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Publications of year 2014

Thesis

  1. Craig L. Stringham. Developments in LFM-CW SAR for UAV Operation. PhD thesis, 2014. Keyword(s): SAR Proceessing, radar, SAR, UAV, GPU, Autofocus, SAR Autofocus, Backprojection, Time-Domain Back-Projection, Back-Projection, TDBP, fast-factorized back-projection, FFBP, LFM-CW, FMCW, MoComp, Motion Compensation, CSA, ECS, Chirp Scaling, Extended Chirp Scaling, FSA, Frequency Scaling Algorithm, Range-Doppler Algorithm, RDA, synthetic aperture radar, Brigham Young University, muSAR system, LFM-CW signal model, SAR image quality, aircraft, atmospheric turbulence, high-resolution synthetic aperture radar systems, linear frequency-modulated continuous-wave signal, motion compensation, motion correction algorithms, unmanned aerial vehicle, Airborne SAR, geophysical techniques.
    Abstract: Opportunities to use synthetic aperture radar (SAR) in scientific studies and military operations are expanding with the development of small SAR systems that can be operated on small unmanned air vehicles (UAV)s. While the nimble nature of small UAVs make them an attractive platform for many reasons, small UAVs are also more prone to deviate from a linear course due autopilot errors and external forces such as turbulence and wind. Thus, motion compensation and improved processing algorithms are required to properly focus the SAR images. The work of this dissertation overcomes some of the challenges and addresses some of the opportunities of operating SAR on small UAVs. Several contributions to SAR backprojection processing for UAV SARs are developed including: 1. The derivation of a novel SAR backprojection algorithm that accounts for motion during the pulse that is appropriate for narrow or ultra-wide-band SAR. 2. A compensation method for SAR backprojection to enable radiometrically accurate image processing. 3. The design and implementation of a real-time backprojection processor on a commercially available GPU that takes advantage of the GPU texture cache. 4. A new auto-focus method that improves the image focus by estimating motion measurement errors in three dimensions, correcting for both amplitude and phase errors caused by inaccurate motion parameters. 5. A generalization of factorized backprojection, which we call the Dually Factorized Backprojection method, that factorizes the correlation integral in both slow-time and fast-time in order to eciently account for general motion during the transmit of an LFM-CW pulse. Much of this work was conducted in support of the Characterization of Arctic Sea Ice Experiment (CASIE), and the appendices provide substantial contributions for this project as well, including: 1. My work in designing and implementing the digital receiver and controller board for the microASAR which was used for CASIE. 2. A description of how the GPU backprojection was used to improved the CASIE imagery. 3. A description of a sample SAR data set from CASIE provided to the public to promote further SAR research.

    @PhdThesis{stringhamPhDThesis2014LFMCWSARProcessingForUAVOperation,
    author = {Craig L. Stringham},
    title = {Developments in {LFM-CW} {SAR} for {UAV} Operation},
    year = {2014},
    abstract = {Opportunities to use synthetic aperture radar (SAR) in scientific studies and military operations are expanding with the development of small SAR systems that can be operated on small unmanned air vehicles (UAV)s. While the nimble nature of small UAVs make them an attractive platform for many reasons, small UAVs are also more prone to deviate from a linear course due autopilot errors and external forces such as turbulence and wind. Thus, motion compensation and improved processing algorithms are required to properly focus the SAR images. The work of this dissertation overcomes some of the challenges and addresses some of the opportunities of operating SAR on small UAVs. Several contributions to SAR backprojection processing for UAV SARs are developed including: 1. The derivation of a novel SAR backprojection algorithm that accounts for motion during the pulse that is appropriate for narrow or ultra-wide-band SAR. 2. A compensation method for SAR backprojection to enable radiometrically accurate image processing. 3. The design and implementation of a real-time backprojection processor on a commercially available GPU that takes advantage of the GPU texture cache. 4. A new auto-focus method that improves the image focus by estimating motion measurement errors in three dimensions, correcting for both amplitude and phase errors caused by inaccurate motion parameters. 5. A generalization of factorized backprojection, which we call the Dually Factorized Backprojection method, that factorizes the correlation integral in both slow-time and fast-time in order to eciently account for general motion during the transmit of an LFM-CW pulse. Much of this work was conducted in support of the Characterization of Arctic Sea Ice Experiment (CASIE), and the appendices provide substantial contributions for this project as well, including: 1. My work in designing and implementing the digital receiver and controller board for the microASAR which was used for CASIE. 2. A description of how the GPU backprojection was used to improved the CASIE imagery. 3. A description of a sample SAR data set from CASIE provided to the public to promote further SAR research.},
    date = {Dec. 2014},
    file = {:stringhamPhDThesis2014LFMCWSARProcessingForUAVOperation.pdf:PDF},
    institution = {Brigham Young University},
    keywords = {SAR Proceessing, radar, SAR, UAV, GPU, Autofocus, SAR Autofocus, Backprojection,Time-Domain Back-Projection, Back-Projection, TDBP, fast-factorized back-projection, FFBP, LFM-CW, FMCW,MoComp, Motion Compensation, CSA, ECS, Chirp Scaling, Extended Chirp Scaling, FSA, Frequency Scaling Algorithm, Range-Doppler Algorithm, RDA, synthetic aperture radar, Brigham Young University, muSAR system, LFM-CW signal model, SAR image quality, aircraft, atmospheric turbulence, high-resolution synthetic aperture radar systems, linear frequency-modulated continuous-wave signal, motion compensation, motion correction algorithms, unmanned aerial vehicle, Airborne SAR, geophysical techniques},
    owner = {ofrey},
    pdf = {../../../docs/stringhamPhDThesis2014LFMCWSARProcessingForUAVOperation.pdf},
    url = {http://scholarsarchive.byu.edu/etd/5587},
    
    }
    


Articles in journal or book chapters

  1. Rafael Caduff, Andrew Kos, Fritz Schlunegger, Brian W. McArdell, and Andreas Wiesmann. Terrestrial Radar Interferometric Measurement of Hillslope Deformation and Atmospheric Disturbances in the Illgraben Debris-Flow Catchment, Switzerland. IEEE Geoscience and Remote Sensing Letters, 11(2):434-438, February 2014. Keyword(s): Atmospheric phase delay, rockslide monitoring, terrestrial radar interferometry, Radar interferometry, Gamma Portable Radar Interferometer, GPRI, Ku-band, Deformation, Displacement, Illgraben, Debris-flow catchment.
    @Article{caduffKosSchluneggerMcArdellWiesmannGRSL2014TRIGPRIDisplacementAtmoIllgrabenDebriFlowCatchment,
    author = {Rafael Caduff and Andrew Kos and Fritz Schlunegger and Brian W. McArdell and Andreas Wiesmann},
    journal = {{IEEE} Geoscience and Remote Sensing Letters},
    title = {Terrestrial Radar Interferometric Measurement of Hillslope Deformation and Atmospheric Disturbances in the {Illgraben} Debris-Flow Catchment, {Switzerland}},
    year = {2014},
    month = feb,
    number = {2},
    pages = {434--438},
    volume = {11},
    doi = {10.1109/LGRS.2013.2264564},
    file = {:caduffKosSchluneggerMcArdellWiesmannGRSL2014TRIGPRIDisplacementAtmoIllgrabenDebriFlowCatchment.pdf:PDF},
    keywords = {Atmospheric phase delay, rockslide monitoring,terrestrial radar interferometry, Radar interferometry, Gamma Portable Radar Interferometer, GPRI, Ku-band, Deformation, Displacement, Illgraben, Debris-flow catchment},
    owner = {ofrey},
    publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
    
    }
    


  2. Rafael Caduff and Dirk Rieke-Zapp. Registration And Visualisation Of Deformation Maps From Terrestrial Radar Interferometry Using Photogrammetry And Structure From Motion. The Photogrammetric Record, 29(146):167-186, 2014. Keyword(s): compact digital camera, digital photogrammetry, geo-monitoring, interferometric radar, metric camera, structure from motion, SAR Processing, Gamma Portable Radar Interferometer, GPRI, radar interferometry, ground-based radar, GBSAR, InSAR, Ground-based SAR, deformation measurement, displacement, subsidence, terrestrial radar interferometry, mass movements, surface deformation, Structure from motion, SfM, Photogrammetry.
    Abstract: This paper describes a general workflow for the registration of terrestrial radar interferometric data with 3D point clouds derived from terrestrial photogrammetry and structure from motion. After the determination of intrinsic and extrinsic orientation parameters, data obtained by terrestrial radar interferometry were projected on point clouds and then on the initial photographs. Visualisation of slope deformation measurements on photographs provides an easily understandable and distributable information product, especially of inaccessible target areas such as steep rock walls or in rockfall run-out zones. The suitability and error propagation of the referencing steps and final visualisation of four approaches are compared: (a) the classic approach using a metric camera and stereo-image photogrammetry; (b) images acquired with a metric camera, automatically processed using structure from motion; (c) images acquired with a digital compact camera, processed with structure from motion; and (d) a markerless approach, using images acquired with a digital compact camera using structure from motion without artificial ground control points. The usability of the completely markerless approach for the visualisation of high-resolution radar interferometry assists the production of visualisation products for interpretation.

    @Article{caduffRiekeZapp2014GPRIRegistrPhotogrammetry,
    author = {Caduff, Rafael and Rieke-Zapp, Dirk},
    title = {Registration And Visualisation Of Deformation Maps From Terrestrial Radar Interferometry Using Photogrammetry And Structure From Motion},
    journal = {The Photogrammetric Record},
    year = {2014},
    volume = {29},
    number = {146},
    pages = {167--186},
    issn = {1477-9730},
    abstract = {This paper describes a general workflow for the registration of terrestrial radar interferometric data with 3D point clouds derived from terrestrial photogrammetry and structure from motion. After the determination of intrinsic and extrinsic orientation parameters, data obtained by terrestrial radar interferometry were projected on point clouds and then on the initial photographs. Visualisation of slope deformation measurements on photographs provides an easily understandable and distributable information product, especially of inaccessible target areas such as steep rock walls or in rockfall run-out zones. The suitability and error propagation of the referencing steps and final visualisation of four approaches are compared: (a) the classic approach using a metric camera and stereo-image photogrammetry; (b) images acquired with a metric camera, automatically processed using structure from motion; (c) images acquired with a digital compact camera, processed with structure from motion; and (d) a markerless approach, using images acquired with a digital compact camera using structure from motion without artificial ground control points. The usability of the completely markerless approach for the visualisation of high-resolution radar interferometry assists the production of visualisation products for interpretation.},
    doi = {10.1111/phor.12058},
    file = {:caduffRiekeZapp2014GPRIRegistrPhotogrammetry.pdf:PDF},
    keywords = {compact digital camera, digital photogrammetry, geo-monitoring, interferometric radar, metric camera, structure from motion,SAR Processing, Gamma Portable Radar Interferometer, GPRI, radar interferometry, ground-based radar, GBSAR, InSAR, Ground-based SAR, deformation measurement, displacement, subsidence, terrestrial radar interferometry, mass movements, surface deformation, Structure from motion,SfM, Photogrammetry},
    pdf = {../../../docs/caduffRiekeZapp2014GPRIRegistrPhotogrammetry.pdf},
    url = {http://dx.doi.org/10.1111/phor.12058},
    
    }
    


  3. Estelle Chaussard, R Bürgmann, Manoochehr Shirzaei, EJ Fielding, and B Baker. Predictability of hydraulic head changes and characterization of aquifer-system and fault properties from InSAR-derived ground deformation. Journal of Geophysical Research: Solid Earth, 119(8):6572-6590, 2014.
    @Article{Chaussard2014,
    author = {Chaussard, Estelle and B{\"u}rgmann, R and Shirzaei, Manoochehr and Fielding, EJ and Baker, B},
    title = {Predictability of hydraulic head changes and characterization of aquifer-system and fault properties from InSAR-derived ground deformation},
    year = {2014},
    volume = {119},
    number = {8},
    pages = {6572--6590},
    journal = {Journal of Geophysical Research: Solid Earth},
    owner = {ofrey},
    publisher = {Wiley Online Library},
    
