF) UWB SAR, where the clutter is well focused and the phase of the smeared moving target signal becomes less distorted. The main limitation of the approach is target accelerations where the distortion increases with the integration time.},
    Journal = {IEEE Trans. Aerosp. Electron. Syst.},
    Keywords = {SAR Processing, Moving Target indication, MTI, compensation;frequency-domain analysis;motion compensation;motion estimation;object detection;radar clutter;radar detection;radar imaging;radar tracking;synthetic aperture radar;ultra wideband radar;SAR imaging;UWB;cell migration;chirp estimator;clutter;frequency domain analysis;moving target refocusing;moving target relative speed estimation;moving target signal;phase compensation;synthetic aperture radar;target acceleration;ultra wideband;Approximation methods;Azimuth;Clutter;Estimation;Focusing;Image resolution;Synthetic aperture radar} 
    }
    


  41. Tazio Strozzi, Charles L. Werner, Andreas Wiesmann, and Urs Wegmuller. Topography Mapping With a Portable Real-Aperture Radar Interferometer. IEEE Geosci. Remote Sens. Lett., 9(2):277-281, March 2012. Keyword(s): SAR Processing, Radar antennas, Radar imaging, Radar remote sensing, Rocks, Spaceborne radar, Surfaces, digital elevation models, glaciology, radar interferometry, rocks, terrain mapping, topography (Earth), AD 2009 08 to 2010 03, Grabengufer rock glacier, Switzerland, digital elevation model, height error standard deviation, ice surface change, instrument design, interferometric phase shift, massive Rhone glacier thinning, portable real-aperture radar interferometer, portable terrestrial radar interferometer, rock glacier destabilization, surface topography, topography mapping, Digital elevation model (DEM), glacier, radar, radar interferometry;.
    Abstract: In this letter, the requirements to derive topography from a portable terrestrial radar interferometer are introduced, the instrument design and the relationship between interferometric phase shift and surface topography are explained, and two examples of topographic maps from measurements at the Rhone glacier and Grabengufer rock glacier in Switzerland are presented. In the first case, an external digital elevation model was used to assess the error of topography mapping with the portable radar interferometer and to analyze ice surface changes of the glacier in the last 14 years. We found that the height error standard deviation is about 3 m within a distance of 2 km from the sensor and observed massive thinning of the Rhone glacier. In the second case, we used the terrestrial radar interferometer in order to measure the height difference between August 2009 and March 2010 over the rock glacier as a consequence of its destabilization.

    @Article{strozziWernerWiesmannWegmullerGRSL2012GPRITopo,
    author = {Strozzi, Tazio and Werner, Charles L. and Wiesmann, Andreas and Wegmuller, Urs},
    title = {Topography Mapping With a Portable Real-Aperture Radar Interferometer},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2012},
    volume = {9},
    number = {2},
    pages = {277-281},
    month = mar,
    issn = {1545-598X},
    abstract = {In this letter, the requirements to derive topography from a portable terrestrial radar interferometer are introduced, the instrument design and the relationship between interferometric phase shift and surface topography are explained, and two examples of topographic maps from measurements at the Rhone glacier and Grabengufer rock glacier in Switzerland are presented. In the first case, an external digital elevation model was used to assess the error of topography mapping with the portable radar interferometer and to analyze ice surface changes of the glacier in the last 14 years. We found that the height error standard deviation is about 3 m within a distance of 2 km from the sensor and observed massive thinning of the Rhone glacier. In the second case, we used the terrestrial radar interferometer in order to measure the height difference between August 2009 and March 2010 over the rock glacier as a consequence of its destabilization.},
    doi = {10.1109/LGRS.2011.2166751},
    file = {:strozziWernerWiesmannWegmullerGRSL2012GPRITopo.pdf:PDF},
    keywords = {SAR Processing, Radar antennas;Radar imaging;Radar remote sensing;Rocks;Spaceborne radar;Surfaces;digital elevation models;glaciology;radar interferometry;rocks;terrain mapping;topography (Earth);AD 2009 08 to 2010 03;Grabengufer rock glacier;Switzerland;digital elevation model;height error standard deviation;ice surface change;instrument design;interferometric phase shift;massive Rhone glacier thinning;portable real-aperture radar interferometer;portable terrestrial radar interferometer;rock glacier destabilization;surface topography;topography mapping;Digital elevation model (DEM);glacier;radar;radar interferometry;},
    owner = {ofrey},
    pdf = {../../../docs/strozziWernerWiesmannWegmullerGRSL2012GPRITopo.pdf},
    
    }
    


  42. Alireza Tabatabaeenejad, Mariko S. Burgin, and Mahta Moghaddam. Potential of L-Band Radar for Retrieval of Canopy and Subcanopy Parameters of Boreal Forests. IEEE Transactions on Geoscience and Remote Sensing, 50(6):2150-2160, June 2012. Keyword(s): calibration, data analysis, forestry, remote sensing by radar, simulated annealing, soil, vegetation mapping, AD 2010 06, Jet Propulsion Laboratory, L-band radar, National Aeronautics and Space Administration, SMAP mission, Uninhabited Aerial Vehicle Synthetic Aperture Radar, absolute retrieval error analysis, calibration method, canopy parameter retrieval, central Canada boreal forests, discrete scatterer radar model, forest structure, forward scattering model, global optimization scheme, inversion method, old black spruce site, old jack pine forests, optimization algorithm, optimization problem, relative retrieval error, scattering mechanisms, simulated annealing, soil moisture information, subcanopy parameter retrieval, surface soil moisture retrieval, synthetic data, vegetation parameters, young jack pine forests, Backscatter, Dielectric constant, L-band, Radar, Scattering, Soil moisture, Vegetation mapping, Allometric relationships, Canadian Experiment for Soil Moisture in 2010 (CanEx-SM10), L-band radar, Soil Moisture Active and Passive (SMAP), boreal forest, canopy, inverse problem, microwave scattering.
    Abstract: In this paper, we study the radar retrieval of soil moisture as well as canopy parameters in a range of boreal forests. The retrieval is formulated as an optimization problem where the difference between data and prediction of a forward scattering model is minimized. The forward model is a discrete scatterer radar model, and the optimization algorithm is a global optimization scheme known as simulated annealing. The inversion method is first applied to synthetic data assuming hypothetical allometric relationships to make the retrieval possible by reducing the number of unknown vegetation parameters. The inversion algorithm is then validated using the data acquired with the National Aeronautics and Space Administration (NASA)/Jet Propulsion Laboratory (JPL) Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) in June 2010 in central Canada boreal forests in support of the prelaunch calibration and validation activities of NASA's Soil Moisture Active and Passive (SMAP) mission. The inversion results for synthetic data show that the absolute retrieval error in soil moisture and relative retrieval error in canopy height are small, while the relative output error in trunk density could be large. The inversion results for actual field data show a great accuracy in soil moisture retrieval for Old Jack Pine and Young Jack Pine forests but show large retrieval errors for many of the radar pixels in the Old Black Spruce site. This paper shows that L-band radar is capable of retrieving surface soil moisture in forests with a high biomass where the forest structure allows soil moisture information to be carried by scattering mechanisms.

    @Article{tabatabaeenejadBurginMoghaddamTGRS2012LBandCanopySubCanopyParamRetrieval,
    author = {Alireza Tabatabaeenejad and Mariko S. Burgin and Mahta Moghaddam},
    title = {Potential of {L}-Band Radar for Retrieval of Canopy and Subcanopy Parameters of Boreal Forests},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2012},
    volume = {50},
    number = {6},
    pages = {2150-2160},
    month = jun,
    issn = {0196-2892},
    abstract = {In this paper, we study the radar retrieval of soil moisture as well as canopy parameters in a range of boreal forests. The retrieval is formulated as an optimization problem where the difference between data and prediction of a forward scattering model is minimized. The forward model is a discrete scatterer radar model, and the optimization algorithm is a global optimization scheme known as simulated annealing. The inversion method is first applied to synthetic data assuming hypothetical allometric relationships to make the retrieval possible by reducing the number of unknown vegetation parameters. The inversion algorithm is then validated using the data acquired with the National Aeronautics and Space Administration (NASA)/Jet Propulsion Laboratory (JPL) Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) in June 2010 in central Canada boreal forests in support of the prelaunch calibration and validation activities of NASA's Soil Moisture Active and Passive (SMAP) mission. The inversion results for synthetic data show that the absolute retrieval error in soil moisture and relative retrieval error in canopy height are small, while the relative output error in trunk density could be large. The inversion results for actual field data show a great accuracy in soil moisture retrieval for Old Jack Pine and Young Jack Pine forests but show large retrieval errors for many of the radar pixels in the Old Black Spruce site. This paper shows that L-band radar is capable of retrieving surface soil moisture in forests with a high biomass where the forest structure allows soil moisture information to be carried by scattering mechanisms.},
    doi = {10.1109/TGRS.2011.2173349},
    file = {:tabatabaeenejadBurginMoghaddamTGRS2012LBandCanopySubCanopyParamRetrieval.pdf:PDF},
    keywords = {calibration;data analysis;forestry;remote sensing by radar;simulated annealing;soil;vegetation mapping;AD 2010 06;Jet Propulsion Laboratory;L-band radar;National Aeronautics and Space Administration;SMAP mission;Uninhabited Aerial Vehicle Synthetic Aperture Radar;absolute retrieval error analysis;calibration method;canopy parameter retrieval;central Canada boreal forests;discrete scatterer radar model;forest structure;forward scattering model;global optimization scheme;inversion method;old black spruce site;old jack pine forests;optimization algorithm;optimization problem;relative retrieval error;scattering mechanisms;simulated annealing;soil moisture information;subcanopy parameter retrieval;surface soil moisture retrieval;synthetic data;vegetation parameters;young jack pine forests;Backscatter;Dielectric constant;L-band;Radar;Scattering;Soil moisture;Vegetation mapping;Allometric relationships;Canadian Experiment for Soil Moisture in 2010 (CanEx-SM10);L-band radar;Soil Moisture Active and Passive (SMAP);boreal forest;canopy;inverse problem;microwave scattering;simulated annealing;soil moisture},
    
    }
    


  43. Stefano Tebaldini and Fabio Rocca. Multibaseline Polarimetric SAR Tomography of a Boreal Forest at P- and L-Bands. IEEE Trans. Geosci. Remote Sens., 50(1):232-246, January 2012. Keyword(s): SAR Processing, SAR Tomography, Tomography, ESA campaign BioSAR, Krycklan River catchment, L-band analysis, Northern Sweden, P-band analysis, PolInSAR approach, algebraic synthesis technique, boreal forest, direct volume backscattering process, ground-volume interaction process, multibaseline polarimetric SAR tomography, multipolarimetric data acquisition, polarimetric analysis, remote sensing, single-baseline data analysis, tomographic analysis, tomographic imaging method, vegetation layer analysis, backscatter, data acquisition, forestry, radar interferometry, radar polarimetry, remote sensing by radar, rivers, synthetic aperture radar, tomography, vegetation mapping;.
    Abstract: Longer wavelength synthetic aperture radars (SARs) are precious in the remote sensing of forested areas, being sensitive to contributions from the whole vegetation layer and from the ground below. The electromagnetic properties of such contributions are retrieved from multipolarimetric acquisitions, whereas their vertical structure is retrieved from multibaseline acquisitions through tomographic imaging. Combining baseline and polarization diversity provides most information, allowing the decomposition of the SAR signal into ground- and volume-only contributions. A formal treatment of this problem is provided with the algebraic synthesis technique, which extends the concepts of PolInSAR. The decomposition, however, is shown to be ambiguous in that different solutions are equally consistent with the data. The main goal of this paper is to discuss this topic in light of the experimental results from a tomographic and polarimetric analysis of the boreal forest within the Krycklan River catchment, Northern Sweden, investigated at P- and L-bands during the ESA campaign BioSAR 2008. Different solutions to the decomposition problem will be discussed by examining the corresponding vertical structures accessible through tomographic techniques. Elements are shown supporting the idea that ground-volume interactions play a nonnegligible role at P-band, and a solution is proposed to isolate contributions from direct volume backscattering. The retrieval of forest top height is discussed as well, leading to the conclusion that such parameter is robust against erroneous choices in the identification of volume-only contributions, thus corroborating the PolInSAR approach for the analysis of single-baseline data.