    }
    


  4. A. Elsherbini and K. Sarabandi. Image Distortion Effects in SAR Subsurface Imaging and a New Iterative Approach for Refocusing and Coregistration. IEEE_J_GRS, 52(5):2994-3004, May 2014. Keyword(s): SAR Processing, geophysical image processing, geophysical prospecting, groundwater, image registration, image resolution, radar interferometry, remote sensing by radar, synthetic aperture radar, topography (Earth), 3D simulations, InSAR concept, SAR subsurface imaging, archaeological surveys, ground water exploration, image aberrations, image coregistration, image distortion effects, image refocusing, image resolution, interferometric synthetic aperture radar, iterative approach, oil field exploration, phase front distortion, topography estimation, Focusing, History, Radar imaging, Surfaces, Synthetic aperture radar, Interferometric synthetic aperture radar (InSAR), radar imaging, subsurface imaging, terrain mapping.
    @Article{Elsherbini2014,
    author = {A. Elsherbini and K. Sarabandi},
    title = {Image Distortion Effects in {SAR} Subsurface Imaging and a New Iterative Approach for Refocusing and Coregistration},
    journal = IEEE_J_GRS,
    year = {2014},
    volume = {52},
    number = {5},
    pages = {2994--3004},
    month = may,
    issn = {0196-2892},
    doi = {10.1109/TGRS.2013.2268388},
    keywords = {SAR Processing, geophysical image processing, geophysical prospecting, groundwater, image registration, image resolution, radar interferometry, remote sensing by radar, synthetic aperture radar, topography (Earth), 3D simulations, InSAR concept, SAR subsurface imaging, archaeological surveys, ground water exploration, image aberrations, image coregistration, image distortion effects, image refocusing, image resolution, interferometric synthetic aperture radar, iterative approach, oil field exploration, phase front distortion, topography estimation, Focusing, History, Radar imaging, Surfaces, Synthetic aperture radar, Interferometric synthetic aperture radar (InSAR), radar imaging, subsurface imaging, terrain mapping},
    owner = {ofrey},
    
    }
    


  5. Gianfranco Fornaro, Fabrizio Lombardini, Antonio Pauciullo, Diego Reale, and Federico Viviani. Tomographic Processing of Interferometric SAR Data: Developments, applications, and future research perspectives. IEEE Signal Processing Magazine, 31(4):41-50, July 2014. Keyword(s): SAR Processing, SAR Tomography, PSI, Persistent Scatterer Interferometry, Deformation Monitoring, Deformation, radar interferometry, synthetic aperture radar, tomography, 3D reconstruction, classical multipass interferometric processing, environmental risk monitoring, interferometric SAR data tomographic processing, long-term deformation monitoring capability, natural hazard monitoring, synthetic aperture radar tomography techniques, three-dimensional reconstruction, Backscatter, Interferometry, Monitoring, Scattering, Synthetic aperture radar, Tomography.
    Abstract: Synthetic aperture radar (SAR) data processed with interferometric techniques are widely used today for environmental risk monitoring and security. SAR tomography techniques are a recent advance that provide improved three-dimensional (3-D) reconstruction and long-term deformation monitoring capabilities. This article is meant to discuss the main developments achieved in the last few years in the SAR tomography framework, with particular reference to both urban and forest scenarios. An insight on classical multipass interferometric processing is also included to summarize the importance of the technology for natural hazards monitoring and to provide the basis for the description of SAR tomography.

    @Article{fornaroLombardiniPauciulloRealeVivianiIEEESigProcMag2014TomoSAR,
    author = {Fornaro, Gianfranco and Lombardini, Fabrizio and Pauciullo, Antonio and Reale, Diego and Viviani, Federico},
    title = {Tomographic Processing of Interferometric {SAR} Data: Developments, applications, and future research perspectives},
    journal = {IEEE Signal Processing Magazine},
    year = {2014},
    volume = {31},
    number = {4},
    pages = {41-50},
    month = jul,
    issn = {1053-5888},
    abstract = {Synthetic aperture radar (SAR) data processed with interferometric techniques are widely used today for environmental risk monitoring and security. SAR tomography techniques are a recent advance that provide improved three-dimensional (3-D) reconstruction and long-term deformation monitoring capabilities. This article is meant to discuss the main developments achieved in the last few years in the SAR tomography framework, with particular reference to both urban and forest scenarios. An insight on classical multipass interferometric processing is also included to summarize the importance of the technology for natural hazards monitoring and to provide the basis for the description of SAR tomography.},
    doi = {10.1109/MSP.2014.2312073},
    file = {:fornaroLombardiniPauciulloRealeVivianiIEEESigProcMag2014TomoSAR.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, PSI, Persistent Scatterer Interferometry, Deformation Monitoring, Deformation, radar interferometry;synthetic aperture radar;tomography;3D reconstruction;classical multipass interferometric processing;environmental risk monitoring;interferometric SAR data tomographic processing;long-term deformation monitoring capability;natural hazard monitoring;synthetic aperture radar tomography techniques;three-dimensional reconstruction;Backscatter;Interferometry;Monitoring;Scattering;Synthetic aperture radar;Tomography},
    owner = {ofrey},
    pdf = {../../../docs/fornaroLombardiniPauciulloRealeVivianiIEEESigProcMag2014TomoSAR.pdf},
    
    }
    


  6. Gianfranco Fornaro, Antonio Pauciullo, Diego Reale, and Simona Verde. Multilook SAR Tomography for 3-D Reconstruction and Monitoring of Single Structures Applied to COSMO-SKYMED Data. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 7(7):2776-2785, July 2014. Keyword(s): SAR Processing, SAR Tomography, Component Extraction And selection SAR, CEASAR, Spaceborne SAR, multilook SAR tomography, X-Band, Urban, Persistent Scatterer Interferometry, PSI, time series, geophysical image processing, image reconstruction, image resolution, optical tomography, radar imaging, radar interferometry, radar resolution, synthetic aperture radar, 3D reconstruction, COSMO-SKYMED dataset, Italy, Naples, Rome, building monitoring, classical DInSAR analysis, fine resolution analysis, infrastructure monitoring, multilook SAR tomography, scatterer detection, single structure monitoring, Interferometry, Monitoring, Scattering, Spatial resolution, Synthetic aperture radar, Tomography, 3D, 4D, and multi-D SAR imaging, COSMO-SKYMED (CSK), SAR tomography, (CAESAR), differential SAR tomography, principal component analysis (PCA), synthetic aperture radar (SAR).
    Abstract: With reference to the application to the imaging and monitoring of infrastructures and buildings in urban areas, SAR tomography has been mainly developed and tested at full resolution. In this work, we investigate the possibility related to the use of a multilook approach for fine resolution analysis of ground structures that combines SAR tomography and a method, CAESAR, recently proposed for classical DInSAR analysis at coarse resolution over large areas. Shown results, achieved by processing two 3 m spatial resolution (stripmap mode) COSMO-SKYMED datasets relative to the urban areas of Naples and Rome (Italy), clearly indicate that the proposed multilook-based method allows achieving an impressive density of detected scatterers over buildings and infrastructures, much higher than those achievable with standard full-resolution methods.

    @Article{fornaroPauciulloRealeVerdeJSTARS2014TomoCAESAR,
    author = {Fornaro, Gianfranco and Pauciullo, Antonio and Reale, Diego and Verde, Simona},
    title = {Multilook {SAR} Tomography for {3-D} Reconstruction and Monitoring of Single Structures Applied to {COSMO-SKYMED} Data},
    journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
    year = {2014},
    volume = {7},
    number = {7},
    pages = {2776-2785},
    month = jul,
    issn = {1939-1404},
    abstract = {With reference to the application to the imaging and monitoring of infrastructures and buildings in urban areas, SAR tomography has been mainly developed and tested at full resolution. In this work, we investigate the possibility related to the use of a multilook approach for fine resolution analysis of ground structures that combines SAR tomography and a method, CAESAR, recently proposed for classical DInSAR analysis at coarse resolution over large areas. Shown results, achieved by processing two 3 m spatial resolution (stripmap mode) COSMO-SKYMED datasets relative to the urban areas of Naples and Rome (Italy), clearly indicate that the proposed multilook-based method allows achieving an impressive density of detected scatterers over buildings and infrastructures, much higher than those achievable with standard full-resolution methods.},
    doi = {10.1109/JSTARS.2014.2316323},
    file = {:fornaroPauciulloRealeVerdeJSTARS2014TomoCAESAR.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Component Extraction And selection SAR, CEASAR, Spaceborne SAR, multilook SAR tomography, X-Band, Urban, Persistent Scatterer Interferometry, PSI, time series, geophysical image processing;image reconstruction;image resolution;optical tomography;radar imaging;radar interferometry; radar resolution;synthetic aperture radar;3D reconstruction; COSMO-SKYMED dataset;Italy;Naples;Rome;building monitoring;classical DInSAR analysis; fine resolution analysis;infrastructure monitoring;multilook SAR tomography;scatterer detection; single structure monitoring;Interferometry;Monitoring;Scattering;Spatial resolution;Synthetic aperture radar;Tomography;3D, 4D, and multi-D SAR imaging;COSMO-SKYMED (CSK);SAR tomography; (CAESAR);differential SAR tomography;principal component analysis (PCA);synthetic aperture radar (SAR)},
    pdf = {../../../docs/fornaroPauciulloRealeVerdeJSTARS2014TomoCAESAR.pdf},
    
    }
    


  7. Y. Gao, W. Yu, Y. Liu, R. Wang, and C. Shi. Sharpness-Based Autofocusing for Stripmap SAR Using an Adaptive-Order Polynomial Model. IEEE Geoscience and Remote Sensing Letters, 11(6):1086-1090, June 2014. Keyword(s): conjugate gradient methods, maximum likelihood estimation, optical focusing, polynomials, radar imaging, search problems, synthetic aperture radar, closed-form expression, airborne SAR data experiment, modified adaptive-order searching strategy, conjugate gradient algorithm, polynomial expansion coefficient, sharpness function gradient, maximum-posterior estimation, SAR, stripmap-mode synthetic aperture radar image data, adaptive-order polynomial model, image sharpness-based autofocusing technique, Synthetic aperture radar, Polynomials, Accuracy, Estimation, Azimuth, Adaptation models, Optimization, Autofocus, conjugate gradient method (CGM), sharpness, synthetic aperture radar (SAR), Autofocus, conjugate gradient method (CGM), sharpness, synthetic aperture radar (SAR).
    Abstract: A novel autofocusing technique is developed for image from stripmap-mode synthetic aperture radar (SAR) data. The approach is based on maximizing the image sharpness function that induces the solution to maximum-posterior estimation. In this letter, closed-form expressions are derived for the gradients of the sharpness function with respect to the coefficients of the polynomial expansion, which makes the use of conjugate gradient algorithm available. Additionally, we also design a modified adaptive-order searching strategy, and it helps to remarkably reduce the computational load while maintaining the accuracy. Real airborne SAR data experiments and comparisons demonstrate the validity and effectiveness of the proposed algorithm.