    @Article{tebaldiniRoccaTGRS2012MultibaselinePolTomoSARBorealForestPBandAndLBand,
    author = {Tebaldini, Stefano and Rocca, Fabio},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Multibaseline Polarimetric {SAR} Tomography of a Boreal Forest at {P-} and {L-}Bands},
    year = {2012},
    issn = {0196-2892},
    month = jan,
    number = {1},
    pages = {232--246},
    volume = {50},
    abstract = {Longer wavelength synthetic aperture radars (SARs) are precious in the remote sensing of forested areas, being sensitive to contributions from the whole vegetation layer and from the ground below. The electromagnetic properties of such contributions are retrieved from multipolarimetric acquisitions, whereas their vertical structure is retrieved from multibaseline acquisitions through tomographic imaging. Combining baseline and polarization diversity provides most information, allowing the decomposition of the SAR signal into ground- and volume-only contributions. A formal treatment of this problem is provided with the algebraic synthesis technique, which extends the concepts of PolInSAR. The decomposition, however, is shown to be ambiguous in that different solutions are equally consistent with the data. The main goal of this paper is to discuss this topic in light of the experimental results from a tomographic and polarimetric analysis of the boreal forest within the Krycklan River catchment, Northern Sweden, investigated at P- and L-bands during the ESA campaign BioSAR 2008. Different solutions to the decomposition problem will be discussed by examining the corresponding vertical structures accessible through tomographic techniques. Elements are shown supporting the idea that ground-volume interactions play a nonnegligible role at P-band, and a solution is proposed to isolate contributions from direct volume backscattering. The retrieval of forest top height is discussed as well, leading to the conclusion that such parameter is robust against erroneous choices in the identification of volume-only contributions, thus corroborating the PolInSAR approach for the analysis of single-baseline data.},
    doi = {10.1109/TGRS.2011.2159614},
    keywords = {SAR Processing, SAR Tomography, Tomography, ESA campaign BioSAR;Krycklan River catchment;L-band analysis;Northern Sweden;P-band analysis;PolInSAR approach;algebraic synthesis technique;boreal forest;direct volume backscattering process;ground-volume interaction process;multibaseline polarimetric SAR tomography;multipolarimetric data acquisition;polarimetric analysis;remote sensing;single-baseline data analysis;tomographic analysis;tomographic imaging method;vegetation layer analysis;backscatter;data acquisition;forestry;radar interferometry;radar polarimetry;remote sensing by radar;rivers;synthetic aperture radar;tomography;vegetation mapping;},
    publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
    
    }
    


  44. Viet Thuy Vu, Thomas K. Sjogren, and Mats I. Pettersson. On Synthetic Aperture Radar Azimuth and Range Resolution Equations. IEEE Trans. Aerosp. Electron. Syst., 48(2):1764-1769, April 2012. Keyword(s): SAR Processing, image resolution, integration, radar imaging, radar resolution, synthetic aperture radar, transient response, ultra wideband radar, HPBW, IRF-NSAR-sinc function, IRF-USAR, NB SAR imaging, UWB SAR imaging, half power beamwidth, impulse response function, integration angle, intensity interval, narrow-band-narrow-beam SAR, range resolution equation, signal fractional bandwidth, spatial resolution equation, synthetic aperture radar azimuth, ultrawide-band-ultrawide-beam synthetic aperture radar, Approximation methods, Azimuth, Bandwidth, Equations, Niobium, Spatial resolution.
    Abstract: This paper discusses spatial resolutions for ultrawide-band-ultrawide-beam (UWB) synthetic aperture radar (SAR) in comparison to narrow-band-narrow-beam (NB) SAR. The study shows that in the intensity interval from -6 dB to 0 dB, the behavior of the impulse response function in NB SAR imaging (IRF-NSAR)-sinc function-and the impulse response function in UWB SAR imaging (IRF-USAR) in azimuth and range are similar. This similarity is utilized in a derivation of new spatial resolution equations for UWB SAR based on -3 dB width or half power beamwidth (HPBW). Signal fractional bandwidth and associated integration angle are shown to affect the behavior of IRF-USAR. The effects to HPBW are described by the so-called HPBW narrowing/broadening factors.

    @Article{vuSjogrenPettersson2012RgAziResolutionEq,
    Title = {On Synthetic Aperture Radar Azimuth and Range Resolution Equations},
    Author = {Vu, Viet Thuy and Sjogren, Thomas K. and Pettersson, Mats I.},
    Doi = {10.1109/TAES.2012.6178096},
    ISSN = {0018-9251},
    Month = apr,
    Number = {2},
    Pages = {1764-1769},
    Volume = {48},
    Year = {2012},
    Abstract = {This paper discusses spatial resolutions for ultrawide-band-ultrawide-beam (UWB) synthetic aperture radar (SAR) in comparison to narrow-band-narrow-beam (NB) SAR. The study shows that in the intensity interval from -6 dB to 0 dB, the behavior of the impulse response function in NB SAR imaging (IRF-NSAR)-sinc function-and the impulse response function in UWB SAR imaging (IRF-USAR) in azimuth and range are similar. This similarity is utilized in a derivation of new spatial resolution equations for UWB SAR based on -3 dB width or half power beamwidth (HPBW). Signal fractional bandwidth and associated integration angle are shown to affect the behavior of IRF-USAR. The effects to HPBW are described by the so-called HPBW narrowing/broadening factors.},
    Journal = {IEEE Trans. Aerosp. Electron. Syst.},
    Keywords = {SAR Processing, image resolution;integration;radar imaging;radar resolution;synthetic aperture radar;transient response;ultra wideband radar;HPBW;IRF-NSAR-sinc function;IRF-USAR;NB SAR imaging;UWB SAR imaging;half power beamwidth;impulse response function;integration angle;intensity interval;narrow-band-narrow-beam SAR;range resolution equation;signal fractional bandwidth;spatial resolution equation;synthetic aperture radar azimuth;ultrawide-band-ultrawide-beam synthetic aperture radar;Approximation methods;Azimuth;Bandwidth;Equations;Niobium;Spatial resolution} 
    }
    


  45. Ling Wang, M. Cheney, and B. Borden. Multistatic Radar Imaging of Moving Targets. IEEE Transactions on Aerospace and Electronic Systems, 48(1):230 -242, jan. 2012. Keyword(s): Doppler SAR, filtered backprojection, inverse synthetic aperture radar, linearized imaging theory, matched filtering, moving target, moving target tomography, multistatic radar imaging, narrowband waveform, object distribution, phase space imaging distribution, phase-space imaging formula, phase-space point-spread function, range-Doppler imaging, scattered wave spectral aspect, speed of light, undergoing linear motion, Doppler radar, geometry, image sensors, phase space methods, radar imaging, scattering, synthetic aperture radar, target tracking, tomography;.
    Abstract: We develop a linearized imaging theory that combines the spatial, temporal, and spectral aspects of scattered waves. We consider the case of fixed sensors and a general distribution of objects, each undergoing linear motion; thus the theory deals with imaging distributions in phase space. We derive a model for the data that is appropriate for narrowband waveforms in the case when the targets are moving slowly relative to the speed of light. From this model, we develop a phase-space imaging formula that can be interpreted in terms of filtered backprojection or matched filtering. For this imaging approach, we derive the corresponding phase-space point-spread function (PSF). We show plots of the phase-space point-spread function for various geometries. We also show that in special cases, the theory reduces to: 1) range-Doppler imaging, 2) inverse synthetic aperture radar (ISAR), 3) synthetic aperture radar (SAR), 4) Doppler SAR, and 5) tomography of moving targets.

    @Article{6129632,
    author = {Ling Wang and Cheney, M. and Borden, B.},
    journal = {IEEE Transactions on Aerospace and Electronic Systems},
    title = {Multistatic Radar Imaging of Moving Targets},
    year = {2012},
    issn = {0018-9251},
    month = {jan.},
    number = {1},
    pages = {230 -242},
    volume = {48},
    abstract = {We develop a linearized imaging theory that combines the spatial, temporal, and spectral aspects of scattered waves. We consider the case of fixed sensors and a general distribution of objects, each undergoing linear motion; thus the theory deals with imaging distributions in phase space. We derive a model for the data that is appropriate for narrowband waveforms in the case when the targets are moving slowly relative to the speed of light. From this model, we develop a phase-space imaging formula that can be interpreted in terms of filtered backprojection or matched filtering. For this imaging approach, we derive the corresponding phase-space point-spread function (PSF). We show plots of the phase-space point-spread function for various geometries. We also show that in special cases, the theory reduces to: 1) range-Doppler imaging, 2) inverse synthetic aperture radar (ISAR), 3) synthetic aperture radar (SAR), 4) Doppler SAR, and 5) tomography of moving targets.},
    doi = {10.1109/TAES.2012.6129632},
    keywords = {Doppler SAR;filtered backprojection;inverse synthetic aperture radar;linearized imaging theory;matched filtering;moving target;moving target tomography;multistatic radar imaging;narrowband waveform;object distribution;phase space imaging distribution;phase-space imaging formula;phase-space point-spread function;range-Doppler imaging;scattered wave spectral aspect;speed of light;undergoing linear motion;Doppler radar;geometry;image sensors;phase space methods;radar imaging;scattering;synthetic aperture radar;target tracking;tomography;},
    
    }
    


  46. Yuanyuan Wang, Xiao Xiang Zhu, and Richard Bamler. Retrieval of phase history parameters from distributed scatterers in urban areas using very high resolution SAR data. ISPRS Journal of Photogrammetry and Remote Sensing, 73(0):89 - 99, 2012. Keyword(s): SAR Processing, Interferometry, SAR Interferometry, InSAR, Persistent Scatterer Interferometry, PSI, Phase history, Distributed scatterer, Covariance matrix, TerraSAR-X, Spaceborne SAR.
    Abstract: In a recent contribution Ferretti and co-workers (Ferretti, A., Fumagalli, A., Novali, F., Prati, C., Rocca, F., Rucci, A., 2011. A new algorithm for processing interferometric data-stacks: SqueeSAR IEEE Transactions on Geoscience and Remote Sensing 49(9), pp. 3460-3470) have proposed the SqueeSAR method, a way to exploit temporally coherent distributed scatterers in coherent SAR data stacks. Elevation and deformation or subsidence estimates are obtained with accuracy similar as in the well known persistent scatterer interferometry (PSI). In this paper we propose an alternative approach and provide a first demonstration of the optimal estimation of distributed scatterers' phase histories in urban areas. Different to SqueeSAR, we derive phase histories for each distributed scatterer pixel rather than for groups of pixels. We use the Anderson-Darling statistical test to identify neighboring samples of the same distribution. Prior to covariance matrix estimation required for maximum likelihood estimation we apply a multi-resolution defringe technique. By using TerraSAR-X high resolution spotlight data, it is demonstrated that we are able to retrieve reliable phase histories and motion parameter estimates from distributed scatterers with signal-to-noise-ratio far below the common range.

    @Article{wangZhuBamlerISPRSJ2012,
    author = {Yuanyuan Wang and Xiao Xiang Zhu and Richard Bamler},
    title = {Retrieval of phase history parameters from distributed scatterers in urban areas using very high resolution {SAR} data},
    journal = {{ISPRS} Journal of Photogrammetry and Remote Sensing},
    year = {2012},
    volume = {73},
    number = {0},
    pages = {89 - 99},
    issn = {0924-2716},
    abstract = {In a recent contribution Ferretti and co-workers (Ferretti, A., Fumagalli, A., Novali, F., Prati, C., Rocca, F., Rucci, A., 2011. A new algorithm for processing interferometric data-stacks: SqueeSAR IEEE Transactions on Geoscience and Remote Sensing 49(9), pp. 3460-3470) have proposed the SqueeSAR method, a way to exploit temporally coherent distributed scatterers in coherent SAR data stacks. Elevation and deformation or subsidence estimates are obtained with accuracy similar as in the well known persistent scatterer interferometry (PSI). In this paper we propose an alternative approach and provide a first demonstration of the optimal estimation of distributed scatterers' phase histories in urban areas. Different to SqueeSAR, we derive phase histories for each distributed scatterer pixel rather than for groups of pixels. We use the Anderson-Darling statistical test to identify neighboring samples of the same distribution. Prior to covariance matrix estimation required for maximum likelihood estimation we apply a multi-resolution defringe technique. By using TerraSAR-X high resolution spotlight data, it is demonstrated that we are able to retrieve reliable phase histories and motion parameter estimates from distributed scatterers with signal-to-noise-ratio far below the common range.},
    doi = {10.1016/j.isprsjprs.2012.06.007},
    file = {:wangZhuBamlerISPRSJ2012.pdf:PDF},
    keywords = {SAR Processing, Interferometry, SAR Interferometry, InSAR, Persistent Scatterer Interferometry, PSI, Phase history, Distributed scatterer, Covariance matrix, TerraSAR-X, Spaceborne SAR},
    pdf = {../../../docs/wangZhuBamlerISPRSJ2012.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271612001219},
    
    }
    


  47. Urs Wegmuller, Tazio Strozzi, Andreas Wiesmann, Charles L. Werner, Othmar Frey, Rafael Caduff, and Andrew Kos. Hangrutschungskartierung mittels Radar Interferometrie. Geomatik Schweiz, 110(9), 2012.
    Abstract: Insbesondere durch die ERS-1, ERS-2 und ENVISAT ASAR Sensoren der Europ{\"a}ischen Raumfahrtsagentur ESA hat sich in den letzten 20 Jahren die SAR Interferometrie Methode sehr stark entwickelt. Ein wichtiger Anwendungsbereich ist die Kartierung von Gel{\"a}ndebewegungen. Innerhalb der Schweiz wird die SAR Interferometrie Methodevor allem f{\"u}r die Kartierung von Hangrutschungen eingesetzt. Hangrutschungsinformation wird momentan f{\"u}r die Erstellung der Gefahrenhinweiskarten durch die Kantone ben{\"o}tigt. Angesichts einer wahrscheinlichen Zunahme der Hangrutschungs- undFelssturzgefahren durch die Klimaerw{\"a}rmung und daraus resultierenden sekund{\"a}renVer{\"a}nderungen, wie der Reduktion des Alpinen Permafrosts und des Gletscherr{\"u}ckzugs, kann mit einem zunehmenden Informationsbedarf gerechnet werden.

    @Article{wegmullerStrozziWiesmannWernerFreyCaduffKosGEOMATIK2012DInSAR,
    author = {Wegmuller, Urs and Strozzi, Tazio and Wiesmann, Andreas and Werner, Charles L. and Frey, Othmar and Caduff, Rafael and Kos, Andrew},
    title = {Hangrutschungskartierung mittels {R}adar {I}nterferometrie},
    journal = {Geomatik Schweiz},
    year = {2012},
    volume = {110},
    number = {9},
    abstract = {Insbesondere durch die ERS-1, ERS-2 und ENVISAT ASAR Sensoren der Europ{\"a}ischen Raumfahrtsagentur ESA hat sich in den letzten 20 Jahren die SAR Interferometrie Methode sehr stark entwickelt. Ein wichtiger Anwendungsbereich ist die Kartierung von Gel{\"a}ndebewegungen. Innerhalb der Schweiz wird die SAR Interferometrie Methodevor allem f{\"u}r die Kartierung von Hangrutschungen eingesetzt. Hangrutschungsinformation wird momentan f{\"u}r die Erstellung der Gefahrenhinweiskarten durch die Kantone ben{\"o}tigt. Angesichts einer wahrscheinlichen Zunahme der Hangrutschungs- undFelssturzgefahren durch die Klimaerw{\"a}rmung und daraus resultierenden sekund{\"a}renVer{\"a}nderungen, wie der Reduktion des Alpinen Permafrosts und des Gletscherr{\"u}ckzugs, kann mit einem zunehmenden Informationsbedarf gerechnet werden.},
    file = {:wegmullerStrozziWiesmannWernerFreyCaduffKosGEOMATIK2012DInSAR.pdf:PDF},
    owner = {ofrey},
    url = {http://doi.org/10.5169/seals-309305},
    
    }
    


  48. Steffen Wollstadt, Pau Prats, Markus Bachmann, Josef Mittermayer, and Rolf Scheiber. Scalloping Correction in TOPS Imaging Mode SAR Data. IEEE Geosci. Remote Sens. Lett., 9(4):614-618, July 2012. Keyword(s): SAR Processing, TOPS, Terrain Observation by Progressive Scans, antenna phased arrays, beam steering, calibration, geophysical image processing, phased array radar, radar antennas, radar imaging, synthetic aperture radar, terrain mapping, TOPS imaging mode, TSX, TerraSAR-X antenna model, calibration, electronic beam steering, general cardinal sine antenna model, phased array antenna, scalloping correction, scalloping simulation, synthetic aperture radar, terrain observation by progressive scan, Antennas, Arrays, Azimuth, Beam steering, Calibration, Imaging, Quantization, Electronic beam steering, TOPS calibration, TerraSAR-X (TSX), Terrain Observation by Progressive Scan (TOPS), phased array antenna, scalloping.
    Abstract: This letter presents an investigation on scalloping correction in the Terrain Observation by Progressive Scan (TOPS) imaging mode for synthetic aperture radar systems with electronically steered phased array antennas. A theoretical simulation of the scalloping is performed, and two correction methods are introduced. The simulation is based on a general cardinal sine (sinc) antenna model as well as on the TerraSAR-X (TSX) antenna model. Real TSX data acquired over rainforest are used for demonstration and verification of the scalloping simulation and correction. Furthermore, a calibration approach, taking into account the special TOPS imaging mode properties, is introduced.

    @Article{wollstadtPratsBachmannMittermayerScheiberGRSL2012TOPScalloping,
    author = {Wollstadt, Steffen and Prats, Pau and Bachmann, Markus and Mittermayer, Josef and Scheiber, Rolf},
    title = {Scalloping Correction in {TOPS} Imaging Mode {SAR} Data},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2012},
    volume = {9},
    number = {4},
    pages = {614-618},
    month = {July},
    issn = {1545-598X},
    abstract = {This letter presents an investigation on scalloping correction in the Terrain Observation by Progressive Scan (TOPS) imaging mode for synthetic aperture radar systems with electronically steered phased array antennas. A theoretical simulation of the scalloping is performed, and two correction methods are introduced. The simulation is based on a general cardinal sine (sinc) antenna model as well as on the TerraSAR-X (TSX) antenna model. Real TSX data acquired over rainforest are used for demonstration and verification of the scalloping simulation and correction. Furthermore, a calibration approach, taking into account the special TOPS imaging mode properties, is introduced.},
    doi = {10.1109/LGRS.2011.2176716},
    file = {:wollstadtPratsBachmannMittermayerScheiberGRSL2012TOPScalloping.pdf:PDF},
    keywords = {SAR Processing, TOPS, Terrain Observation by Progressive Scans,antenna phased arrays;beam steering;calibration;geophysical image processing;phased array radar;radar antennas;radar imaging;synthetic aperture radar;terrain mapping;TOPS imaging mode;TSX;TerraSAR-X antenna model;calibration;electronic beam steering;general cardinal sine antenna model;phased array antenna;scalloping correction;scalloping simulation;synthetic aperture radar;terrain observation by progressive scan;Antennas;Arrays;Azimuth;Beam steering;Calibration;Imaging;Quantization;Electronic beam steering;TOPS calibration;TerraSAR-X (TSX);Terrain Observation by Progressive Scan (TOPS);phased array antenna;scalloping},
    pdf = {../../../docs/wollstadtPratsBachmannMittermayerScheiberGRSL2012TOPScalloping.pdf},
    
    }
    


  49. S. Xilong, Y. Anxi, D. Zhen, and L. Diannong. Three-Dimensional SAR Focusing via Compressive Sensing: The Case Study of Angel Stadium. IEEE Geosci. Remote Sens. Lett., PP(99):1-5, 2012.
    Abstract: Recently, a synthetic aperture radar (SAR) tomograhic focusing method based on compressive sensing was proposed. This focusing method can reduce the required number of measurements and achieve satisfying elevation resolving ability. First, we briefly review this novel focusing method and prove the applicability of compressed sensing (CS) for SAR tomography theoretically using the latest improvement of CS. Then, we apply this focusing method to the 3-D reconstruction of Angel Stadium with Envisat-ASAR data. Both the theoretical analysis and satisfying results of real data processing confirmed the applicability of this SAR tomograhic focusing method.

    @Article{6156739,
    author = {Xilong, S. and Anxi, Y. and Zhen, D. and Diannong, L.},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    title = {Three-Dimensional {SAR} Focusing via Compressive Sensing: The Case Study of {A}ngel {S}tadium},
    year = {2012},
    issn = {1545-598X},
    number = {99},
    pages = {1-5},
    volume = {PP},
    abstract = {Recently, a synthetic aperture radar (SAR) tomograhic focusing method based on compressive sensing was proposed. This focusing method can reduce the required number of measurements and achieve satisfying elevation resolving ability. First, we briefly review this novel focusing method and prove the applicability of compressed sensing (CS) for SAR tomography theoretically using the latest improvement of CS. Then, we apply this focusing method to the 3-D reconstruction of Angel Stadium with Envisat-ASAR data. Both the theoretical analysis and satisfying results of real data processing confirmed the applicability of this SAR tomograhic focusing method.},
    doi = {10.1109/LGRS.2011.2181321},
    
    }
    


  50. Yajing Yan, M.P. Doin, P. Lopez-Quiroz, F. Tupin, B. Fruneau, V. Pinel, and E. Trouve. Mexico City Subsidence Measured by InSAR Time Series: Joint Analysis Using PS and SBAS Approaches. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 5(4):1312-1326, August 2012. Keyword(s): AD 2002 11 to 2007 03, ENVISAT images, Gamma-IPTA chain, InSAR time series, Mexico City subsidence rate, adhoc SBAS approach, ground displacement rates, high-pass filtered difference maps, joint analysis method, low-pass filtered difference maps, multitemporal InSAR processing, permanent scatterer approach, small baseline subset approach, subsidence measurement method, subsidence pattern, subsoil compaction analysis, surface drying process, compaction, feature extraction, geophysical image processing, geophysical techniques, high-pass filters, low-pass filters, radar interferometry, soil, synthetic aperture radar, time series;.
    Abstract: In multi-temporal InSAR processing, both the Permanent Scatterer (PS) and Small BAseline Subset (SBAS) approaches are optimized to obtain ground displacement rates with a nominal accuracy of millimeters per year. In this paper, we investigate how applying both approaches to Mexico City subsidence validates the InSAR time series results and brings complementary information to the subsidence pattern. We apply the PS approach (Gamma-IPTA chain) and an ad-hoc SBAS approach on 38 ENVISAT images from November 2002 to March 2007 to map the Mexico City subsidence. The subsidence rate maps obtained by both approaches are compared quantitatively and analyzed at different steps of the PS processing. The inter-comparison is done separately for low-pass (LP) and high-pass (HP) filtered difference maps to take the complementarity of both approaches at different scales into account. The inter-comparison shows that the differential subsidence map obtained by the SBAS approach describes the local features associated with urban constructions and infrastructures, while the PS approach quantitatively characterizes the motion of individual targets. The latter information, once related to the type of building foundations, should be essential to quantify the relative importance of surface loads, surface drying and drying due to aquifer over-exploitation, in subsoil compaction.

    @Article{yanDoinLopeyQuiroyTupinFruneauPinelTrouve2012,
    Title = {Mexico City Subsidence Measured by {InSAR} Time Series: Joint Analysis Using {PS} and {SBAS} Approaches},
    Author = {Yajing Yan and Doin, M.P. and Lopez-Quiroz, P. and Tupin, F. and Fruneau, B. and Pinel, V. and Trouve, E.},
    Doi = {10.1109/JSTARS.2012.2191146},
    ISSN = {1939-1404},
    Month = aug,
    Number = {4},
    Pages = {1312-1326},
    Volume = {5},
    Year = {2012},
    Abstract = {In multi-temporal InSAR processing, both the Permanent Scatterer (PS) and Small BAseline Subset (SBAS) approaches are optimized to obtain ground displacement rates with a nominal accuracy of millimeters per year. In this paper, we investigate how applying both approaches to Mexico City subsidence validates the InSAR time series results and brings complementary information to the subsidence pattern. We apply the PS approach (Gamma-IPTA chain) and an ad-hoc SBAS approach on 38 ENVISAT images from November 2002 to March 2007 to map the Mexico City subsidence. The subsidence rate maps obtained by both approaches are compared quantitatively and analyzed at different steps of the PS processing. The inter-comparison is done separately for low-pass (LP) and high-pass (HP) filtered difference maps to take the complementarity of both approaches at different scales into account. The inter-comparison shows that the differential subsidence map obtained by the SBAS approach describes the local features associated with urban constructions and infrastructures, while the PS approach quantitatively characterizes the motion of individual targets. The latter information, once related to the type of building foundations, should be essential to quantify the relative importance of surface loads, surface drying and drying due to aquifer over-exploitation, in subsoil compaction.},
    Journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
    Keywords = {AD 2002 11 to 2007 03;ENVISAT images;Gamma-IPTA chain;InSAR time series;Mexico City subsidence rate;adhoc SBAS approach;ground displacement rates;high-pass filtered difference maps;joint analysis method;low-pass filtered difference maps;multitemporal InSAR processing;permanent scatterer approach;small baseline subset approach;subsidence measurement method;subsidence pattern;subsoil compaction analysis;surface drying process;compaction;feature extraction;geophysical image processing;geophysical techniques;high-pass filters;low-pass filters;radar interferometry;soil;synthetic aperture radar;time series;} 
    }
    


  51. L. Zhang, Z. Qiao, M. Xing, L. Yang, and Z. Bao. A Robust Motion Compensation Approach for UAV SAR Imagery. IEEE Trans. Geosci. Remote Sens., 50(8):3202-3218, August 2012. Keyword(s): autonomous aerial vehicles, geophysical image processing, geophysical techniques, maximum likelihood estimation, motion compensation, remote sensing by radar, synthetic aperture radar, robust motion compensation approach, UAV SAR imagery, unmanned aerial vehicle, synthetic aperture radar, remote sensing application, atmospheric turbulence, range invariant motion error, weighted phase gradient autofocus, nonsystematic range cell migration function, range dependent phase error, maximum likelihood WPGA algorithm, subaperture phase error, inertial navigation system, Electronics packaging, Estimation, Trajectory, Robustness, Navigation, Thyristors, Geometry, Local maximum-likelihood (LML), motion compensation (MOCO), phase gradient autofocus (PGA), synthetic aperture radar (SAR), unmanned aerial vehicle (UAV), weighted phase gradient autofocus (WPGA).
    Abstract: Unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) is an essential tool for modern remote sensing applications. Owing to its size and weight constraints, UAV is very sensitive to atmospheric turbulence that causes serious trajectory deviations. In this paper, a novel databased motion compensation (MOCO) approach is proposed for the UAV SAR imagery. The approach is implemented by a three-step process: 1) The range-invariant motion error is estimated by the weighted phase gradient autofocus (WPGA), and the nonsystematic range cell migration function is calculated from the estimate for each subaperture SAR data; 2) the retrieval of the range-dependent phase error is executed by a local maximum-likelihood WPGA algorithm; and 3) the subaperture phase errors are coherently combined to perform the MOCO for the full-aperture data. Both simulated and real-data experiments show that the proposed approach is appropriate for highly precise imaging for UAV SAR equipped with only low-accuracy inertial navigation system.