    @Article{gaoYuLiuWangShiGRSL2014SharpnessBasedAutofocusingStripmapSARUsingAdaptiveOrderPolynomialModel,
    author = {Y. {Gao} and W. {Yu} and Y. {Liu} and R. {Wang} and C. {Shi}},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    title = {Sharpness-Based Autofocusing for Stripmap {SAR} Using an Adaptive-Order Polynomial Model},
    year = {2014},
    issn = {1558-0571},
    month = {June},
    number = {6},
    pages = {1086-1090},
    volume = {11},
    abstract = {A novel autofocusing technique is developed for image from stripmap-mode synthetic aperture radar (SAR) data. The approach is based on maximizing the image sharpness function that induces the solution to maximum-posterior estimation. In this letter, closed-form expressions are derived for the gradients of the sharpness function with respect to the coefficients of the polynomial expansion, which makes the use of conjugate gradient algorithm available. Additionally, we also design a modified adaptive-order searching strategy, and it helps to remarkably reduce the computational load while maintaining the accuracy. Real airborne SAR data experiments and comparisons demonstrate the validity and effectiveness of the proposed algorithm.},
    doi = {10.1109/LGRS.2013.2286410},
    file = {:gaoYuLiuWangShiGRSL2014SharpnessBasedAutofocusingStripmapSARUsingAdaptiveOrderPolynomialModel.pdf:PDF},
    keywords = {conjugate gradient methods;maximum likelihood estimation;optical focusing;polynomials;radar imaging;search problems;synthetic aperture radar;closed-form expression;airborne SAR data experiment;modified adaptive-order searching strategy;conjugate gradient algorithm;polynomial expansion coefficient;sharpness function gradient;maximum-posterior estimation;SAR;stripmap-mode synthetic aperture radar image data;adaptive-order polynomial model;image sharpness-based autofocusing technique;Synthetic aperture radar;Polynomials;Accuracy;Estimation;Azimuth;Adaptation models;Optimization;Autofocus;conjugate gradient method (CGM);sharpness;synthetic aperture radar (SAR);Autofocus;conjugate gradient method (CGM);sharpness;synthetic aperture radar (SAR)},
    owner = {ofrey},
    
    }
    


  8. Paolo Ghelfi, Francesco Laghezza, Filippo Scotti, Giovanni Serafino, Amerigo Capria, Sergio Pinna, Daniel Onori, Claudio Porzi, Mirco Scaffardi, Antonio Malacarne, Valeria Vercesi, Emma Lazzeri, Fabrizio Berizzi, and Antonella Bogoni. A fully photonics-based coherent radar system. Nature, 507(7492):341-345, 2014. Keyword(s): Radar, Photonics, Photonics-based radar, radar design.
    Abstract: The next generation of radar systems must be photonic to obtain frequency flexibility and improved performance; here both generation and detection of radio signals are demonstrated in a successful field trial of a photonic-based radar system using aeroplanes.

    @Article{ghelfiEtAlNature2014PhotonicsBasedCoherentRadar,
    author = {Ghelfi, Paolo and Laghezza, Francesco and Scotti, Filippo and Serafino, Giovanni and Capria, Amerigo and Pinna, Sergio and Onori, Daniel and Porzi, Claudio and Scaffardi, Mirco and Malacarne, Antonio and Vercesi, Valeria and Lazzeri, Emma and Berizzi, Fabrizio and Bogoni, Antonella},
    title = {A fully photonics-based coherent radar system},
    journal = {Nature},
    year = {2014},
    volume = {507},
    number = {7492},
    pages = {341-345},
    issn = {1476-4687},
    abstract = {The next generation of radar systems must be photonic to obtain frequency flexibility and improved performance; here both generation and detection of radio signals are demonstrated in a successful field trial of a photonic-based radar system using aeroplanes.},
    doi = {10.1038/nature13078},
    file = {:ghelfiEtAlNature2014PhotonicsBasedCoherentRadar.pdf:PDF},
    keywords = {Radar, Photonics, Photonics-based radar, radar design},
    owner = {ofrey},
    url = {https://doi.org/10.1038/nature13078},
    
    }
    


  9. Scott Hensley, S. Oveisgharan, S. Saatchi, M. Simard, R. Ahmed, and Z. Haddad. An Error Model for Biomass Estimates Derived From Polarimetric Radar Backscatter. IEEE_J_GRS, 52(7):4065-4082, July 2014. Keyword(s): air pollution, carbon capture and storage, remote sensing by radar, vegetation, above ground biomass, basic imaging physics, biomass estimation accuracy, carbon flux measurement, carbon storage, disturbance quantification, ecosystem processes, error model, forest carbon inventories, forested areas, ground carbon, instrument parameter, mission parameter, notional Earth observing mission, polarimetric radar backscatter, radar polarimetric measurements, regrowth quantification, remote sensing measurements, Backscatter, Biological system modeling, Biomass, Radar measurements, Radar polarimetry, Signal to noise ratio, Backscatter error model, forest biomass, polarimetry, synthetic aperture radar (SAR).
    @Article{hensleyOveisgharanSaatchiSimardAhmedHaddadTGRS2014ErrorModelforBiomassFromPolarimetricBackscatter,
    author = {Scott Hensley and S. Oveisgharan and S. Saatchi and M. Simard and R. Ahmed and Z. Haddad},
    title = {An Error Model for Biomass Estimates Derived From Polarimetric Radar Backscatter},
    journal = IEEE_J_GRS,
    year = {2014},
    volume = {52},
    number = {7},
    pages = {4065--4082},
    month = jul,
    issn = {0196-2892},
    doi = {10.1109/TGRS.2013.2279400},
    file = {:hensleyOveisgharanSaatchiSimardAhmedHaddadTGRS2014ErrorModelforBiomassFromPolarimetricBackscatter.pdf:PDF},
    keywords = {air pollution, carbon capture and storage, remote sensing by radar, vegetation, above ground biomass, basic imaging physics, biomass estimation accuracy, carbon flux measurement, carbon storage, disturbance quantification, ecosystem processes, error model, forest carbon inventories, forested areas, ground carbon, instrument parameter, mission parameter, notional Earth observing mission, polarimetric radar backscatter, radar polarimetric measurements, regrowth quantification, remote sensing measurements, Backscatter, Biological system modeling, Biomass, Radar measurements, Radar polarimetry, Signal to noise ratio, Backscatter error model, forest biomass, polarimetry, synthetic aperture radar (SAR)},
    owner = {ofrey},
    
    }
    


  10. R. Iglesias, X. Fabregas, A. Aguasca, J. J. Mallorqui, C. Lopez-Martinez, J. A. Gili, and J. Corominas. Atmospheric Phase Screen Compensation in Ground-Based SAR With a Multiple-Regression Model Over Mountainous Regions. IEEE_J_GRS, 52(5):2436-2449, May 2014. Keyword(s): GB-SAR, ground-based SAR, terrestrial SAR, geophysical techniques, radar polarimetry, synthetic aperture radar, AD 2010 10 to 2011 10, Andorran Pyrenees, El Forn de Canillo, GB-SAR sensor, Universitat Politecnica de Catalunya, X-band, atmospheric fluctuations, atmospheric phase screen compensation process, differential-SAR-interferometry applications, ground-based SAR data, mountainous environment, mountainous regions, multiple-regression model, multitemporal GB-SAR measurements, one-year measurement campaign, polarimetric SAR data, steep topography effect, strong rain episodes, synthetic aperture radar, zero-baseline fully polarimetric data sets, Atmospheric phase screen (APS) compensation, differential synthetic aperture radar (SAR) interferometry (DInSAR), ground-based SAR (GB-SAR), polarimetry, steep topography.
    @Article{Iglesias2014,
    author = {R. Iglesias and X. Fabregas and A. Aguasca and J. J. Mallorqui and C. Lopez-Martinez and J. A. Gili and J. Corominas},
    title = {Atmospheric Phase Screen Compensation in Ground-Based {SAR} With a Multiple-Regression Model Over Mountainous Regions},
    journal = IEEE_J_GRS,
    year = {2014},
    volume = {52},
    number = {5},
    month = may,
    pages = {2436--2449},
    issn = {0196-2892},
    doi = {10.1109/TGRS.2013.2261077},
    keywords = {GB-SAR,ground-based SAR, terrestrial SAR,geophysical techniques, radar polarimetry, synthetic aperture radar, AD 2010 10 to 2011 10, Andorran Pyrenees, El Forn de Canillo, GB-SAR sensor, Universitat Politecnica de Catalunya, X-band, atmospheric fluctuations, atmospheric phase screen compensation process, differential-SAR-interferometry applications, ground-based SAR data, mountainous environment, mountainous regions, multiple-regression model, multitemporal GB-SAR measurements, one-year measurement campaign, polarimetric SAR data, steep topography effect, strong rain episodes, synthetic aperture radar, zero-baseline fully polarimetric data sets, Atmospheric phase screen (APS) compensation, differential synthetic aperture radar (SAR) interferometry (DInSAR), ground-based SAR (GB-SAR), polarimetry, steep topography},
    owner = {ofrey},
    
    }
    


  11. R. Iglesias, D. Monells, X. Fabregas, J. J. Mallorqui, A. Aguasca, and C. Lopez-Martinez. Phase Quality Optimization in Polarimetric Differential SAR Interferometry. IEEE Transactions on Geoscience and Remote Sensing, 52(5):2875-2888, May 2014. Keyword(s): geophysical techniques, optimisation, radar interferometry, radar polarimetry, remote sensing by radar, synthetic aperture radar, ALOS, DInSAR processing, DInSAR techniques, RADARSAT-2, TerraSAR-X, advanced land observing satellite, amplitude dispersion case, amplitude dispersion maps, classical single-polarimetric approach, coherence case, differential SAR interferometry, differential synthetic aperture radar interferometry, final DInSAR result density, final DInSAR result reliability, fully polarimetric data unavailability, ground-based SAR fully polarimetric data, interferometric technique merging, orbital SAR fully polarimetric data, phase quality optimization, pixel candidate number threefold, pixel phase quality, pixel selection process, polarimetric capabilities, polarimetric differential SAR interferometry, polarimetric optimization techniques, polarimetric technique merging, polarimetrically optimized coherence, satellite launch, single-polarimetric case, Amplitude dispersion optimization, coherence optimization, differential synthetic aperture radar (SAR) interferometry (DInSAR), polarimetric DInSAR (PolDInSAR), polarimetry.
    Abstract: In this paper, a study of polarimetric optimization techniques in the frame of differential synthetic aperture radar (SAR) interferometry (DInSAR) is considered. Historically, DInSAR techniques have been limited to the single-polarimetric case, mainly due to the unavailability of fully polarimetric data. Lately, the launch of satellites with polarimetric capabilities, such as the Advanced Land Observing Satellite (ALOS), RADARSAT-2, or TerraSAR-X, allowed merging polarimetric and interferometric techniques to improve the pixels' phase quality and, thus, the density and the reliability of the final DInSAR results. The relationship between the polarimetrically optimized coherence or amplitude dispersion maps and the final DInSAR results is carefully analyzed, using both orbital and ground-based SAR fully polarimetric data. DInSAR processing using polarimetric optimization techniques in the pixel selection process is compared with the classical single-polarimetric approach, achieving up to a threefold increase of the number of pixel candidates in the coherence case and up to a factor of seven in the amplitude dispersion case.