    @Article{zhangQiaoXingYangBaoTGRS2012RobustMoCompForUAVsarImagery,
    author = {L. {Zhang} and Z. {Qiao} and M. {Xing} and L. {Yang} and Z. {Bao}},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {A Robust Motion Compensation Approach for {UAV} {SAR} Imagery},
    year = {2012},
    issn = {1558-0644},
    month = aug,
    number = {8},
    pages = {3202-3218},
    volume = {50},
    abstract = {Unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) is an essential tool for modern remote sensing applications. Owing to its size and weight constraints, UAV is very sensitive to atmospheric turbulence that causes serious trajectory deviations. In this paper, a novel databased motion compensation (MOCO) approach is proposed for the UAV SAR imagery. The approach is implemented by a three-step process: 1) The range-invariant motion error is estimated by the weighted phase gradient autofocus (WPGA), and the nonsystematic range cell migration function is calculated from the estimate for each subaperture SAR data; 2) the retrieval of the range-dependent phase error is executed by a local maximum-likelihood WPGA algorithm; and 3) the subaperture phase errors are coherently combined to perform the MOCO for the full-aperture data. Both simulated and real-data experiments show that the proposed approach is appropriate for highly precise imaging for UAV SAR equipped with only low-accuracy inertial navigation system.},
    doi = {10.1109/TGRS.2011.2180392},
    keywords = {autonomous aerial vehicles;geophysical image processing;geophysical techniques;maximum likelihood estimation;motion compensation;remote sensing by radar;synthetic aperture radar;robust motion compensation approach;UAV SAR imagery;unmanned aerial vehicle;synthetic aperture radar;remote sensing application;atmospheric turbulence;range invariant motion error;weighted phase gradient autofocus;nonsystematic range cell migration function;range dependent phase error;maximum likelihood WPGA algorithm;subaperture phase error;inertial navigation system;Electronics packaging;Estimation;Trajectory;Robustness;Navigation;Thyristors;Geometry;Local maximum-likelihood (LML);motion compensation (MOCO);phase gradient autofocus (PGA);synthetic aperture radar (SAR);unmanned aerial vehicle (UAV);weighted phase gradient autofocus (WPGA)},
    owner = {ofrey},
    
    }
    


  52. Xiao Xiang Zhu and Richard Bamler. Demonstration of Super-Resolution for Tomographic SAR Imaging in Urban Environment. IEEE Trans. Geosci. Remote Sens., 50(8):3150-3157, August 2012. Keyword(s): SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry, InSAR, differential SAR interferometry, Persistent Scatterer Interferometry, PSI, DInSAR, Buildings, Image resolution, Optical imaging, Optical scattering, Signal resolution, Strontium, Tomography, geophysical equipment, geophysical image processing, radar imaging, SL1MMER algorithm, SR power, TerraSAR-X real data, classical linear estimators, differential SAR tomography, elevation aperture size, geometric analysis, meter-resolution spaceborne SAR systems, spectral analysis problem, statistical analysis, super-resolution demonstration, super-resolution reconstruction algorithms, super-resolving algorithm, synthetic aperture radar, tomographic SAR imaging, tomographic SAR inversion, tomographic elevation resolution, urban environment, urban infrastructure monitoring, Compressive sensing, SL1MMER, TerraSAR-X, sparse reconstruction, super-resolution, synthetic aperture radar, tomographic SAR inversion.
    Abstract: Tomographic synthetic aperture radar (SAR) inversion, including SAR tomography and differential SAR tomography, is essentially a spectral analysis problem. The resolution in the elevation direction depends on the elevation aperture size, i.e., on the spread of orbit tracks. Since the orbits of modern meter-resolution spaceborne SAR systems, such as TerraSAR-X, are tightly controlled, the tomographic elevation resolution is at least an order of magnitude lower than in range and azimuth. Hence, super-resolution (SR) reconstruction algorithms are desired. Considering the sparsity of the signal in elevation, a compressive sensing based super-resolving algorithm, named Scale-down by L1 norm Minimization, Model selection, and Estimation Reconstruction (SL1MMER, pronounced slimmer), was proposed by the authors in a previous paper. The ultimate bounds of the technique on localization accuracy and SR power were investigated. In this paper, the essential role of SR for layover separation in urban infrastructure monitoring is indicated by geometric and statistical analysis. It is shown that double scatterers with small elevation distances are more frequent than those with large elevation distances. Furthermore, the SR capability of SL1MMER is demonstrated using TerraSAR-X real data examples. For a high rise building complex, the percentage of detected double scatterers is almost doubled compared to classical linear estimators. Among them, half of the detected double scatterer pairs have elevation distances smaller than the Rayleigh elevation resolution. This confirms the importance of SR for this type of applications.

    @Article{zhuBamlerTGRS2012b,
    author = {Xiao Xiang Zhu and Bamler, Richard},
    title = {Demonstration of Super-Resolution for Tomographic {SAR} Imaging in Urban Environment},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2012},
    volume = {50},
    number = {8},
    pages = {3150-3157},
    month = aug,
    issn = {0196-2892},
    abstract = {Tomographic synthetic aperture radar (SAR) inversion, including SAR tomography and differential SAR tomography, is essentially a spectral analysis problem. The resolution in the elevation direction depends on the elevation aperture size, i.e., on the spread of orbit tracks. Since the orbits of modern meter-resolution spaceborne SAR systems, such as TerraSAR-X, are tightly controlled, the tomographic elevation resolution is at least an order of magnitude lower than in range and azimuth. Hence, super-resolution (SR) reconstruction algorithms are desired. Considering the sparsity of the signal in elevation, a compressive sensing based super-resolving algorithm, named Scale-down by L1 norm Minimization, Model selection, and Estimation Reconstruction (SL1MMER, pronounced slimmer), was proposed by the authors in a previous paper. The ultimate bounds of the technique on localization accuracy and SR power were investigated. In this paper, the essential role of SR for layover separation in urban infrastructure monitoring is indicated by geometric and statistical analysis. It is shown that double scatterers with small elevation distances are more frequent than those with large elevation distances. Furthermore, the SR capability of SL1MMER is demonstrated using TerraSAR-X real data examples. For a high rise building complex, the percentage of detected double scatterers is almost doubled compared to classical linear estimators. Among them, half of the detected double scatterer pairs have elevation distances smaller than the Rayleigh elevation resolution. This confirms the importance of SR for this type of applications.},
    doi = {10.1109/TGRS.2011.2177843},
    file = {:zhuBamlerTGRS2012b.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry, InSAR, differential SAR interferometry,Persistent Scatterer Interferometry, PSI, DInSAR,Buildings;Image resolution;Optical imaging;Optical scattering;Signal resolution;Strontium;Tomography;geophysical equipment; geophysical image processing;radar imaging; SL1MMER algorithm;SR power;TerraSAR-X real data;classical linear estimators;differential SAR tomography; elevation aperture size;geometric analysis;meter-resolution spaceborne SAR systems;spectral analysis problem;statistical analysis;super-resolution demonstration;super-resolution reconstruction algorithms; super-resolving algorithm;synthetic aperture radar;tomographic SAR imaging;tomographic SAR inversion;tomographic elevation resolution; urban environment;urban infrastructure monitoring;Compressive sensing;SL1MMER;TerraSAR-X;sparse reconstruction;super-resolution; synthetic aperture radar;tomographic SAR inversion},
    owner = {ofrey},
    pdf = {../../../docs/zhuBamlerTGRS2012b.pdf},
    
    }
    


  53. Xiao Xiang Zhu and Richard Bamler. Super-Resolution Power and Robustness of Compressive Sensing for Spectral Estimation With Application to Spaceborne Tomographic SAR. IEEE Trans. Geosci. Remote Sens., 50(1):247-258, January 2012. Keyword(s): SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry, Persistent Scatterer Interferometry, PSI, TerraSAR-X, X-band, Estimation, Image resolution, Minimization, Noise, Robustness, Strontium, Tomography, Fourier analysis, data acquisition, geophysical techniques, least squares approximations, maximum likelihood estimation, minimisation, probability, remote sensing by radar, spaceborne radar, synthetic aperture radar, tomography, Fourier domain sample, Rayleigh resolution analysis, SL1MMER algorithm, TomoSAR algorithm, compressive sensing robustness analysis, generic super-resolution problem, maximum likelihood parameter estimation, nonlinear least-squares estimation, numerical simulation, probability, spaceborne SAR tomography, sparse spectral estimation, spectral estimation method, super-resolution power, uniformly distributed phase difference analysis, Compressive sensing (CS), SAR tomography (TomoSAR), SL1MMER, spectral estimation, super-resolution (SR).
    Abstract: We address the problem of resolving two closely spaced complex-valued points from N irregular Fourier domain samples. Although this is a generic super-resolution (SR) problem, our target application is SAR tomography (TomoSAR), where typically the number of acquisitions is N = 10-100 and SNR = 0-10 dB. As the TomoSAR algorithm, we introduce Scale-down by L1 norm Minimization, Model selection, and Estimation Reconstruction (SL1MMER), which is a spectral estimation algorithm based on compressive sensing, model order selection, and final maximum likelihood parameter estimation. We investigate the limits of SLIMMER concerning the following questions. How accurately can the positions of two closely spaced scatterers be estimated? What is the closest distance of two scat- terers such that they can be separated with a detection rate of 50% by assuming a uniformly distributed phase difference? How many acquisitions N are required for a robust estimation (i.e., for separating two scatterers spaced by one Rayleigh resolution unit with a probability of 90%)? For all of these questions, we provide numerical results, simulations, and analytical approximations. Although we take TomoSAR as the preferred application, the SLIMMER algorithm and our results on SR are generally applicable to sparse spectral estimation, including SAR focusing of point-like objects. Our results are approximately applicable to nonlinear least-squares estimation, and hence, although it is derived experimentally, they can be considered as a fundamental bound for SR of spectral estimators. We show that SR factors are in the range of 1.5-25 for the aforementioned parameter ranges of N and SNR.