    @Article{iglesiasMonellsFabregasMallorquiAguascaLopezMartinezTGRS2014PhaseQualityOptInPolDInSAR,
    author = {R. Iglesias and D. Monells and X. Fabregas and J. J. Mallorqui and A. Aguasca and C. Lopez-Martinez},
    title = {Phase Quality Optimization in Polarimetric Differential SAR Interferometry},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2014},
    volume = {52},
    number = {5},
    pages = {2875-2888},
    month = may,
    issn = {0196-2892},
    abstract = {In this paper, a study of polarimetric optimization techniques in the frame of differential synthetic aperture radar (SAR) interferometry (DInSAR) is considered. Historically, DInSAR techniques have been limited to the single-polarimetric case, mainly due to the unavailability of fully polarimetric data. Lately, the launch of satellites with polarimetric capabilities, such as the Advanced Land Observing Satellite (ALOS), RADARSAT-2, or TerraSAR-X, allowed merging polarimetric and interferometric techniques to improve the pixels' phase quality and, thus, the density and the reliability of the final DInSAR results. The relationship between the polarimetrically optimized coherence or amplitude dispersion maps and the final DInSAR results is carefully analyzed, using both orbital and ground-based SAR fully polarimetric data. DInSAR processing using polarimetric optimization techniques in the pixel selection process is compared with the classical single-polarimetric approach, achieving up to a threefold increase of the number of pixel candidates in the coherence case and up to a factor of seven in the amplitude dispersion case.},
    doi = {10.1109/TGRS.2013.2267095},
    keywords = {geophysical techniques;optimisation;radar interferometry;radar polarimetry;remote sensing by radar;synthetic aperture radar;ALOS;DInSAR processing;DInSAR techniques;RADARSAT-2;TerraSAR-X;advanced land observing satellite;amplitude dispersion case;amplitude dispersion maps;classical single-polarimetric approach;coherence case;differential SAR interferometry;differential synthetic aperture radar interferometry;final DInSAR result density;final DInSAR result reliability;fully polarimetric data unavailability;ground-based SAR fully polarimetric data;interferometric technique merging;orbital SAR fully polarimetric data;phase quality optimization;pixel candidate number threefold;pixel phase quality;pixel selection process;polarimetric capabilities;polarimetric differential SAR interferometry;polarimetric optimization techniques;polarimetric technique merging;polarimetrically optimized coherence;satellite launch;single-polarimetric case;Amplitude dispersion optimization;coherence optimization;differential synthetic aperture radar (SAR) interferometry (DInSAR);polarimetric DInSAR (PolDInSAR);polarimetry},
    owner = {ofrey},
    
    }
    


  12. Uday K. Khankhoje, Mariko S. Burgin, and Mahta Moghaddam. On the Accuracy of Averaging Radar Backscattering Coefficients for Bare Soils Using the Finite-Element Method. IEEE Geoscience and Remote Sensing Letters, 11(8):1345-1349, August 2014. Keyword(s): finite element analysis, geophysical techniques, remote sensing by radar, soil, surface roughness, 2-D finite-element method, Gaussian correlated surfaces, Gaussian correlated surfaces possessing behavior, Gaussian type, assumption validity, average coefficients, averaging assumption, averaging radar backscattering coefficient accuracy, backscatter averaging assumption breaks, backscatter averaging assumption validity conditions, bare rough surface assumption validity, bare soils, constitutive homogeneous pixels, ensemble averaged true coefficient computation, exponential type, exponentially correlated surfaces, heterogeneity impact quantification, heterogeneity source, heterogeneous moisture pixels, heterogeneous pixels, heterogeneous roughness pixels, heterogeneous soil moisture, heterogeneous soil roughness, high-contrast pixels, higher cross-pixel coherent interactions, longest correlation lengths, soil moisture, soil surface roughness, surface correlation type, surface variety computed averages, Backscatter, Correlation, Radar, Rough surfaces, Soil moisture, Surface roughness, Electromagnetic scattering by rough surfaces, finite-element methods (FEMs).
    Abstract: Radar backscattering coefficients for heterogeneous pixels are traditionally assumed to be the average of the coefficients for the constitutive homogeneous pixels. We investigate the validity of this assumption for bare rough surfaces by using the 2-D finite-element method to compute the ensemble averaged true coefficients for heterogeneous pixels and compare these values with the computed averages for a variety of surfaces. We quantify the impact of heterogeneity in both soil moisture and surface roughness on the averaging assumption. We find that the validity of the assumption rests crucially on the surface correlation type (exponential or Gaussian) and length. In particular, when considering pixels with either heterogeneous soil moisture or roughness, we find that for high-contrast pixels, the backscatter averaging assumption breaks down by as much as 11 dB for Gaussian correlated surfaces for the longest correlation lengths considered (regardless of the source of heterogeneity), whereas for exponentially correlated surfaces, it breaks down by 6 dB for pixels with heterogeneous roughness and 2 dB for pixels with heterogeneous moisture. We attribute this behavior to Gaussian correlated surfaces possessing higher cross-pixel coherent interactions. Furthermore, conditions of validity for the backscatter averaging assumption are identified.

    @Article{khankhojeBurginMoghaddamGRSL2014RadarBackScatterFEMMethod,
    author = {Uday K. Khankhoje and Mariko S. Burgin and Mahta Moghaddam},
    title = {On the Accuracy of Averaging Radar Backscattering Coefficients for Bare Soils Using the Finite-Element Method},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    year = {2014},
    volume = {11},
    number = {8},
    pages = {1345-1349},
    month = aug,
    issn = {1545-598X},
    abstract = {Radar backscattering coefficients for heterogeneous pixels are traditionally assumed to be the average of the coefficients for the constitutive homogeneous pixels. We investigate the validity of this assumption for bare rough surfaces by using the 2-D finite-element method to compute the ensemble averaged true coefficients for heterogeneous pixels and compare these values with the computed averages for a variety of surfaces. We quantify the impact of heterogeneity in both soil moisture and surface roughness on the averaging assumption. We find that the validity of the assumption rests crucially on the surface correlation type (exponential or Gaussian) and length. In particular, when considering pixels with either heterogeneous soil moisture or roughness, we find that for high-contrast pixels, the backscatter averaging assumption breaks down by as much as 11 dB for Gaussian correlated surfaces for the longest correlation lengths considered (regardless of the source of heterogeneity), whereas for exponentially correlated surfaces, it breaks down by 6 dB for pixels with heterogeneous roughness and 2 dB for pixels with heterogeneous moisture. We attribute this behavior to Gaussian correlated surfaces possessing higher cross-pixel coherent interactions. Furthermore, conditions of validity for the backscatter averaging assumption are identified.},
    doi = {10.1109/LGRS.2013.2293392},
    file = {:khankhojeBurginMoghaddamGRSL2014RadarBackScatterFEMMethod.pdf:PDF},
    keywords = {finite element analysis;geophysical techniques;remote sensing by radar;soil;surface roughness;2-D finite-element method;Gaussian correlated surfaces;Gaussian correlated surfaces possessing behavior;Gaussian type;assumption validity;average coefficients;averaging assumption;averaging radar backscattering coefficient accuracy;backscatter averaging assumption breaks;backscatter averaging assumption validity conditions;bare rough surface assumption validity;bare soils;constitutive homogeneous pixels;ensemble averaged true coefficient computation;exponential type;exponentially correlated surfaces;heterogeneity impact quantification;heterogeneity source;heterogeneous moisture pixels;heterogeneous pixels;heterogeneous roughness pixels;heterogeneous soil moisture;heterogeneous soil roughness;high-contrast pixels;higher cross-pixel coherent interactions;longest correlation lengths;soil moisture;soil surface roughness;surface correlation type;surface variety computed averages;Backscatter;Correlation;Radar;Rough surfaces;Soil moisture;Surface roughness;Electromagnetic scattering by rough surfaces;finite-element methods (FEMs)},
    
    }
    


  13. S. B. Kim, Mahta Moghaddam, L. Tsang, Mariko S. Burgin, X. Xu, and E. G. Njoku. Models of L-Band Radar Backscattering Coefficients Over Global Terrain for Soil Moisture Retrieval. IEEE Transactions on Geoscience and Remote Sensing, 52(2):1381-1396, February 2014. Keyword(s): Maxwell equations, permittivity, remote sensing by radar, soil, time series, vegetation mapping, L-band radar backscattering coefficient models, Maxwell equations, RMS height, VWC, accurate soil moisture inversion, airborne data, airborne observation, bare surface, co-pol RMS errors, corn crop, datacube errors, dielectric soil constant, distorted Born approximation framework, double-bounce reflectivity, double-bounce volume-surface interaction, empirical formulae, empirical parameters, fast soil moisture inversion, field-based radar data, global land surface, global terrain, grass fields, in situ observation, independent spaceborne phased array type L-band synthetic aperture radars, input parameters, international geosphere-biosphere programme scheme, land surface class simulation, lookup tables, major crops, mean difference range, numerical solutions, physical model outputs, real-time soil moisture inversion, rice crop, shrub, single scatterer, soil moisture active passive mission data, soil moisture retrieval, soil surface root mean square, sophisticated forward model direct inversion, soybean crop, spaceborne Aquarius scatterometer data, surface scattering, theoretical models.
    Abstract: Physical models for radar backscattering coefficients are developed for the global land surface at L-band (1.26 GHz) and 40 deg incidence angle to apply to the soil moisture retrieval from the upcoming soil moisture active passive mission data. The simulation of land surface classes includes 12 vegetation types defined by the International Geosphere-Biosphere Programme scheme, and four major crops (wheat, corn, rice, and soybean). Backscattering coefficients for four polarizations (HH/VV/HV/VH) are produced. In the physical models, three terms are considered within the framework of distorted Born approximation: surface scattering, double-bounce volume-surface interaction, and volume scattering. Numerical solutions of Maxwell equations as well as theoretical models are used for surface scattering, double-bounce reflectivity, and volume scattering of a single scatterer. To facilitate fast, real-time, and accurate inversion of soil moisture, the outputs of physical model are provided as lookup tables (with three axes; therefore called datacube). The three axes are the real part of the dielectric constant of soil, soil surface root mean square (RMS) height, and vegetation water content (VWC), each of, which covers the wide range of natural conditions. Datacubes for most of the classes are simulated using input parameters from in situ and airborne observations. This simulation results are found accurate to the co-pol RMS errors of to 3.4 dB (six woody vegetation types), 1.8 dB (grass), and 2.9 dB (corn) when compared with airborne data. Validated with independent spaceborne phased array type L-band synthetic aperture radars and field-based radar data, the datacube errors for the co-pols are within 3.4 dB (woody savanna and shrub) and 1.5 dB (bare surface). Assessed with spaceborne Aquarius scatterometer data, the mean differences range from ~ 1.5 to 2 dB. The datacubes allow direct inversion of sophisticated forward models without empirical par- meters or formulae. This capability is evaluated using the time-series inversion algorithm over grass fields.

    @Article{kimMoghaddamTsangBurginXuNjokuTGRS2014ModelLBandBackscatteringOverGlobalTerrainForSoilMoisture,
    author = {S. B. Kim and Mahta Moghaddam and L. Tsang and Mariko S. Burgin and X. Xu and E. G. Njoku},
    title = {Models of {L}-Band Radar Backscattering Coefficients Over Global Terrain for Soil Moisture Retrieval},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2014},
    volume = {52},
    number = {2},
    pages = {1381-1396},
    month = feb,
    issn = {0196-2892},
    abstract = {Physical models for radar backscattering coefficients are developed for the global land surface at L-band (1.26 GHz) and 40 deg incidence angle to apply to the soil moisture retrieval from the upcoming soil moisture active passive mission data. The simulation of land surface classes includes 12 vegetation types defined by the International Geosphere-Biosphere Programme scheme, and four major crops (wheat, corn, rice, and soybean). Backscattering coefficients for four polarizations (HH/VV/HV/VH) are produced. In the physical models, three terms are considered within the framework of distorted Born approximation: surface scattering, double-bounce volume-surface interaction, and volume scattering. Numerical solutions of Maxwell equations as well as theoretical models are used for surface scattering, double-bounce reflectivity, and volume scattering of a single scatterer. To facilitate fast, real-time, and accurate inversion of soil moisture, the outputs of physical model are provided as lookup tables (with three axes; therefore called datacube). The three axes are the real part of the dielectric constant of soil, soil surface root mean square (RMS) height, and vegetation water content (VWC), each of, which covers the wide range of natural conditions. Datacubes for most of the classes are simulated using input parameters from in situ and airborne observations. This simulation results are found accurate to the co-pol RMS errors of to 3.4 dB (six woody vegetation types), 1.8 dB (grass), and 2.9 dB (corn) when compared with airborne data. Validated with independent spaceborne phased array type L-band synthetic aperture radars and field-based radar data, the datacube errors for the co-pols are within 3.4 dB (woody savanna and shrub) and 1.5 dB (bare surface). Assessed with spaceborne Aquarius scatterometer data, the mean differences range from ~ 1.5 to 2 dB. The datacubes allow direct inversion of sophisticated forward models without empirical par- meters or formulae. This capability is evaluated using the time-series inversion algorithm over grass fields.},
    doi = {10.1109/TGRS.2013.2250980},
    file = {:kimMoghaddamTsangBurginXuNjokuTGRS2014ModelLBandBackscatteringOverGlobalTerrainForSoilMoisture.pdf:PDF},
    keywords = {Maxwell equations;permittivity;remote sensing by radar;soil;time series;vegetation mapping;L-band radar backscattering coefficient models;Maxwell equations;RMS height;VWC;accurate soil moisture inversion;airborne data;airborne observation;bare surface;co-pol RMS errors;corn crop;datacube errors;dielectric soil constant;distorted Born approximation framework;double-bounce reflectivity;double-bounce volume-surface interaction;empirical formulae;empirical parameters;fast soil moisture inversion;field-based radar data;global land surface;global terrain;grass fields;in situ observation;independent spaceborne phased array type L-band synthetic aperture radars;input parameters;international geosphere-biosphere programme scheme;land surface class simulation;lookup tables;major crops;mean difference range;numerical solutions;physical model outputs;real-time soil moisture inversion;rice crop;shrub;single scatterer;soil moisture active passive mission data;soil moisture retrieval;soil surface root mean square;sophisticated forward model direct inversion;soybean crop;spaceborne Aquarius scatterometer data;surface scattering;theoretical models;time-series inversion algorithm;vegetation types;vegetation water content;volume scattering;wheat crop;wide range natural conditions;woody savanna;woody vegetation types;Radar scattering model;soil moisture;synthetic aperture radar (SAR)},
    
    }
    


  14. K. Landmark, A. H. Schistad Solberg, A. Austeng, and Roy E. Hansen. Bayesian Seabed Classification Using Angle-Dependent Backscatter Data From Multibeam Echo Sounders. IEEE Journal of Oceanic Engineering, 39(4):724-739, October 2014. Keyword(s): Synthetic Aperture Sonar, SAS, Bayes methods, Gaussian processes, acoustic wave scattering, approximation theory, backscatter, oceanographic techniques, pattern classification, piecewise constant techniques, sonar, statistical analysis, Bayesian seabed classification, Gaussian statistical model, North Sea data set, acoustical seabed classification, across-track spatial resolution, angle-dependent backscatter data, intrinsic scattering strength statistics, mapping seabed sediment, multibeam echo sounder, multibeam sonar data processing, piecewise constant function, piecewise function approximation, seabed scattering strength, spatial averaging, standard Bayesian theory, Bayes methods, Classification algorithms, Remote sensing, Sea floor, Sediments, Sonar, Underwater acoustics, Bayesian methods, classification algorithms, remote sensing, seafloor, sediments, sonar.
    Abstract: Acoustical seabed classification is a technology for mapping seabed sediments. Processed multibeam sonar data yield the variation of the seabed scattering strength with incidence angle, and this paper examines the effect of this on classification. A simple Gaussian statistical model is developed for the observed scattering strength, whereby an observation is represented by a piecewise constant function of incidence angle. Provided some data for which the sediment types are known (training data), the statistics for each type can be robustly estimated. Subsequently, a standard Bayesian theory is applied to classify new observations. The model was used to compute limits on classification accuracy in terms of the intrinsic scattering strength statistics of the seabed, and to predict whether a logarithmic or linear scale for the data is preferable. Systematic experiments on a North Sea data set with four sediment classes tested how the classification accuracy depends on the piecewise function approximation, incidence angle range, amount of training data, and spatial averaging (combining consecutive pings into one observation). The classifier based on Gaussian statistics performed at least as well as sophisticated algorithms with no assumptions about the data statistics. The best accuracy (95%) was attained for logarithmic data. The amount of training data needed to achieve this was about 500 pings per class; spatial averaging could be limited to 10-20 pings. Comparable across-track spatial resolution was possible by dividing the full swath into separate independent sectors, but only at reduced accuracy (87% or less). However, comparable accuracy may be possible by taking into account the spatial relationships of observations.

    @Article{landmarkSolbergAustengHansenJOE2014BayesianClassificationUsingMultibeamSounders,
    author = {K. Landmark and A. H. Schistad Solberg and A. Austeng and Roy E. Hansen},
    title = {Bayesian Seabed Classification Using Angle-Dependent Backscatter Data From Multibeam Echo Sounders},
    journal = {IEEE Journal of Oceanic Engineering},
    year = {2014},
    volume = {39},
    number = {4},
    pages = {724-739},
    month = {Oct},
    issn = {0364-9059},
    abstract = {Acoustical seabed classification is a technology for mapping seabed sediments. Processed multibeam sonar data yield the variation of the seabed scattering strength with incidence angle, and this paper examines the effect of this on classification. A simple Gaussian statistical model is developed for the observed scattering strength, whereby an observation is represented by a piecewise constant function of incidence angle. Provided some data for which the sediment types are known (training data), the statistics for each type can be robustly estimated. Subsequently, a standard Bayesian theory is applied to classify new observations. The model was used to compute limits on classification accuracy in terms of the intrinsic scattering strength statistics of the seabed, and to predict whether a logarithmic or linear scale for the data is preferable. Systematic experiments on a North Sea data set with four sediment classes tested how the classification accuracy depends on the piecewise function approximation, incidence angle range, amount of training data, and spatial averaging (combining consecutive pings into one observation). The classifier based on Gaussian statistics performed at least as well as sophisticated algorithms with no assumptions about the data statistics. The best accuracy (95%) was attained for logarithmic data. The amount of training data needed to achieve this was about 500 pings per class; spatial averaging could be limited to 10-20 pings. Comparable across-track spatial resolution was possible by dividing the full swath into separate independent sectors, but only at reduced accuracy (87% or less). However, comparable accuracy may be possible by taking into account the spatial relationships of observations.},
    doi = {10.1109/JOE.2013.2281133},
    file = {:landmarkSolbergAustengHansenJOE2014BayesianClassificationUsingMultibeamSounders.pdf:PDF},
    keywords = {Synthetic Aperture Sonar, SAS,Bayes methods;Gaussian processes;acoustic wave scattering;approximation theory;backscatter;oceanographic techniques;pattern classification;piecewise constant techniques;sonar;statistical analysis;Bayesian seabed classification;Gaussian statistical model;North Sea data set;acoustical seabed classification;across-track spatial resolution;angle-dependent backscatter data;intrinsic scattering strength statistics;mapping seabed sediment;multibeam echo sounder;multibeam sonar data processing;piecewise constant function;piecewise function approximation;seabed scattering strength;spatial averaging;standard Bayesian theory;Bayes methods;Classification algorithms;Remote sensing;Sea floor;Sediments;Sonar;Underwater acoustics;Bayesian methods;classification algorithms;remote sensing;seafloor;sediments;sonar},
    
    }
    


  15. H. Lee, J. H. Lee, K. E. Kim, N. H. Sung, and S. J. Cho. Development of a Truck-Mounted Arc-Scanning Synthetic Aperture Radar. IEEE Transactions on Geoscience and Remote Sensing, 52(5):2773-2779, May 2014. Keyword(s): GB-SAR, ground-based SAR, terrestrial SAR, Doppler radar, antennas, geophysical equipment, radar imaging, remote sensing by radar, synthetic aperture radar, ArcSAR formulation, ArcSAR scan mode image, ArcSAR system development, SAR focusing algorithms, antenna view angle fixing, arc-scanning real aperture radar, azimuth resolution, conventional ground-based SAR system linear scanning, exemplary X-band ArcSAR spot mode image, extendable boom, ground-based arc-scanning synthetic aperture radar development, high-resolution image, horizontal circular antenna motion, image area, image processing accuracy, image processing efficiency, imaging mode, range Doppler algorithm, reduced resolution, scan mode, time domain algorithm, truck-mounted arc-scanning synthetic aperture radar development, wider image coverage, Arc-scanning synthetic aperture radar (ArcSAR), SAR, range Doppler algorithm, scan mode, spot mode, time domain algorithm.
    Abstract: This paper presents the development of a ground-based arc-scanning synthetic aperture radar (ArcSAR) system mounted on a truck. ArcSAR formulates synthetic aperture by a horizontal circular motion of antennas attached at the end of an extendable boom. The ArcSAR system is designed to operate in two different imaging modes: the spot mode and the scan mode . The spot mode obtains a high-resolution image by fixing the view angle of antennas toward a target. The scan mode obtains wider image coverage with a reduced resolution by fixing the antennas relative to the boom. Different SAR focusing algorithms were implemented for the accuracy and efficiency of image processing: the time domain algorithm for the spot mode and the range Doppler algorithm for the scan mode. An exemplary X-band ArcSAR spot mode image, obtained with a 180 deg scanning of 4-m boom, has an azimuth resolution of 0.07 deg , which is equivalent to the 12.6-m linear scanning of a conventional ground-based SAR system. An ArcSAR scan mode image was successfully obtained as well, covering a 350 deg image area at an azimuth resolution of 1.07 deg, which is 11 times better than that of arc-scanning real aperture radar that would have 11.84 deg azimuth resolution.

    @Article{leeLeeKimSungChoTGARS2014ArcSARGBSAR,
    author = {H. Lee and J. H. Lee and K. E. Kim and N. H. Sung and S. J. Cho},
    title = {Development of a Truck-Mounted Arc-Scanning Synthetic Aperture Radar},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2014},
    volume = {52},
    number = {5},
    month = {May},
    pages = {2773-2779},
    issn = {0196-2892},
    doi = {10.1109/TGRS.2013.2265700},
    abstract = {This paper presents the development of a ground-based arc-scanning synthetic aperture radar (ArcSAR) system mounted on a truck. ArcSAR formulates synthetic aperture by a horizontal circular motion of antennas attached at the end of an extendable boom. The ArcSAR system is designed to operate in two different imaging modes: the spot mode and the scan mode . The spot mode obtains a high-resolution image by fixing the view angle of antennas toward a target. The scan mode obtains wider image coverage with a reduced resolution by fixing the antennas relative to the boom. Different SAR focusing algorithms were implemented for the accuracy and efficiency of image processing: the time domain algorithm for the spot mode and the range Doppler algorithm for the scan mode. An exemplary X-band ArcSAR spot mode image, obtained with a 180 deg scanning of 4-m boom, has an azimuth resolution of 0.07 deg , which is equivalent to the 12.6-m linear scanning of a conventional ground-based SAR system. An ArcSAR scan mode image was successfully obtained as well, covering a 350 deg image area at an azimuth resolution of 1.07 deg, which is 11 times better than that of arc-scanning real aperture radar that would have 11.84 deg azimuth resolution.},
    keywords = {GB-SAR,ground-based SAR, terrestrial SAR,Doppler radar;antennas;geophysical equipment;radar imaging;remote sensing by radar;synthetic aperture radar;ArcSAR formulation;ArcSAR scan mode image;ArcSAR system development;SAR focusing algorithms;antenna view angle fixing;arc-scanning real aperture radar;azimuth resolution;conventional ground-based SAR system linear scanning;exemplary X-band ArcSAR spot mode image;extendable boom;ground-based arc-scanning synthetic aperture radar development;high-resolution image;horizontal circular antenna motion;image area;image processing accuracy;image processing efficiency;imaging mode;range Doppler algorithm;reduced resolution;scan mode;time domain algorithm;truck-mounted arc-scanning synthetic aperture radar development;wider image coverage;Arc-scanning synthetic aperture radar (ArcSAR);SAR;range Doppler algorithm;scan mode;spot mode;time domain algorithm},
    owner = {ofrey},
    