    @Article{zhuBamlerTGRS2012CS,
    author = {Xiao Xiang Zhu and Bamler, Richard},
    title = {Super-Resolution Power and Robustness of Compressive Sensing for Spectral Estimation With Application to Spaceborne Tomographic {SAR}},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2012},
    volume = {50},
    number = {1},
    pages = {247-258},
    month = jan,
    issn = {0196-2892},
    abstract = {We address the problem of resolving two closely spaced complex-valued points from N irregular Fourier domain samples. Although this is a generic super-resolution (SR) problem, our target application is SAR tomography (TomoSAR), where typically the number of acquisitions is N = 10-100 and SNR = 0-10 dB. As the TomoSAR algorithm, we introduce Scale-down by L1 norm Minimization, Model selection, and Estimation Reconstruction (SL1MMER), which is a spectral estimation algorithm based on compressive sensing, model order selection, and final maximum likelihood parameter estimation. We investigate the limits of SLIMMER concerning the following questions. How accurately can the positions of two closely spaced scatterers be estimated? What is the closest distance of two scat- terers such that they can be separated with a detection rate of 50% by assuming a uniformly distributed phase difference? How many acquisitions N are required for a robust estimation (i.e., for separating two scatterers spaced by one Rayleigh resolution unit with a probability of 90%)? For all of these questions, we provide numerical results, simulations, and analytical approximations. Although we take TomoSAR as the preferred application, the SLIMMER algorithm and our results on SR are generally applicable to sparse spectral estimation, including SAR focusing of point-like objects. Our results are approximately applicable to nonlinear least-squares estimation, and hence, although it is derived experimentally, they can be considered as a fundamental bound for SR of spectral estimators. We show that SR factors are in the range of 1.5-25 for the aforementioned parameter ranges of N and SNR.},
    doi = {10.1109/TGRS.2011.2160183},
    file = {:zhuBamlerTGRS2012CS.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry,Persistent Scatterer Interferometry, PSI, TerraSAR-X, X-band, Estimation;Image resolution;Minimization;Noise;Robustness;Strontium;Tomography;Fourier analysis;data acquisition;geophysical techniques;least squares approximations;maximum likelihood estimation;minimisation;probability;remote sensing by radar;spaceborne radar;synthetic aperture radar;tomography;Fourier domain sample;Rayleigh resolution analysis;SL1MMER algorithm;TomoSAR algorithm;compressive sensing robustness analysis;generic super-resolution problem;maximum likelihood parameter estimation;nonlinear least-squares estimation;numerical simulation;probability;spaceborne SAR tomography;sparse spectral estimation;spectral estimation method;super-resolution power;uniformly distributed phase difference analysis;Compressive sensing (CS);SAR tomography (TomoSAR);SL1MMER;spectral estimation;super-resolution (SR);synthetic aperture radar (SAR);},
    owner = {ofrey},
    pdf = {../../../docs/zhuBamlerTGRS2012CS.pdf},
    
    }
    


Conference articles

  1. Thomas M. Benson, Daniel P. Campbell, and Daniel A. Cook. Gigapixel spotlight synthetic aperture radar backprojection using clusters of GPUs and CUDA. In 2012 IEEE Radar Conference, pages 0853-0858, May 2012. Keyword(s): SAR Processing, Back-Projection, Time-Domain Back-Projection, TDBP, CUDA, GPU, SAR Focusing, Azimuth Focusing, fast Fourier transforms, graphics processing units, parallel architectures, radar computing, radar imaging, resource allocation, synthetic aperture radar, CUDA Clusters, GPU Clusters, SAR image formation, computing nodes, fast Fourier transforms, gigapixel scale data set, gigapixel spotlight synthetic aperture radar backprojection, graphics processing units, image formation algorithms, image formation framework, nonplanar surfaces, wavefront planarity, Graphics processing unit, History, Interpolation, Kernel, Scalability, Sparse matrices, Synthetic aperture radar.
    Abstract: Synthetic aperture radar (SAR) image formation via backprojection offers a robust mechanism by which to form images on general, non-planar surfaces, without often restrictive assumptions regarding the planarity of the wavefront at the locations being imaged. However, backprojection presents a substantially increased computational load relative to other image formation algorithms that typically depend upon fast Fourier transforms. In this paper, we present an image formation framework for accelerated SAR backprojection that utilizes a cluster of computing nodes, each with one or more graphics processing units (GPUs). We address the parallelization of the backprojection process among multiple nodes and the scalability thereby obtained, several optimization approaches, and performance as a function of both allocated resources and desired precision. Finally, we demonstrate the achieved performance on a simulated gigapixel-scale data set.

    @InProceedings{bensonCampbellCook2012GigaPixelNERFFTBackprojectionCUDA,
    author = {Benson, Thomas M. and Campbell, Daniel P. and Cook, Daniel A.},
    title = {Gigapixel spotlight synthetic aperture radar backprojection using clusters of {GPUs} and {CUDA}},
    booktitle = {2012 IEEE Radar Conference},
    year = {2012},
    pages = {0853-0858},
    month = may,
    abstract = {Synthetic aperture radar (SAR) image formation via backprojection offers a robust mechanism by which to form images on general, non-planar surfaces, without often restrictive assumptions regarding the planarity of the wavefront at the locations being imaged. However, backprojection presents a substantially increased computational load relative to other image formation algorithms that typically depend upon fast Fourier transforms. In this paper, we present an image formation framework for accelerated SAR backprojection that utilizes a cluster of computing nodes, each with one or more graphics processing units (GPUs). We address the parallelization of the backprojection process among multiple nodes and the scalability thereby obtained, several optimization approaches, and performance as a function of both allocated resources and desired precision. Finally, we demonstrate the achieved performance on a simulated gigapixel-scale data set.},
    doi = {10.1109/RADAR.2012.6212256},
    file = {:bensonCampbellCook2012GigaPixelNERFFTBackprojectionCUDA.pdf:PDF},
    issn = {1097-5659},
    keywords = {SAR Processing, Back-Projection, Time-Domain Back-Projection, TDBP, CUDA, GPU, SAR Focusing, Azimuth Focusing, fast Fourier transforms;graphics processing units;parallel architectures;radar computing;radar imaging;resource allocation;synthetic aperture radar;CUDA Clusters;GPU Clusters;SAR image formation;computing nodes;fast Fourier transforms;gigapixel scale data set;gigapixel spotlight synthetic aperture radar backprojection;graphics processing units;image formation algorithms;image formation framework;nonplanar surfaces;wavefront planarity;Graphics processing unit;History;Interpolation;Kernel;Scalability;Sparse matrices;Synthetic aperture radar},
    owner = {ofrey},
    pdf = {../../../docs/bensonCampbellCook2012GigaPixelNERFFTBackprojectionCUDA.pdf},
    
    }
    


  2. O.O. Bezvesilniy, I. M. Gorovyi, and D. M. Vavriv. Estimation of phase errors in SAR data by Local-Quadratic map-drift autofocus. In Proc. Int. Radar Symp., pages 376-381, 2012. Keyword(s): SAR Processing, Autofocus, SAR Autofocus, MoComp, Motion Compensation, Map-Drift Autofocus, airborne radar, radar imaging, synthetic aperture radar, SAR data, SAR images, X-band airborne SAR system, arbitrary residual phase error, local-quadratic map-drift autofocus, phase error estimation, quadratic errors, small data blocks, uncompensated phase errors, Antennas, Azimuth, Bandwidth, Doppler effect, Measurement uncertainty, Radar, Trajectory, autofocus, map-drift, motion compensation, motion errors, synthetic aperture radar.
    Abstract: Uncompensated phase errors lead to quality degradation of SAR images what is especially critical for high-resolution systems. In the paper, a novel approach to the stripmap autofocus is proposed. The idea of the method is to estimate the local quadratic phase errors by processing small data blocks. The conventional map-drift autofocus (MDA) algorithm is used for such estimation. Then, by a double integration of the estimated quadratic errors, an arbitrary residual phase error for large data blocks is evaluated. The performance of the proposed method is demonstrated with data obtained with an X-band airborne SAR system.

    @InProceedings{bezvesilniyGorovyiVavrivIRS2012Autofocus,
    author = {Bezvesilniy, O.O. and Gorovyi, I. M. and Vavriv, D. M.},
    title = {Estimation of phase errors in {SAR} data by Local-Quadratic map-drift autofocus},
    booktitle = {Proc. Int. Radar Symp.},
    year = {2012},
    pages = {376-381},
    abstract = {Uncompensated phase errors lead to quality degradation of SAR images what is especially critical for high-resolution systems. In the paper, a novel approach to the stripmap autofocus is proposed. The idea of the method is to estimate the local quadratic phase errors by processing small data blocks. The conventional map-drift autofocus (MDA) algorithm is used for such estimation. Then, by a double integration of the estimated quadratic errors, an arbitrary residual phase error for large data blocks is evaluated. The performance of the proposed method is demonstrated with data obtained with an X-band airborne SAR system.},
    doi = {10.1109/IRS.2012.6233350},
    file = {:bezvesilniyGorovyiVavrivIRS2012Autofocus.pdf:PDF},
    issn = {2155-5754},
    keywords = {SAR Processing, Autofocus, SAR Autofocus, MoComp, Motion Compensation, Map-Drift Autofocus,airborne radar;radar imaging;synthetic aperture radar;SAR data;SAR images;X-band airborne SAR system;arbitrary residual phase error;local-quadratic map-drift autofocus;phase error estimation;quadratic errors;small data blocks;uncompensated phase errors;Antennas;Azimuth;Bandwidth;Doppler effect;Measurement uncertainty;Radar;Trajectory;autofocus;map-drift;motion compensation;motion errors;synthetic aperture radar},
    pdf = {../../../docs/bezvesilniyGorovyiVavrivIRS2012Autofocus.pdf},
    
    }
    


  3. T. R. Clem, D. D. Sternlicht, J. E. Fernandez, J. L. Prater, R. Holtzapple, R. P. Gibson, J. P. Klose, and T. M. Marston. Demonstration of advanced sensors for underwater unexploded ordnance (UXO) detection. In Proc. Oceans, pages 1-4, October 2012. Keyword(s): inspection, oceanographic equipment, sensors, Office of Naval Research Small Synthetic Aperture MineHunter, REMUS BMI system, REMUS buried mine identification system, SSAM, UXO detection, UXO removal, advanced sensor demonstration, advanced sensors, clutter rejection, commercial-off-the-shelf sensors, diver inspections, hydronalix surfsense microUSV, hydronalix surfsense microunmanned surface vessel, man-made objects, military test ranges, seabed unexploded ordnance, subsurface UXO sized objects, underwater unexploded ordnance detection, Clutter, Inspection, Magnetic resonance imaging, Magnetoacoustic effects, Magnetometers, Sensors, Synthetic aperture sonar.
    @InProceedings{Clem2012,
    author = {T. R. Clem and D. D. Sternlicht and J. E. Fernandez and J. L. Prater and R. Holtzapple and R. P. Gibson and J. P. Klose and T. M. Marston},
    title = {Demonstration of advanced sensors for underwater unexploded ordnance (UXO) detection},
    booktitle = {Proc. Oceans},
    year = {2012},
    month = oct,
    pages = {1--4},
    doi = {10.1109/OCEANS.2012.6405131},
    issn = {0197-7385},
    keywords = {inspection, oceanographic equipment, sensors, Office of Naval Research Small Synthetic Aperture MineHunter, REMUS BMI system, REMUS buried mine identification system, SSAM, UXO detection, UXO removal, advanced sensor demonstration, advanced sensors, clutter rejection, commercial-off-the-shelf sensors, diver inspections, hydronalix surfsense microUSV, hydronalix surfsense microunmanned surface vessel, man-made objects, military test ranges, seabed unexploded ordnance, subsurface UXO sized objects, underwater unexploded ordnance detection, Clutter, Inspection, Magnetic resonance imaging, Magnetoacoustic effects, Magnetometers, Sensors, Synthetic aperture sonar},
    owner = {ofrey},
    
    }
    


  4. H. Essen, W. Johannes, S. Stanko, R. Sommer, A. Wahlen, and J. Wilcke. High resolution W-band UAV SAR. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 5033-5036, July 2012. Keyword(s): SAR Processing, W-Band, SUMATRA, Airborne SAR, UAV, Fraunhofer, geophysical equipment, remote sensing by radar, synthetic aperture radar, FM-CW principle, MIRANDA, SAR imaging, W-band UAV SAR, average transmit power, fibre optic gyroscope, frequency 94 GHz, high quality SAR processing, miniaturised millimetre wave radar, ordinary analogue data link, quick-look processing, real-time SAR-focusing algorithm, synthetic aperture radar, unmanned helicopter, Bandwidth, Chirp, Radar antennas, Real-time systems, Sensors, Synthetic aperture radar, High Resolution, Synthetic Aperture Radar, UAV, mm- waves.
    Abstract: A miniaturised millimetre wave radar, MIRANDA, to be used as Synthetic Aperture Radar onboard a small UAV was designed, built and tested onboard of an unmanned helicopter. The design followed the FM-CW principle, to get the highest possible average transmit power and thus the best range performance. The experiments described here were conducted at a centre frequency of 94 GHz. An inertial system of high quality, based upon a fibre optic gyroscope maintained the necessary precision, to allow high resolution SAR imaging. The raw data are transmitted to the ground station using an ordinary analogue data link, where they are A/D converted, preprocessed and finally undergo a real-time SAR-focusing algorithm. Additionally to the quick-look processing the data are stored to be able to apply further high quality SAR processing. The paper describes the design principles and gives results from the flight tests.