    }
    


  16. Silvan Leinss, Giuseppe Parrella, and Irena Hajnsek. Snow height determination by polarimetric phase differences in X-band SAR data. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 7(9):3794-3810, Sept 2014. Keyword(s): hydrological techniques, remote sensing by radar, snow, synthetic aperture radar, AD 2012 01, AD 2012 12 to 2013 04, CPD temporal evolution, Finland, HH polarization, Sodankylae city, TanDEM-X, TanDEM-X acquisitions, TerraSAR-X acquisitions, VV polarization, X-band SAR acquisitions, X-band SAR data, aligned elliptical particles, computer tomography observations, copolar phase difference, fresh snow depth, polarimetric phase difference, snow height determination, snow microstructure, subsequent recrystallization process, temperature-gradient-driven recrystallization process, weather station data, Backscatter, Scattering, Snow, Soil, Soil measurements, Synthetic aperture radar, Temperature measurement, Birefringence, TanDEM-X, TerraSAR-X, VV-HH phase difference, copolar phase difference, dry snow, fresh snow, polarimetry, snow anisotropy, snow microstructure, synthetic aperture radar.
    Abstract: The copolar phase difference (CPD) between VV and HH polarization of X-band SAR acquisitions shows a significant dependence on the depth of fresh snow. Phase differences of 5-15 deg/10 cm fresh snow were determined at a frequency of 9.65 GHz by comparing spatial and temporal variations of snow depth (SD) with the CPD. Spatial correlations were derived from snow transect measurements during January 2012 and TanDEM-X acquisitions. Temporal correlations were derived from weather station data and TerraSAR-X acquisitions between December 2012 and April 2013. All measurements were done at a test field near the city Sodankyl{\"a}, Finland. To explain the observed CPD, a model derives birefringent properties from the microstructure of snow, which is described as aligned elliptical particles. The microscopic description is based on computer tomography observations. Different incidence angles were analyzed in consistency with the model. The temporal evolution of the CPD was linked to the temperature-gradient-driven recrystallization process. Sudden increases in the CPD indicate fresh snow. Slow decreases indicate the subsequent recrystallization process. The background signal of wet soil was considered and causes a small negative offset to the CPD. A quantitative determination of the depth of fresh snow is possible, because the specific CPD per meter of snow can be estimated. Spatial resolutions below 100x100 m are achievable with sensors such as TerraSAR-X or TanDEM-X. This paper presents a theoretical relationship between the microstructure of snow and the CPD and relates the CPD theoretically and empirically to the depth of fresh snow.

    @Article{leinssParrellaHajnsekJSTARS2014SnowHeightFromPolPhaseDifference,
    author = {Silvan Leinss and Giuseppe Parrella and Irena Hajnsek},
    title = {Snow height determination by polarimetric phase differences in {X-band} {SAR} data},
    journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
    year = {2014},
    volume = {7},
    number = {9},
    pages = {3794-3810},
    month = {Sept},
    issn = {1939-1404},
    abstract = {The copolar phase difference (CPD) between VV and HH polarization of X-band SAR acquisitions shows a significant dependence on the depth of fresh snow. Phase differences of 5-15 deg/10 cm fresh snow were determined at a frequency of 9.65 GHz by comparing spatial and temporal variations of snow depth (SD) with the CPD. Spatial correlations were derived from snow transect measurements during January 2012 and TanDEM-X acquisitions. Temporal correlations were derived from weather station data and TerraSAR-X acquisitions between December 2012 and April 2013. All measurements were done at a test field near the city Sodankyl{\"a}, Finland. To explain the observed CPD, a model derives birefringent properties from the microstructure of snow, which is described as aligned elliptical particles. The microscopic description is based on computer tomography observations. Different incidence angles were analyzed in consistency with the model. The temporal evolution of the CPD was linked to the temperature-gradient-driven recrystallization process. Sudden increases in the CPD indicate fresh snow. Slow decreases indicate the subsequent recrystallization process. The background signal of wet soil was considered and causes a small negative offset to the CPD. A quantitative determination of the depth of fresh snow is possible, because the specific CPD per meter of snow can be estimated. Spatial resolutions below 100x100 m are achievable with sensors such as TerraSAR-X or TanDEM-X. This paper presents a theoretical relationship between the microstructure of snow and the CPD and relates the CPD theoretically and empirically to the depth of fresh snow.},
    doi = {10.1109/JSTARS.2014.2323199},
    file = {:leinssParrellaHajnsekJSTARS2014SnowHeightFromPolPhaseDifference.pdf:PDF},
    keywords = {hydrological techniques;remote sensing by radar;snow;synthetic aperture radar;AD 2012 01;AD 2012 12 to 2013 04;CPD temporal evolution;Finland;HH polarization;Sodankylae city;TanDEM-X;TanDEM-X acquisitions;TerraSAR-X acquisitions;VV polarization;X-band SAR acquisitions;X-band SAR data;aligned elliptical particles;computer tomography observations;copolar phase difference;fresh snow depth;polarimetric phase difference;snow height determination;snow microstructure;subsequent recrystallization process;temperature-gradient-driven recrystallization process;weather station data;Backscatter;Scattering;Snow;Soil;Soil measurements;Synthetic aperture radar;Temperature measurement;Birefringence;TanDEM-X;TerraSAR-X;VV-HH phase difference;copolar phase difference;dry snow;fresh snow;polarimetry;snow anisotropy;snow microstructure;synthetic aperture radar},
    
    }
    


  17. Y. Luo, H. Song, R. Wang, Y. Deng, F. Zhao, and Z. Xu. Arc FMCW SAR and Applications in Ground Monitoring. IEEE Transactions on Geoscience and Remote Sensing, 52(9):5989-5998, Sept 2014. Keyword(s): GB-SAR, ground-based SAR, terrestrial SAR, Apertures, Azimuth, Doppler effect, Focusing, Rails, Synthetic aperture radar, Arc frequency-modulated continuous wave (FMCW) SAR, change detection, interferometric SAR (InSAR), synthetic aperture radar (SAR).
    Abstract: As a novel mode of ground-based synthetic aperture radar (GB-SAR), Arc frequency-modulated continuous wave (FMCW) SAR is rarely discussed in the literature up to now. Compared with the conventional rail GB-SAR system, the synthetic aperture is formed by the rotation of antennas, which can scan a wide azimuth extent. Due to its convenience and potential in SAR applications, the Institute of Electronics, Chinese Academy Sciences, carried out a series of Arc FMCW SAR experiments in March 2013, and a lot of results were obtained. In this paper, we discuss the signal processing of Arc FMCW SAR and its first results in change detection and interferometric SAR. The components of the Arc FMCW SAR system are first described, and then, we focus on its signal processing, where the signal model and its properties are investigated; two focusing algorithms are developed for different purposes. The effectiveness of the algorithms is validated by both simulation and real data experiments. We also exhibit the applications of Arc FMCW SAR in landslide detection and digital-elevation-model extraction for the first time. Results show its huge potential in ground-based applications.

    @Article{luoSongWangDengZhaoXuTGARS2014ARCSARGBSAR,
    author = {Y. Luo and H. Song and R. Wang and Y. Deng and F. Zhao and Z. Xu},
    title = {Arc FMCW SAR and Applications in Ground Monitoring},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2014},
    volume = {52},
    number = {9},
    month = {Sept},
    pages = {5989-5998},
    issn = {0196-2892},
    doi = {10.1109/TGRS.2014.2325905},
    abstract = {As a novel mode of ground-based synthetic aperture radar (GB-SAR), Arc frequency-modulated continuous wave (FMCW) SAR is rarely discussed in the literature up to now. Compared with the conventional rail GB-SAR system, the synthetic aperture is formed by the rotation of antennas, which can scan a wide azimuth extent. Due to its convenience and potential in SAR applications, the Institute of Electronics, Chinese Academy Sciences, carried out a series of Arc FMCW SAR experiments in March 2013, and a lot of results were obtained. In this paper, we discuss the signal processing of Arc FMCW SAR and its first results in change detection and interferometric SAR. The components of the Arc FMCW SAR system are first described, and then, we focus on its signal processing, where the signal model and its properties are investigated; two focusing algorithms are developed for different purposes. The effectiveness of the algorithms is validated by both simulation and real data experiments. We also exhibit the applications of Arc FMCW SAR in landslide detection and digital-elevation-model extraction for the first time. Results show its huge potential in ground-based applications.},
    keywords = {GB-SAR,ground-based SAR, terrestrial SAR,Apertures;Azimuth;Doppler effect;Focusing;Rails;Synthetic aperture radar;Arc frequency-modulated continuous wave (FMCW) SAR;change detection;interferometric SAR (InSAR);synthetic aperture radar (SAR)},
    
    }
    


  18. Jun Maeda and Kosuke Heki. Two-dimensional observations of midlatitude sporadic E irregularities with a dense GPS array in Japan. Radio Science, 49(1):28-35, 2014. Keyword(s): sporadic E, ionosphere, GPS, Global Positioning System, GNSS, Global Navigation Satellite System, GEONET, TEC, Total Electron Content.
    Abstract: We observed two-dimensional structure and time evolution of ionospheric irregularities caused by midlatitude sporadic E (Es) over Japan as positive anomalies of total electron content (TEC) by analyzing the data from the nationwide Global Positioning System (GPS) array. In this paper we report a case study of strong Es observed in the local evening of 21 May 2010, over Tokyo, Japan. In the slant TEC time series, Es showed a characteristic pulse-like enhancement of 1.5 TEC units lasting for ~10 min. We plotted these positive TEC anomalies on the subionospheric points of station-satellite pairs to study the horizontal structure of the Es irregularity. We confirmed that the irregularity existed at the height of ~106 km by comparing the data of multiple GPS satellites, which is consistent with the local ionosonde observations. The horizontal shapes of the Es irregularity showed frontal structures elongated in E-W, spanning ~150 km in length and ~30 km in width, composed of small patches. The frontal structure appears to consist of at least two parts propagating in different directions: one moved eastward by ~60 m s-1, and the other moved southwestward by ~80 m s-1. Similar TEC signatures of Es were detected by other GPS satellites, except one satellite that had line of sight in the N-S direction which dips by 40-50deg toward north, which indicates the direction of plasma transportation responsible for the Es formation. We also present a few additional observation results of strong Es irregularities.

    @Article{maedaHekiRadioScience2014IonosphereGNSSSporadicE,
    author = {Maeda, Jun and Heki, Kosuke},
    title = {Two-dimensional observations of midlatitude sporadic {E} irregularities with a dense {GPS} array in {Japan}},
    journal = {Radio Science},
    year = {2014},
    volume = {49},
    number = {1},
    pages = {28-35},
    abstract = {We observed two-dimensional structure and time evolution of ionospheric irregularities caused by midlatitude sporadic E (Es) over Japan as positive anomalies of total electron content (TEC) by analyzing the data from the nationwide Global Positioning System (GPS) array. In this paper we report a case study of strong Es observed in the local evening of 21 May 2010, over Tokyo, Japan. In the slant TEC time series, Es showed a characteristic pulse-like enhancement of 1.5 TEC units lasting for ~10 min. We plotted these positive TEC anomalies on the subionospheric points of station-satellite pairs to study the horizontal structure of the Es irregularity. We confirmed that the irregularity existed at the height of ~106 km by comparing the data of multiple GPS satellites, which is consistent with the local ionosonde observations. The horizontal shapes of the Es irregularity showed frontal structures elongated in E-W, spanning ~150 km in length and ~30 km in width, composed of small patches. The frontal structure appears to consist of at least two parts propagating in different directions: one moved eastward by ~60 m s-1, and the other moved southwestward by ~80 m s-1. Similar TEC signatures of Es were detected by other GPS satellites, except one satellite that had line of sight in the N-S direction which dips by 40-50deg toward north, which indicates the direction of plasma transportation responsible for the Es formation. We also present a few additional observation results of strong Es irregularities.},
    doi = {10.1002/2013RS005295},
    eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2013RS005295},
    file = {:maedaHekiRadioScience2014IonosphereGNSSSporadicE.pdf:PDF},
    keywords = {sporadic E, ionosphere, GPS, Global Positioning System, GNSS, Global Navigation Satellite System, GEONET, TEC, Total Electron Content},
    owner = {ofrey},
    url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2013RS005295},
    
    }
    


  19. Christophe Magnard, Max Frioud, David Small, Torsten Brehm, Helmut Essen, and Erich Meier. Processing of MEMPHIS Ka-Band Multibaseline Interferometric SAR Data: From Raw Data to Digital Surface Models. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 7(7):2927-2941, July 2014. Keyword(s): SAR Processing, SAR Interferometry, InSAR, Multibaseline Interferometry, Ka-band, Airborne SAR, Single-pass Multibaseline Interferometry, Focusing, Azimuth Focusing, Motion Compensation, data acquisition, geophysical image processing, image reconstruction, image resolution, millimetre wave radar, radar imaging, radar interferometry, radar polarimetry, radar resolution, synthetic aperture radar, DSM, MEMPHIS Ka-band multibaseline interferometric SAR data processing, SAR image resolution, azimuth focusing, cross-track multibaseline interferometric data acquisition, digital surface model, extended omega-K algorithm, interferogram generation, millimeter-wave synthetic aperture radar system, multibaseline antenna setup, observed depression angle-dependent interferometric phase error, phase unwrapping, phase-to-height conversion, reference ALS model, stepped-frequency SAR data reconstruction, Accuracy, Antennas, Azimuth, Chirp, Focusing, Motion compensation, Synthetic aperture radar, Digital surface model (DSM), Ka-band, MEMPHIS, interferometry, millimeter wave radar, multibaseline, stepped-frequency, synthetic aperture radar (SAR).
    Abstract: MEMPHIS is an experimental millimeter-wave synthetic aperture radar (SAR) system that acquires cross-track multibaseline interferometric data at high resolution in a single pass, using four receive horns. In this paper, we present the SAR system and navigation data, and propose a processing chain from the raw data input to a digital surface model (DSM) output. This processing chain includes full bandwidth reconstruction of the steppedfrequency SAR data, azimuth focusing with an Extended Omega-K algorithm, generation ofinterferograms for each available baseline, phase unwrapping using the multibaseline data, and phaseto-height conversion. The hardware and processing chain were validated through the analysis of experimental Ka-band data. The SAR image resolution was measured with point targets and found to be ~2% and 15% coarser than the theoretical value in range and azimuth, respectively. The geolocation accuracy was typically better than 0.1 m in range and 0.2 m in azimuth. Observed depression angledependent interferometric phase errors were successfully removed using a correction function derived from the InSAR data. Investigation of the interferometric phase noise showed the utility of a multibaseline antenna setup; the number of looks and filter size used for the DSM generation were also derived from this analysis. The results showed that in grassland areas, the height difference between the ~2 m-resolution InSAR DSMs and the reference ALS models was 0 +/- 0.25 m.

    @Article{magnardFrioudSmallBrehmEssenMeierJSTARS2014MemphisKaBandMBInSAR,
    author = {Christophe Magnard and Max Frioud and David Small and Torsten Brehm and Helmut Essen and Erich Meier},
    title = {Processing of MEMPHIS Ka-Band Multibaseline Interferometric SAR Data: From Raw Data to Digital Surface Models},
    journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
    year = {2014},
    volume = {7},
    number = {7},
    pages = {2927-2941},
    month = jul,
    issn = {1939-1404},
    abstract = {MEMPHIS is an experimental millimeter-wave synthetic aperture radar (SAR) system that acquires cross-track multibaseline interferometric data at high resolution in a single pass, using four receive horns. In this paper, we present the SAR system and navigation data, and propose a processing chain from the raw data input to a digital surface model (DSM) output. This processing chain includes full bandwidth reconstruction of the steppedfrequency SAR data, azimuth focusing with an Extended Omega-K algorithm, generation ofinterferograms for each available baseline, phase unwrapping using the multibaseline data, and phaseto-height conversion. The hardware and processing chain were validated through the analysis of experimental Ka-band data. The SAR image resolution was measured with point targets and found to be ~2% and 15% coarser than the theoretical value in range and azimuth, respectively. The geolocation accuracy was typically better than 0.1 m in range and 0.2 m in azimuth. Observed depression angledependent interferometric phase errors were successfully removed using a correction function derived from the InSAR data. Investigation of the interferometric phase noise showed the utility of a multibaseline antenna setup; the number of looks and filter size used for the DSM generation were also derived from this analysis. The results showed that in grassland areas, the height difference between the ~2 m-resolution InSAR DSMs and the reference ALS models was 0 +/- 0.25 m.},
    doi = {10.1109/JSTARS.2014.2315896},
    file = {:magnardFrioudSmallBrehmEssenMeierJSTARS2014MemphisKaBandMBInSAR.pdf:PDF},
    keywords = {SAR Processing, SAR Interferometry, InSAR, Multibaseline Interferometry, Ka-band, Airborne SAR, Single-pass Multibaseline Interferometry, Focusing, Azimuth Focusing, Motion Compensation, data acquisition;geophysical image processing;image reconstruction;image resolution;millimetre wave radar;radar imaging;radar interferometry;radar polarimetry;radar resolution;synthetic aperture radar;DSM;MEMPHIS Ka-band multibaseline interferometric SAR data processing;SAR image resolution;azimuth focusing;cross-track multibaseline interferometric data acquisition;digital surface model;extended omega-K algorithm;interferogram generation;millimeter-wave synthetic aperture radar system;multibaseline antenna setup;observed depression angle-dependent interferometric phase error;phase unwrapping;phase-to-height conversion;reference ALS model;stepped-frequency SAR data reconstruction;Accuracy;Antennas;Azimuth;Chirp;Focusing;Motion compensation;Synthetic aperture radar;Digital surface model (DSM);Ka-band;MEMPHIS;interferometry;millimeter wave radar;multibaseline;stepped-frequency;synthetic aperture radar (SAR)},
    owner = {ofrey},
    pdf = {../../../docs/magnardFrioudSmallBrehmEssenMeierJSTARS2014MemphisKaBandMBInSAR.pdf},
    
    }
    


  20. Pooja Mahapatra, Sami Samie Esfahany, Hans van der Marel, and Ramon F. Hanssen. On the Use of Transponders as Coherent Radar Targets for SAR Interferometry. IEEE Trans. Geosci. Remote Sens., 52(3):1869-1878, March 2014. Keyword(s): SAR Processing, Global Positioning System, geomorphology, geophysical equipment, radar interferometry, reliability, remote sensing by radar, synthetic aperture radar, terrain mapping, transponders, vegetation, ERS-2, Envisat, SAR interferometry, coherent radar targets, controlled environment, corner reflectors, double-difference transponder phase measurements, empirical precision range, field experiments, geometric variations, global positioning system, ground deformation monitoring, landslide monitoring, maintenance-related degradation, operational performance, passive devices, radar line of sight, radar transponders, reliability, transponder-InSAR observations, validation measurements, validation tests, vegetated nonurbanized areas, Corner reflector, geodesy, interferometry, measurement errors, persistent scatterer, phase measurement, quality control, synthetic aperture radar, transponder.
    Abstract: Monitoring ground deformation using SAR interferometry (InSAR) sometimes requires the introduction of coherent radar targets, especially in vegetated nonurbanized areas. Passive devices such as corner reflectors were used in such areas in the past. However, they suffer from drawbacks related to their large size and weight, conspicuousness, and loss of reliability because of geometric variations as well as material and maintenance-related degradation over several years of deployment. The viability of smaller, lighter, and less conspicuous radar transponders as an alternative is demonstrated via two field experiments: validation tests in a controlled environment, and operational performance for monitoring landslides in a heavily vegetated area. Comparison of 113 transponder-InSAR observations with independent validation measurements such as leveling and the global positioning system yields an empirical precision range of 1.8-4.6 mm, after outlier removal, for double-difference (spatial and temporal) transponder phase measurements in the radar line of sight, for Envisat and ERS-2.

    @Article{mahapatraSamieiEsfahanyVanDerMarelHanssenTGARS2014TranspondersAsCoherentTargetsForInSAR,
    author = {Mahapatra, Pooja and Samie Esfahany, Sami and van der Marel, Hans and Hanssen, Ramon F.},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {On the Use of Transponders as Coherent Radar Targets for {SAR} Interferometry},
    year = {2014},
    issn = {0196-2892},
    month = mar,
    number = {3},
    pages = {1869-1878},
    volume = {52},
    abstract = {Monitoring ground deformation using SAR interferometry (InSAR) sometimes requires the introduction of coherent radar targets, especially in vegetated nonurbanized areas. Passive devices such as corner reflectors were used in such areas in the past. However, they suffer from drawbacks related to their large size and weight, conspicuousness, and loss of reliability because of geometric variations as well as material and maintenance-related degradation over several years of deployment. The viability of smaller, lighter, and less conspicuous radar transponders as an alternative is demonstrated via two field experiments: validation tests in a controlled environment, and operational performance for monitoring landslides in a heavily vegetated area. Comparison of 113 transponder-InSAR observations with independent validation measurements such as leveling and the global positioning system yields an empirical precision range of 1.8-4.6 mm, after outlier removal, for double-difference (spatial and temporal) transponder phase measurements in the radar line of sight, for Envisat and ERS-2.},
    doi = {10.1109/TGRS.2013.2255881},
    file = {:mahapatraSamieiEsfahanyVanDerMarelHanssenTGARS2014TranspondersAsCoherentTargetsForInSAR.pdf:PDF},
    keywords = {SAR Processing, Global Positioning System;geomorphology;geophysical equipment;radar interferometry;reliability;remote sensing by radar;synthetic aperture radar;terrain mapping;transponders;vegetation;ERS-2;Envisat;SAR interferometry;coherent radar targets;controlled environment;corner reflectors;double-difference transponder phase measurements;empirical precision range;field experiments;geometric variations;global positioning system;ground deformation monitoring;landslide monitoring;maintenance-related degradation;operational performance;passive devices;radar line of sight;radar transponders;reliability;transponder-InSAR observations;validation measurements;validation tests;vegetated nonurbanized areas;Corner reflector;geodesy;interferometry;measurement errors;persistent scatterer;phase measurement;quality control;synthetic aperture radar;transponder},
    owner = {ofrey},
    pdf = {../../../docs/mahapatraSamieiEsfahanyVanDerMarelHanssenTGARS2014TranspondersAsCoherentTargetsForInSAR.pdf},
    
    }
    


  21. Oriol Monserrat, Michele Crosetto, and Guido Luzi. A review of ground-based SAR interferometry for deformation measurement. ISPRS Journal of Photogrammetry and Remote Sensing, 93:40-48, 2014. Keyword(s): SAR Processing, SAR, Interferometry, Terrestrial, Deformation, Monitoring, Review Paper, GBSAR, ground-based SAR, Differential Interferometry, DInSAR, Subsidence, Mointoring, Persistent Scatterer Interferometry, PSI.
    Abstract: Abstract This paper provides a review of ground-based SAR (GBSAR) interferometry for deformation measurement. In the first part of the paper the fundamentals of this technique are provided. Then the main data processing and analysis stages needed to estimate deformations starting from the \{GBSAR\} observations are described. This section introduces the two types of GBSAR acquisition modes, i.e., continuous and discontinuous GBSAR, and reviews the different GBSAR processing and analysis methods published in the literature. This is followed by a discussion of the specific technical aspects of GBSAR deformation measurement. A section then summarizes the pros and cons of GBSAR for deformation monitoring. The last part of the paper includes two reviews: one concerning the GBSAR systems described in the literature, including non-strictly SAR systems and a second one addresses the main GBSAR applications.