    @InProceedings{EssenEtAlIAGRSS2012wbandSUMATRASARforUAV,
    author = {H. Essen and W. Johannes and S. Stanko and R. Sommer and A. Wahlen and J. Wilcke},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    title = {High resolution {W}-band {UAV} {SAR}},
    year = {2012},
    month = jul,
    pages = {5033-5036},
    abstract = {A miniaturised millimetre wave radar, MIRANDA, to be used as Synthetic Aperture Radar onboard a small UAV was designed, built and tested onboard of an unmanned helicopter. The design followed the FM-CW principle, to get the highest possible average transmit power and thus the best range performance. The experiments described here were conducted at a centre frequency of 94 GHz. An inertial system of high quality, based upon a fibre optic gyroscope maintained the necessary precision, to allow high resolution SAR imaging. The raw data are transmitted to the ground station using an ordinary analogue data link, where they are A/D converted, preprocessed and finally undergo a real-time SAR-focusing algorithm. Additionally to the quick-look processing the data are stored to be able to apply further high quality SAR processing. The paper describes the design principles and gives results from the flight tests.},
    doi = {10.1109/IGARSS.2012.6352480},
    issn = {2153-6996},
    keywords = {SAR Processing, W-Band,SUMATRA, Airborne SAR, UAV, Fraunhofer,geophysical equipment;remote sensing by radar;synthetic aperture radar;FM-CW principle;MIRANDA;SAR imaging;W-band UAV SAR;average transmit power;fibre optic gyroscope;frequency 94 GHz;high quality SAR processing;miniaturised millimetre wave radar;ordinary analogue data link;quick-look processing;real-time SAR-focusing algorithm;synthetic aperture radar;unmanned helicopter;Bandwidth;Chirp;Radar antennas;Real-time systems;Sensors;Synthetic aperture radar;High Resolution;Synthetic Aperture Radar;UAV;mm- waves},
    owner = {ofrey},
    
    }
    


  5. Othmar Frey, Erich Meier, and Irena Hajnsek. Towards a more reliable estimation of forest parameters from polarimetric SAR tomography data. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 3110-3113, 2012. Keyword(s): Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, synthetic aperture radar, SAR, scattering, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation.
    Abstract: n this contribution, tomographic imagery obtained from estimating the 3-D localization and the polarimetric signature of backscattering sources within a forest environment from fully-polarimetric multibaseline SAR data at L- and P-bands are presented. Both, polarization diversity and spatial diversity were exploited jointly within the tomographic focusing to estimate the targets' localization and polarimetric signature. We thereby ex- tend our recently proposed time-domain back-projection (TDBP)-based tomographic focusing approach. The tomo- graphic slices obtained from polarimetric spectral estima- tion using MLBF, Capon, and MUSIC are opposed to the results previously obtained by tomographic focusing of the individual polarization channels. The results are briefly discussed with respect to potential advancements towards more reliable estimation of forest parameters from SAR tomography data.

    @InProceedings{freyMeierHajnsekIGARSS2012Tomo,
    author = {Othmar Frey and Erich Meier and Irena Hajnsek},
    title = {Towards a more reliable estimation of forest parameters from polarimetric SAR tomography data},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2012},
    pages = {3110-3113},
    abstract = {n this contribution, tomographic imagery obtained from estimating the 3-D localization and the polarimetric signature of backscattering sources within a forest environment from fully-polarimetric multibaseline SAR data at L- and P-bands are presented. Both, polarization diversity and spatial diversity were exploited jointly within the tomographic focusing to estimate the targets' localization and polarimetric signature. We thereby ex- tend our recently proposed time-domain back-projection (TDBP)-based tomographic focusing approach. The tomo- graphic slices obtained from polarimetric spectral estima- tion using MLBF, Capon, and MUSIC are opposed to the results previously obtained by tomographic focusing of the individual polarization channels. The results are briefly discussed with respect to potential advancements towards more reliable estimation of forest parameters from SAR tomography data.},
    file = {:freyMeierHajnsekIGARSS2012Tomo.pdf:PDF},
    keywords = {Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, synthetic aperture radar, SAR, scattering, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation},
    owner = {ofrey},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyMeierHajnsekIGARSS2012Tomo.pdf},
    
    }
    


  6. Othmar Frey, Erich Meier, and Irena Hajnsek. Tweaking baseline constellations for airborne SAR tomography and InSAR: an experimental study at L- and P-bands. In Proc. EUSAR 2012 - 9th European Conference on Synthetic Aperture Radar, pages 215-218, 2012. Keyword(s): Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, synthetic aperture radar, SAR, scattering, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation.
    Abstract: A notable obstacle hindering widespread application of SAR tomography for 3D mapping of vegetation is the relatively large number of acquisitions that are needed to obtain a high resolution and a good rejection of spurious responses in the direction perpendicular to the line of sight. In this paper, we discuss the impact of different baseline constellations on 3-D mapping of vegetation volumes and the underlying topography in terms of tomographic focusing as well as classical single-baseline repeat-pass interferometry. The effects are studied using two airborne tomography data sets at L- and P-bands.

    @InProceedings{freyMeierHajnsekEUSAR2012Tomo,
    author = {Othmar Frey and Erich Meier and Irena Hajnsek},
    title = {Tweaking baseline constellations for airborne {SAR} tomography and {InSAR}: an experimental study at {L-} and {P-bands}},
    booktitle = {Proc. EUSAR 2012 - 9th European Conference on Synthetic Aperture Radar},
    year = {2012},
    pages = {215-218},
    abstract = {A notable obstacle hindering widespread application of SAR tomography for 3D mapping of vegetation is the relatively large number of acquisitions that are needed to obtain a high resolution and a good rejection of spurious responses in the direction perpendicular to the line of sight. In this paper, we discuss the impact of different baseline constellations on 3-D mapping of vegetation volumes and the underlying topography in terms of tomographic focusing as well as classical single-baseline repeat-pass interferometry. The effects are studied using two airborne tomography data sets at L- and P-bands.},
    file = {:freyMeierHajnsekEUSAR2012Tomo.pdf:PDF},
    keywords = {Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, synthetic aperture radar, SAR, scattering, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation},
    owner = {ofrey},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyMeierHajnsekEUSAR2012.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6217025},
    
    }
    


  7. Othmar Frey, Urs Wegmuller, and Charles L. Werner. Terrain motion measurements over European urban areas using persistent scatterer interferometry. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 7565-7568, 2012. Keyword(s): Spaceborne radar, Persistent Scatterer Interferometry, PSI, PanGeo, C-Band, Terrain motion, subsidence, interferometry, InSAR, SAR Interferometry, Remote Sensing, synthetic aperture radar, SAR, scattering, Urban Areas.
    Abstract: In this contribution Persistent Scatterer Interferometry (PSI) processings done in the framework of the FP7 Project PanGEO over a number of European sites are presented. After a short introduction of the PanGEO project, we present the data used, the processing done and the results of the PSI analysis. The influence of specifics as the presence of large non-urban areas, significant topography, seasonal effects, special deformation characteristics, and the size of the available data stacks on the processing are highlighted.

    @InProceedings{freyWegmullerWernerIGARSS2012PanGeo,
    author = {Othmar Frey and Urs Wegmuller and Charles L. Werner},
    title = {Terrain motion measurements over {E}uropean urban areas using persistent scatterer interferometry},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2012},
    pages = {7565-7568},
    abstract = {In this contribution Persistent Scatterer Interferometry (PSI) processings done in the framework of the FP7 Project PanGEO over a number of European sites are presented. After a short introduction of the PanGEO project, we present the data used, the processing done and the results of the PSI analysis. The influence of specifics as the presence of large non-urban areas, significant topography, seasonal effects, special deformation characteristics, and the size of the available data stacks on the processing are highlighted.},
    doi = {10.1109/IGARSS.2012.6351911},
    file = {:freyWegmullerWernerIGARSS2012PanGeo.pdf:PDF},
    keywords = {Spaceborne radar, Persistent Scatterer Interferometry, PSI, PanGeo, C-Band, Terrain motion, subsidence, interferometry, InSAR, SAR Interferometry, Remote Sensing, synthetic aperture radar, SAR, scattering, Urban Areas},
    owner = {ofrey},
    url = {https://ieeexplore.ieee.org/document/6351911},
    
    }
    


  8. Luca Marotti, Pau Prats, Rolf Scheiber, Steffen Wollstadt, and Andreas Reigber. Differential SAR interferometry with TerraSAR-X TOPS data: Mexico city subsidence results. In Synthetic Aperture Radar, 2012. EUSAR. 9th European Conference on, pages 677-680, April 2012. Keyword(s): SAR Processing, TOPS, Terrain Observation by Progressive Scans, Azimuth, Decorrelation, Estimation, Interferometry, Signal resolution, Synthetic aperture radar, Time frequency analysis.
    Abstract: In this paper we investigate the possibility to exploit TOPS (Terrain Observation by Progressive Scan) data to measure ground displacement movements by means of Differential SAR Interferometry (DInSAR). Several critical points (i.e. coregistration) have to be faced during the data processing since, due to the TOPS signal characteristics, the interferometric chain is very sensitive to small implementation errors. The obtained results will be compared with the ones conventionally retrieved when applying DInSAR on stripmap data. Finally, the potential of DInSAR measurements, when combining TOPS and stripmap data by means of point-like scatterers, will be also analysed.

    @InProceedings{marottiPratsScheiberWollstadtReigberEUSAR2012TOPSINSAR,
    author = {Marotti, Luca and Prats, Pau and Scheiber, Rolf and Wollstadt, Steffen and Reigber, Andreas},
    title = {Differential SAR interferometry with TerraSAR-X TOPS data: Mexico city subsidence results},
    booktitle = {Synthetic Aperture Radar, 2012. EUSAR. 9th European Conference on},
    year = {2012},
    pages = {677-680},
    month = {April},
    abstract = {In this paper we investigate the possibility to exploit TOPS (Terrain Observation by Progressive Scan) data to measure ground displacement movements by means of Differential SAR Interferometry (DInSAR). Several critical points (i.e. coregistration) have to be faced during the data processing since, due to the TOPS signal characteristics, the interferometric chain is very sensitive to small implementation errors. The obtained results will be compared with the ones conventionally retrieved when applying DInSAR on stripmap data. Finally, the potential of DInSAR measurements, when combining TOPS and stripmap data by means of point-like scatterers, will be also analysed.},
    file = {:marottiPratsScheiberWollstadtReigberEUSAR2012TOPSINSAR.pdf:PDF},
    keywords = {SAR Processing, TOPS, Terrain Observation by Progressive Scans,Azimuth;Decorrelation;Estimation;Interferometry;Signal resolution;Synthetic aperture radar;Time frequency analysis},
    pdf = {../../../docs/marottiPratsScheiberWollstadtReigberEUSAR2012TOPSINSAR.pdf},
    
    }
    


  9. T. Marston. A correlation-based autofocus algorithm for coherent circular synthetic aperture sonar. In Proc. EUSAR 2012; 9th European Conf. Synthetic Aperture Radar, pages 66-69, April 2012. Keyword(s): Apertures, Correlation, Fourier transforms, Manganese, Navigation, Synthetic aperture sonar.
    @InProceedings{Marston2012,
    author = {T. Marston},
    title = {A correlation-based autofocus algorithm for coherent circular synthetic aperture sonar},
    booktitle = {Proc. EUSAR 2012; 9th European Conf. Synthetic Aperture Radar},
    year = {2012},
    month = apr,
    pages = {66--69},
    keywords = {Apertures, Correlation, Fourier transforms, Manganese, Navigation, Synthetic aperture sonar},
    owner = {ofrey},
    
    }
    


  10. D. Monells, R. Iglesias, Jordi J. Mallorqui, X. Fabregas, and C. Lopez-Martinez. Phase quality optimization in Orbital Differential SAR Interferometry with fully polarimetric data. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 1864-1867, 2012. Keyword(s): SAR Processing, PSI, Persistent Scatterer Interferometry, Spaceborne SAR, InSAR, DInSAR, Polarimetry, geophysical image processing, geophysical techniques, optimisation, radar interferometry, radar polarimetry, synthetic aperture radar, Barcelona, DInSAR processing, Fine Quad-Pol Radarsat-2 acquisitions, Radarsat-2, Spain, TerraSAR-X, analytical techniques, fully polarimetric data, interferometric technique, orbital Differential SAR Interferometry, phase quality optimization, polarimetric technique, single polarization SAR, terrain deformation phenomena, Coherence, Correlation, Histograms, Interferometry, Optimization, Synthetic aperture radar, Vectors, Coherence optimization, Pol-DInSAR, Terrain deformation, multi-baseline.
    Abstract: Orbital Differential SAR Interferometry (DInSAR) is a well-known technique to retrieve terrain deformation phenomena from wide areas with high resolution. Historically its application has been limited to single polarization SAR, mainly due to the unavailability of polarimetric data. Lately, the launch of several satellites with polarimetric capabilities, such as Radarsat-2 or TerraSAR-X, allows merging polarimetric and interferometric techniques in order to improve the results obtained in the DInSAR processing. This work will explore the existent analytical techniques in order to optimize the quality of the subsidence results. The dataset used contains 35 Fine Quad-Pol Radarsat-2 acquisitions over the city of Barcelona (Spain).

    @InProceedings{monellsIglesiasMallorquiFabregasLopezMartinez2012DINSARPolarimetric,
    author = {Monells, D. and Iglesias, R. and Mallorqui, Jordi J. and Fabregas, X. and Lopez-Martinez, C.},
    title = {Phase quality optimization in Orbital Differential {SAR} Interferometry with fully polarimetric data},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2012},
    pages = {1864-1867},
    abstract = {Orbital Differential SAR Interferometry (DInSAR) is a well-known technique to retrieve terrain deformation phenomena from wide areas with high resolution. Historically its application has been limited to single polarization SAR, mainly due to the unavailability of polarimetric data. Lately, the launch of several satellites with polarimetric capabilities, such as Radarsat-2 or TerraSAR-X, allows merging polarimetric and interferometric techniques in order to improve the results obtained in the DInSAR processing. This work will explore the existent analytical techniques in order to optimize the quality of the subsidence results. The dataset used contains 35 Fine Quad-Pol Radarsat-2 acquisitions over the city of Barcelona (Spain).},
    doi = {10.1109/IGARSS.2012.6351143},
    file = {:monellsIglesiasMallorquiFabregasLopezMartinez2012DINSARPolarimetric.pdf:PDF},
    issn = {2153-6996},
    keywords = {SAR Processing, PSI, Persistent Scatterer Interferometry, Spaceborne SAR, InSAR, DInSAR, Polarimetry, geophysical image processing;geophysical techniques;optimisation;radar interferometry;radar polarimetry;synthetic aperture radar;Barcelona;DInSAR processing;Fine Quad-Pol Radarsat-2 acquisitions;Radarsat-2;Spain;TerraSAR-X;analytical techniques;fully polarimetric data;interferometric technique;orbital Differential SAR Interferometry;phase quality optimization;polarimetric technique;single polarization SAR;terrain deformation phenomena;Coherence;Correlation;Histograms;Interferometry;Optimization;Synthetic aperture radar;Vectors;Coherence optimization;Pol-DInSAR;Terrain deformation;multi-baseline},
    owner = {ofrey},
    pdf = {../../../docs/monellsIglesiasMallorquiFabregasLopezMartinez2012DINSARPolarimetric.pdf},
    
    }
    


  11. O. Ponce, P. Prats, R. Scheiber, A. Reigber, and A. Moreira. Multibaseline 3-D circular SAR imaging at L-band. In Proc. EUSAR 2012; 9th European Conf. Synthetic Aperture Radar, pages 113-116, April 2012. Keyword(s): Apertures, Image reconstruction, Image resolution, Imaging, L-band, Synthetic aperture radar, Three dimensional displays.
    @InProceedings{Ponce2012a,
    author = {O. Ponce and P. Prats and R. Scheiber and A. Reigber and A. Moreira},
    title = {Multibaseline {3-D} circular {SAR} imaging at L-band},
    booktitle = {Proc. EUSAR 2012; 9th European Conf. Synthetic Aperture Radar},
    year = {2012},
    month = apr,
    pages = {113--116},
    keywords = {Apertures, Image reconstruction, Image resolution, Imaging, L-band, Synthetic aperture radar, Three dimensional displays},
    owner = {ofrey},
    
    }
    


  12. O. Ponce, P. Prats, R. Scheiber, A. Reigber, and A. Moreira. Polarimetric 3-D reconstruction from multicircular SAR at P-band. In Proc. IEEE Int. Geoscience and Remote Sensing Symp, pages 3130-3133, July 2012. Keyword(s): array signal processing, calibration, image reconstruction, image resolution, radar imaging, radar polarimetry, singular value decomposition, synthetic aperture radar, 3D imaging, CSAR mode, DLR F-SAR system, SVD, backscattering profile, beamforming, compressive sensing, cone-shaped sidelobes, fast factorized back projection, holographic SAR tomogram, multicircular fully polarimetric SAR experiment, phase calibration method, polarimetric 3D reconstruction, polarimetric three-dimensional reconstruction, singular value decomposition, subwavelength resolution, Array signal processing, Calibration, Focusing, Image reconstruction, Image resolution, Synthetic aperture radar, Tomography, Circular SAR, PolSAR, compressive sensing, holographic tomography, multicircular SAR.
    @InProceedings{Ponce2012,
    author = {O. Ponce and P. Prats and R. Scheiber and A. Reigber and A. Moreira},
    title = {Polarimetric {3-D} reconstruction from multicircular {SAR} at P-band},
    booktitle = {Proc. IEEE Int. Geoscience and Remote Sensing Symp},
    year = {2012},
    month = jul,
    pages = {3130--3133},
    doi = {10.1109/IGARSS.2012.6350762},
    issn = {2153-6996},
    keywords = {array signal processing, calibration, image reconstruction, image resolution, radar imaging, radar polarimetry, singular value decomposition, synthetic aperture radar, 3D imaging, CSAR mode, DLR F-SAR system, SVD, backscattering profile, beamforming, compressive sensing, cone-shaped sidelobes, fast factorized back projection, holographic SAR tomogram, multicircular fully polarimetric SAR experiment, phase calibration method, polarimetric 3D reconstruction, polarimetric three-dimensional reconstruction, singular value decomposition, subwavelength resolution, Array signal processing, Calibration, Focusing, Image reconstruction, Image resolution, Synthetic aperture radar, Tomography, Circular SAR, PolSAR, compressive sensing, holographic tomography, multicircular SAR},
    owner = {ofrey},
    
    }
    


  13. M. A. Remy, Karlus A. Camara de Macedo, and Joao R. Moreira. The first UAV-based P- and X-band interferometric SAR system. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 5041-5044, July 2012. Keyword(s): geophysical equipment, radar interferometry, remote sensing, synthetic aperture radar, UAV-based P-band interferometric SAR system, UAV-based X-band interferometric SAR system, OrbiSat system, Brazil, compact InSAR system, flexible InSAR system, topographic survey, differential interferometry, unmanned air vehicle, Synthetic aperture radar, Global Positioning System, Remote sensing, Interferometry, Radar antennas, UAV, SAR, P, X, interferometry.
    Abstract: In this paper we present the design overview of the UAV-based P- (repeat-pass) and X-band (single-pass) interferometric SAR system of OrbiSat, Brazil. The main objective is to built a compact and flexible InSAR system capable of performing accurate topographic survey and differential interferometry. To our knowledge, this is the first UAV-based In-SAR system with such characteristics, multi-band and fixed-baseline (X-band), to be projected. The status, and some main project results and solution are described and depicted.

    @InProceedings{remyDeMacedoMoreiraIGARSS2012FirstUAVbasedPandXbandSARSystem,
    author = {M. A. {Remy} and Camara de Macedo, Karlus A. and Moreira, Joao R.},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    title = {The first {UAV}-based {P-} and {X-}band interferometric {SAR} system},
    year = {2012},
    month = {July},
    pages = {5041-5044},
    abstract = {In this paper we present the design overview of the UAV-based P- (repeat-pass) and X-band (single-pass) interferometric SAR system of OrbiSat, Brazil. The main objective is to built a compact and flexible InSAR system capable of performing accurate topographic survey and differential interferometry. To our knowledge, this is the first UAV-based In-SAR system with such characteristics, multi-band and fixed-baseline (X-band), to be projected. The status, and some main project results and solution are described and depicted.},
    doi = {10.1109/IGARSS.2012.6352478},
    issn = {2153-7003},
    keywords = {geophysical equipment;radar interferometry;remote sensing;synthetic aperture radar;UAV-based P-band interferometric SAR system;UAV-based X-band interferometric SAR system;OrbiSat system;Brazil;compact InSAR system;flexible InSAR system;topographic survey;differential interferometry;unmanned air vehicle;Synthetic aperture radar;Global Positioning System;Remote sensing;Interferometry;Radar antennas;UAV;SAR;P;X;interferometry},
    
    }
    


  14. Angel Ribalta. Optimizing the factorisation parameters in the fast factorized backprojection algorithm. In Proc. EUSAR 2012 - 9th European Conference on Synthetic Aperture Radar, pages 356-359, April 2012. Keyword(s): SAR Processing, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, Optimization, Factorization Parameter Optimization.
    Abstract: An explicit formula for optimizing the factorisation parameters in the fast factorized backprojection algorithm is given. It is shown that the optimal factorisation basis is given by b = 3, whereas the optimal number of factorisation levels can be easily computed a priori. A numerical example illustrates the effectivity of the proposed choice.

    @InProceedings{ribaltaFFBPeusar2012,
    author = {Angel Ribalta},
    title = {Optimizing the factorisation parameters in the fast factorized backprojection algorithm},
    booktitle = {Proc. EUSAR 2012 - 9th European Conference on Synthetic Aperture Radar},
    year = {2012},
    pages = {356-359},
    month = apr,
    abstract = {An explicit formula for optimizing the factorisation parameters in the fast factorized backprojection algorithm is given. It is shown that the optimal factorisation basis is given by b = 3, whereas the optimal number of factorisation levels can be easily computed a priori. A numerical example illustrates the effectivity of the proposed choice.},
    file = {:ribaltaFFBPeusar2012.pdf:PDF},
    keywords = {SAR Processing, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, Optimization, Factorization Parameter Optimization},
    pdf = {../../../docs/ribaltaFFBPeusar2012.pdf},
    
    }
    


  15. S. Rdelsperger, A. Coccia, D. Vicente, and A. Meta. Introduction to the new metasensing ground-based SAR: Technical description and data analysis. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 4790-4792, July 2012. Keyword(s): data analysis, geophysical equipment, geophysical image processing, synthetic aperture radar, metasensing ground-based SAR, data analysis, MetaSensing FastGBSAR, high sampling rate, submillimeter accuracy, Synthetic aperture radar, Sensors, Monitoring, Instruments, Microwave imaging, Microwave theory and techniques, Accuracy.
    Abstract: This paper introduced the novel MetaSensing FastGBSAR with the ability to map deformations of a large area in real-time with a high sampling rate of less then 10 seconds per image. Therefore, the sensor allows the reliable measurement of deformations with sub-millimeter accuracy in a variety of applications. The first campaign with a prototype is currently in progress. The analysis and results will be shown at the conference.

    @InProceedings{roedelspergerCocciaVicenteMetaIGARSS2010FastGBSAR,
    author = {S. {R\"odelsperger} and A. {Coccia} and D. {Vicente} and A. {Meta}},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    title = {Introduction to the new metasensing ground-based {SAR}: Technical description and data analysis},
    year = {2012},
    month = {July},
    pages = {4790-4792},
    abstract = {This paper introduced the novel MetaSensing FastGBSAR with the ability to map deformations of a large area in real-time with a high sampling rate of less then 10 seconds per image. Therefore, the sensor allows the reliable measurement of deformations with sub-millimeter accuracy in a variety of applications. The first campaign with a prototype is currently in progress. The analysis and results will be shown at the conference.},
    doi = {10.1109/IGARSS.2012.6352542},
    issn = {2153-7003},
    keywords = {data analysis;geophysical equipment;geophysical image processing;synthetic aperture radar;metasensing ground-based SAR;data analysis;MetaSensing FastGBSAR;high sampling rate;submillimeter accuracy;Synthetic aperture radar;Sensors;Monitoring;Instruments;Microwave imaging;Microwave theory and techniques;Accuracy},
    owner = {ofrey},
    
    }
    


  16. Urs Wegmuller, Othmar Frey, and Charles L. Werner. Point Density Reduction in Persistent Scatterer Interferometry. In Proc. EUSAR 2012 - 9th European Conference on Synthetic Aperture Radar, pages 673-676, 2012. Keyword(s): SAR processing, PSI, Persistent Scatterer Interferometry, interferometry, InSAR, multibaseline InSAR, point density, point density reduction.
    Abstract: Persistent Scatterer Interferometry (PSI) is widely used to determine ground deformation rates and histories. The data sets processed are increasing in size due to larger areas considered, higher resolution, and higher point den- sities. Working with lists of several million points and related networks reduces the computational efficiency. In this paper a method to adaptively reduce the size of the point list is presented. Considering the local point density and a point quality measure points are removed such that the density is significantly reduced in areas of very high density while maintaining the available density in areas of lower density. The main PSI processing is then done for the reduced point list. Later on the result obtained for the reduced list is expanded to the full point list. In sev- eral cases this methodology improves the processing efficiency significantly.

    @InProceedings{wegmullerFreyWernerEUSAR2012PointDensity,
    author = {Urs Wegmuller and Othmar Frey and Charles L. Werner},
    title = {Point Density Reduction in Persistent Scatterer Interferometry},
    booktitle = {Proc. EUSAR 2012 - 9th European Conference on Synthetic Aperture Radar},
    year = {2012},
    pages = {673-676},
    abstract = {Persistent Scatterer Interferometry (PSI) is widely used to determine ground deformation rates and histories. The data sets processed are increasing in size due to larger areas considered, higher resolution, and higher point den- sities. Working with lists of several million points and related networks reduces the computational efficiency. In this paper a method to adaptively reduce the size of the point list is presented. Considering the local point density and a point quality measure points are removed such that the density is significantly reduced in areas of very high density while maintaining the available density in areas of lower density. The main PSI processing is then done for the reduced point list. Later on the result obtained for the reduced list is expanded to the full point list. In sev- eral cases this methodology improves the processing efficiency significantly.},
    file = {:wegmullerFreyWernerEUSAR2012PointDensity.pdf:PDF},
    keywords = {SAR processing, PSI, Persistent Scatterer Interferometry, interferometry, InSAR, multibaseline InSAR, point density, point density reduction},
    owner = {ofrey},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6217159},
    
    }
    


  17. Urs Wegmuller, Tazio Strozzi, and Charles Werner. Ionospheric path delay estimation using split-beam interferometry. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 3631-3634, July 2012. Keyword(s): SAR Processing, Ionosphere, Ionospheric Path Delay, split-beam interferometry, SBI, ionospheric electromagnetic wave propagation, ionospheric techniques, radar interferometry, remote sensing by radar, L-band split beam interferograms, along track ground displacement estimation, azimuth spectrum band pass filtering, directional scattering identification, ionospheric path delay estimation, long baseline pair coherence estimation, split beam interferometry, Azimuth, Band pass filters, Coherence, Delay, Ionosphere, L-band, Time series analysis, Split-beam interferometry, ionosphere, ionospheric path delay.
    Abstract: Azimuth spectrum band-pass filtering has been applied successfully for estimation of along-track ground displacement [1] as well as for other applications, such as the identification of directional scattering [2] and the coherence estimation for long-baseline pairs [3]. Particularly L-band split-beam interferograms have shown another phase component related to along-track variations in the ionospheric path delay. In our work we present methodologies to identify and quantify ionospheric path delays affecting an interferogram using the corresponding split-beam interferogram.

    @InProceedings{wegmullerStrozziWernerIGARSS2012SplitBeamInterferometryIonosphericPathDelay,
    author = {Urs Wegmuller and Tazio Strozzi and Charles Werner},
    title = {Ionospheric path delay estimation using split-beam interferometry},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2012},
    pages = {3631-3634},
    month = jul,
    abstract = {Azimuth spectrum band-pass filtering has been applied successfully for estimation of along-track ground displacement [1] as well as for other applications, such as the identification of directional scattering [2] and the coherence estimation for long-baseline pairs [3]. Particularly L-band split-beam interferograms have shown another phase component related to along-track variations in the ionospheric path delay. In our work we present methodologies to identify and quantify ionospheric path delays affecting an interferogram using the corresponding split-beam interferogram.},
    doi = {10.1109/IGARSS.2012.6350630},
    file = {:wegmullerStrozziWernerIGARSS2012SplitBeamInterferometryIonosphericPathDelay.pdf:PDF},
    issn = {2153-6996},
    keywords = {SAR Processing, Ionosphere, Ionospheric Path Delay, split-beam interferometry, SBI, ionospheric electromagnetic wave propagation;ionospheric techniques;radar interferometry;remote sensing by radar;L-band split beam interferograms;along track ground displacement estimation;azimuth spectrum band pass filtering;directional scattering identification;ionospheric path delay estimation;long baseline pair coherence estimation;split beam interferometry;Azimuth;Band pass filters;Coherence;Delay;Ionosphere;L-band;Time series analysis;Split-beam interferometry;ionosphere;ionospheric path delay},
    owner = {ofrey},
    
    }
    


  18. Charles L. Werner, Andreas Wiesmann, Tazio Strozzi, Andrew Kos, Rafael Caduff, and Urs Wegmuller. The GPRI multi-mode differential interferometric radar for ground-based observations. In Proc. EUSAR 2012, pages 304-307, April 2012. Keyword(s): SAR Processing, Interferometry, Radar, Radar interferometry, Surface deformation;.
    Abstract: We describe the Gamma Portable Radar Interferometer (GPRI), an instrument designed to perform ground-based radar interferometry to measure surface deformation with an accuracy < 0.2 mm and generate digital elevation models (DEMs). Ground-based interferometric observations are complementary to spaceborne or airborne SAR based measurements because they can be acquired continuously in order to track rapid deformation and mitigate the effects of temporal decorrelation and atmospheric phase variability. Results from test cases are shown including the Aletsch glacier, Aletschwald, and Kornhaus bridge in Bern.

    @InProceedings{wernerWiesmannStrozziKosCaduffWegmullerEUSAR2012GPRI2,
    author = {Werner, Charles L. and Wiesmann, Andreas and Strozzi, Tazio and Kos, Andrew and Caduff, Rafael and Wegmuller, Urs},
    title = {The {GPRI} multi-mode differential interferometric radar for ground-based observations},
    booktitle = {Proc. EUSAR 2012},
    year = {2012},
    pages = {304-307},
    month = apr,
    abstract = {We describe the Gamma Portable Radar Interferometer (GPRI), an instrument designed to perform ground-based radar interferometry to measure surface deformation with an accuracy < 0.2 mm and generate digital elevation models (DEMs). Ground-based interferometric observations are complementary to spaceborne or airborne SAR based measurements because they can be acquired continuously in order to track rapid deformation and mitigate the effects of temporal decorrelation and atmospheric phase variability. Results from test cases are shown including the Aletsch glacier, Aletschwald, and Kornhaus bridge in Bern.},
    keywords = {SAR Processing, Interferometry;Radar;Radar interferometry;Surface deformation;},
    owner = {ofrey},
    pdf = {../../../docs/wernerWiesmannStrozziKosCaduffWegmullerEUSAR2012GPRI2.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6217065},
    
    }
    


Internal reports

  1. Shaun Quegan, Thuy Le Toan, Jrme Chave, Jorgen Dall, Konstantinos P. Papathanassiou, Fabio Rocca, Lars Ulander, and Mathew Williams. Report for Mission Selection: Biomass. Technical report SP-1324/1 (3 volume series), ESA, Noordwijk, The Netherlands, May 2012. Keyword(s): BIOMASS, BIOMASS MISSION, ESA, European Space Agency, P-Band, Spaceborne SAR, SAR.
    Abstract: The Earth Explorer Biomass mission will provide the scientific community with the first accurate maps of tropical, temperate and boreal forest biomass, including height and disturbance patterns. This information is urgently needed to improve our understanding of the global carbon cycle and to reduce uncertainties in the calculations of carbon stocks and fluxes associated with the terrestrial biosphere. Biomass addresses one of the most fundamental questions in our understanding of the land component in the Earth system, namely the status and the dynamics of forests, as represented by the distribution of biomass and how it is changing. Gaining accurate and frequent information on forest properties at scales that allow changes to be observed will mean that the scientific community is equipped to address a range of critical issues with far-reaching benefits for science and society. Moreover, Biomass will greatly improve our knowledge of the size and distribution of the terrestrial carbon pool, and provide much-improved estimates of terrestrial carbon fluxes. In addition, the mission responds to the pressing need for biomass observations in support of global treaties such as the United Nations Framework Convention on Climate Change initiative for the Reduction of Emissions due to Deforestation and Forest Degradation. These mission objectives respond directly to the specific scientific challenges in ESA's Living Planet Programme. The emission of carbon dioxide to the atmosphere by human activity has been recognised as the major driver in climate change. Terrestrial ecosystems play an important role, both in the release of carbon through land use and deforestation and in the sequestration of carbon through vegetation growth processes. There is strong evidence that the terrestrial biosphere has acted as a net carbon sink over the last 30 years, removing from the atmosphere approximately one third of the carbon dioxide emitted from the combustion of fossil fuel. Nevertheless, terrestrial ecosystems are the largest source of uncertainty in the global carbon budget. Uncertainties lie in the spatial distribution of carbon stocks and carbon exchange, and in the estimates of carbon emissions resulting from human activity and natural processes. A central parameter in the terrestrial carbon budget is forest biomass, which is a proxy for carbon. Despite its crucial role in the terrestrial carbon budget, forest biomass in most parts of the world is poorly quantified owing to the difficulties in taking measurements from the ground and the lack in consistency when aggregating measurements across scales. Biomass will be implemented as a P-band Synthetic Aperture Radar (SAR) mission. It will exploit the unique sensitivity of P-band SAR together with advanced retrieval methods to measure forest biomass, height and disturbance across the entire biomass range every six months. The resolution and accuracy of the Biomass products will be compatible with the needs of international reporting on carbon stocks and terrestrial carbon models. In addition, Biomass will provide the first opportunity to explore Earth's surface using the P-band wavelength. The data are also expected to be used for monitoring glacier and ice sheet velocities, mapping subsurface geology in deserts and mapping the topography of forest floors. Additional products and applications are likely to emerge and be evaluated during the life of the mission...

    @TechReport{queganLeToanChaveDallPapathanassiouRoccaUlanderWilliamsESA2012BIOMASSReportforMissionSelection,
    author = {Shaun Quegan and Thuy Le Toan and J{\'e}r{\^o}me Chave and Jorgen Dall and Konstantinos P. Papathanassiou and Fabio Rocca and Lars Ulander and Mathew Williams},
    title = {Report for {M}ission {S}election: {B}iomass},
    institution = {ESA},
    year = {2012},
    number = {SP-1324/1 (3 volume series)},
    address = {Noordwijk, The Netherlands},
    month = May,
    abstract = {The Earth Explorer Biomass mission will provide the scientific community with the first accurate maps of tropical, temperate and boreal forest biomass, including height and disturbance patterns. This information is urgently needed to improve our understanding of the global carbon cycle and to reduce uncertainties in the calculations of carbon stocks and fluxes associated with the terrestrial biosphere. Biomass addresses one of the most fundamental questions in our understanding of the land component in the Earth system, namely the status and the dynamics of forests, as represented by the distribution of biomass and how it is changing. Gaining accurate and frequent information on forest properties at scales that allow changes to be observed will mean that the scientific community is equipped to address a range of critical issues with far-reaching benefits for science and society. Moreover, Biomass will greatly improve our knowledge of the size and distribution of the terrestrial carbon pool, and provide much-improved estimates of terrestrial carbon fluxes. In addition, the mission responds to the pressing need for biomass observations in support of global treaties such as the United Nations Framework Convention on Climate Change initiative for the Reduction of Emissions due to Deforestation and Forest Degradation. These mission objectives respond directly to the specific scientific challenges in ESA's Living Planet Programme. The emission of carbon dioxide to the atmosphere by human activity has been recognised as the major driver in climate change. Terrestrial ecosystems play an important role, both in the release of carbon through land use and deforestation and in the sequestration of carbon through vegetation growth processes. There is strong evidence that the terrestrial biosphere has acted as a net carbon sink over the last 30 years, removing from the atmosphere approximately one third of the carbon dioxide emitted from the combustion of fossil fuel. Nevertheless, terrestrial ecosystems are the largest source of uncertainty in the global carbon budget. Uncertainties lie in the spatial distribution of carbon stocks and carbon exchange, and in the estimates of carbon emissions resulting from human activity and natural processes. A central parameter in the terrestrial carbon budget is forest biomass, which is a proxy for carbon. Despite its crucial role in the terrestrial carbon budget, forest biomass in most parts of the world is poorly quantified owing to the difficulties in taking measurements from the ground and the lack in consistency when aggregating measurements across scales. Biomass will be implemented as a P-band Synthetic Aperture Radar (SAR) mission. It will exploit the unique sensitivity of P-band SAR together with advanced retrieval methods to measure forest biomass, height and disturbance across the entire biomass range every six months. The resolution and accuracy of the Biomass products will be compatible with the needs of international reporting on carbon stocks and terrestrial carbon models. In addition, Biomass will provide the first opportunity to explore Earth's surface using the P-band wavelength. The data are also expected to be used for monitoring glacier and ice sheet velocities, mapping subsurface geology in deserts and mapping the topography of forest floors. Additional products and applications are likely to emerge and be evaluated during the life of the mission...},
    file = {:SP1324-1_BIOMASSr.pdf:PDF},
    isbn = {978-92-9221-422-7},
    keywords = {BIOMASS, BIOMASS MISSION, ESA, European Space Agency, P-Band, Spaceborne SAR, SAR},
    owner = {ofrey},
    pdf = {../../../docs/SP1324-1_BIOMASSr.pdf},
    url = {http://esamultimedia.esa.int/docs/EarthObservation/SP1324-1_BIOMASSr.pdf},
    
    }
    


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Last modified: Mon Feb 1 16:39:00 2021
Author: Othmar Frey, Earth Observation and Remote Sensing, Institute of Environmental Engineering, Swiss Federal Institute of Technology - ETH Zurich .


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