    @Article{monserratCrosettoLuziISPRS2014BGSARReview,
    author = {Oriol Monserrat and Michele Crosetto and Guido Luzi},
    title = {A review of ground-based {SAR} interferometry for deformation measurement},
    journal = {{ISPRS} Journal of Photogrammetry and Remote Sensing},
    year = {2014},
    volume = {93},
    pages = {40-48},
    issn = {0924-2716},
    abstract = {Abstract This paper provides a review of ground-based SAR (GBSAR) interferometry for deformation measurement. In the first part of the paper the fundamentals of this technique are provided. Then the main data processing and analysis stages needed to estimate deformations starting from the \{GBSAR\} observations are described. This section introduces the two types of GBSAR acquisition modes, i.e., continuous and discontinuous GBSAR, and reviews the different GBSAR processing and analysis methods published in the literature. This is followed by a discussion of the specific technical aspects of GBSAR deformation measurement. A section then summarizes the pros and cons of GBSAR for deformation monitoring. The last part of the paper includes two reviews: one concerning the GBSAR systems described in the literature, including non-strictly SAR systems and a second one addresses the main GBSAR applications.},
    doi = {http://dx.doi.org/10.1016/j.isprsjprs.2014.04.001},
    file = {:monserratCrosettoLuziISPRS2014BGSARReview.pdf:PDF},
    keywords = {SAR Processing, SAR, Interferometry,Terrestrial,Deformation,Monitoring,Review Paper, GBSAR, ground-based SAR, Differential Interferometry, DInSAR, Subsidence, Mointoring, Persistent Scatterer Interferometry, PSI},
    pdf = {../../../docs/monserratCrosettoLuziISPRS2014BGSARReview.pdf},
    url = {http://www.sciencedirect.com/science/article/pii/S0924271614000884},
    
    }
    


  22. Keith Morrison and John Bennett. Tomographic Profiling - A Technique for Multi-Incidence-Angle Retrieval of the Vertical SAR Backscattering Profiles of Biogeophysical Targets. IEEE Trans. Geosci. Remote Sens., 52(2):1350-1355, February 2014. Keyword(s): SAR Processing, SAR tomography, tomography, snow, X-band, Ku-band, geophysical image processing, image retrieval, radar imaging, remote sensing by radar, synthetic aperture radar, tomography, across-track direction, airborne application, along-track direction, biogeophysical targets, forest canopies, ground-based SAR system, ice, multiincidence-angle retrieval, satellite application, snow, subaperture elements, synthetic aperture radar imaging, tomographic profiling, vegetation, vertical SAR backscattering profiles, Array signal processing, phased arrays, radar, radar imaging, synthetic aperture radar.
    Abstract: Tomographic profiling (TP) is a new imaging technique designed to provide vertical backscatter profiles through biophysical and geophysical target volumes, such as snow, ice, vegetation, and forest canopies. Data is collected as for normal synthetic aperture radar (SAR) imaging, but with the antennas aligned along the scan or along-track direction. The real antenna provides a wide beam in the along-track direction, which is sharpened by the addition of elemental measurements across a subaperture using a SAR-like processing scheme. A novelty of the scheme is the ability to produce an image transect in which the incidence angle is constant at every point. This is accomplished by incrementally sliding the subaperture across the full aperture, and utilizing the appropriate subaperture to provide the necessary viewing geometry at each pixel. This is in contrast to the SAR case, in which the angle of incidence varies across a scene. By suitable phasing between the subaperture elements, the synthesized beam can be steered in angle within the wide angular extent of the real beam, allowing post-measurement retrieval of the backscattering properties of the scene over a continuous range of incidence angles from a single scan. In the across-track direction, a narrow real beam is required to maintain good vertical resolution and limit the size of the horizontal footprint. Example TP experimental fieldwork results are provided for a 42-cm-deep snowpack, collected with a ground-based SAR system. Although the scheme was developed for ground-based applications, its application to the airborne and satellite cases is also discussed.

    @Article{morrisonBennettTGRS2014TomoProfiling,
    author = {Morrison, Keith and Bennett, John},
    title = {Tomographic Profiling - A Technique for Multi-Incidence-Angle Retrieval of the Vertical {SAR} Backscattering Profiles of Biogeophysical Targets},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2014},
    volume = {52},
    number = {2},
    pages = {1350-1355},
    month = feb,
    issn = {0196-2892},
    abstract = {Tomographic profiling (TP) is a new imaging technique designed to provide vertical backscatter profiles through biophysical and geophysical target volumes, such as snow, ice, vegetation, and forest canopies. Data is collected as for normal synthetic aperture radar (SAR) imaging, but with the antennas aligned along the scan or along-track direction. The real antenna provides a wide beam in the along-track direction, which is sharpened by the addition of elemental measurements across a subaperture using a SAR-like processing scheme. A novelty of the scheme is the ability to produce an image transect in which the incidence angle is constant at every point. This is accomplished by incrementally sliding the subaperture across the full aperture, and utilizing the appropriate subaperture to provide the necessary viewing geometry at each pixel. This is in contrast to the SAR case, in which the angle of incidence varies across a scene. By suitable phasing between the subaperture elements, the synthesized beam can be steered in angle within the wide angular extent of the real beam, allowing post-measurement retrieval of the backscattering properties of the scene over a continuous range of incidence angles from a single scan. In the across-track direction, a narrow real beam is required to maintain good vertical resolution and limit the size of the horizontal footprint. Example TP experimental fieldwork results are provided for a 42-cm-deep snowpack, collected with a ground-based SAR system. Although the scheme was developed for ground-based applications, its application to the airborne and satellite cases is also discussed.},
    doi = {10.1109/TGRS.2013.2250508},
    file = {:morrisonBennettTGRS2014TomoProfiling.pdf:PDF},
    keywords = {SAR Processing, SAR tomography, tomography, snow, X-band, Ku-band, geophysical image processing;image retrieval;radar imaging;remote sensing by radar;synthetic aperture radar;tomography;across-track direction;airborne application;along-track direction;biogeophysical targets;forest canopies;ground-based SAR system;ice;multiincidence-angle retrieval;satellite application;snow;subaperture elements;synthetic aperture radar imaging;tomographic profiling;vegetation;vertical SAR backscattering profiles;Array signal processing;phased arrays;radar;radar imaging;synthetic aperture radar},
    pdf = {../../../docs/morrisonBennettTGRS2014TomoProfiling.pdf},
    
    }
    


  23. Mahdi Nasirian and Mohammad H. Bastani. A Novel Model for Three-Dimensional Imaging Using Interferometric ISAR in Any Curved Target Flight Path. IEEE Trans. Geosci. Remote Sens., 52(6):3236-3245, June 2014. Keyword(s): radar antennas, radar imaging, radar interferometry, radar receivers, radar tracking, radio transceivers, synthetic aperture radar, target tracking, 3D imaging, InISAR, bistatic system, curved target flight path, curvy motion, flight path form, flying object, highly nonlinear motion, interferometric ISAR, inverse synthetic aperture radar, linear trajectory, main transceiver antenna, monopulse system, nonlinear flight path, second receiver antenna, target motion, target scattering point 3D positioning, Apertures, Radar imaging, Scattering, Synthetic aperture radar, Trajectory, Vectors, Data processing, image reconstruction, interferometry, modeling, synthetic aperture radar (SAR).
    Abstract: Using a second receiver antenna close to the main transceiver antenna of inverse synthetic aperture radar (ISAR), it is possible to find 3-D positions of target scattering points. Such system is called bistatic, monopulse, or interferometric ISAR (InISAR). In the conventional model of ISAR, the unknown flying object should have a linear trajectory, and only small deviations from this trajectory can be compensated. Target motions which are highly nonlinear or curvy cannot be used in the conventional model. In this paper, we propose a new model for InISAR to process all collected data from the target, regardless of the form of the flight path. More accuracy is achieved for 3-D positioning of the target scattering points by this model because all parts of the flight path contribute in it. We will show the effectiveness of the proposed model in a nonlinear flight path by simulation.

    @Article{nasirianBastani2014,
    author = {Nasirian, Mahdi and Bastani, Mohammad H.},
    title = {A Novel Model for Three-Dimensional Imaging Using Interferometric {ISAR} in Any Curved Target Flight Path},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2014},
    volume = {52},
    number = {6},
    pages = {3236-3245},
    month = jun,
    issn = {0196-2892},
    abstract = {Using a second receiver antenna close to the main transceiver antenna of inverse synthetic aperture radar (ISAR), it is possible to find 3-D positions of target scattering points. Such system is called bistatic, monopulse, or interferometric ISAR (InISAR). In the conventional model of ISAR, the unknown flying object should have a linear trajectory, and only small deviations from this trajectory can be compensated. Target motions which are highly nonlinear or curvy cannot be used in the conventional model. In this paper, we propose a new model for InISAR to process all collected data from the target, regardless of the form of the flight path. More accuracy is achieved for 3-D positioning of the target scattering points by this model because all parts of the flight path contribute in it. We will show the effectiveness of the proposed model in a nonlinear flight path by simulation.},
    doi = {10.1109/TGRS.2013.2271875},
    file = {:nasirianBastani2014.pdf:PDF},
    keywords = {radar antennas;radar imaging;radar interferometry;radar receivers;radar tracking;radio transceivers;synthetic aperture radar;target tracking;3D imaging;InISAR;bistatic system;curved target flight path;curvy motion;flight path form;flying object;highly nonlinear motion;interferometric ISAR;inverse synthetic aperture radar;linear trajectory;main transceiver antenna;monopulse system;nonlinear flight path;second receiver antenna;target motion;target scattering point 3D positioning;Apertures;Radar imaging;Scattering;Synthetic aperture radar;Trajectory;Vectors;Data processing;image reconstruction;interferometry;modeling;synthetic aperture radar (SAR)},
    pdf = {../../../docs/nasirianBastani2014.pdf},
    
    }
    


  24. E Nikolaeva, TR Walter, Manoochehr Shirzaei, and J Zschau. Landslide observation and volume estimation in central Georgia based on L-band InSAR. Natural Hazards and Earth System Sciences, 14(3):675-688, 2014.
    @Article{Nikolaeva2014,
    author = {Nikolaeva, E and Walter, TR and Shirzaei, Manoochehr and Zschau, J},
    title = {Landslide observation and volume estimation in central Georgia based on L-band InSAR},
    year = {2014},
    volume = {14},
    number = {3},
    pages = {675--688},
    journal = {Natural Hazards and Earth System Sciences},
    owner = {ofrey},
    publisher = {Copernicus GmbH},
    
    }
    


  25. Octavio Ponce, Pau Prats-Iraola, Muriel Pinheiro, Marc Rodriguez-Cassola, Rolf Scheiber, Andreas Reigber, and Alberto Moreira. Fully Polarimetric High-Resolution 3-D Imaging With Circular SAR at L-Band. IEEE Trans. Geosci. Remote Sens., 52(6):3074-3090, June 2014. Keyword(s): SAR Processing, Circular SAR, Time-Domain Back-Projection, TDBP, MoComp, Motion Compensation, Bandwidth, Image resolution, Imaging, L-band, Synthetic aperture radar, Trajectory, Autofocus, circular synthetic aperture radar (CSAR), fast factorized back-projection, FFBP, graphics processing unit (GPU), high-resolution SAR, polarimetry, synthetic aperture radar (SAR), tomography, SAR Tomography.
    Abstract: This paper presents the first fully polarimetric highresolution circular synthetic aperture radar (CSAR) images at L-band (1.3 GHz). The circular data were acquired in 2008 by the Experimental SAR (E-SAR) airborne system of the German Aerospace Center (DLR) over the airport of Kaufbeuren, Germany. The obtained images resulting from the coherent integration of the whole circular flight are investigated and discussed in terms of two of the main CSAR properties, namely, the theoretical subwavelength resolution in the horizontal plane (x, y) and the 3-D imaging capabilities. The 3-D imaging capabilities are of special interest due to the penetration of L-band in vegetated areas. These results were compared with images processed by the incoherent addition of the full synthetic aperture. The coherent approach showed a better performance since scatterers are focused at their maximum resolution. Due to the nonlinearity of the tracks and the high-computational burden, an efficient fast factorized back-projection (FFBP) has been developed. Unlike frequencydomain processors, it accommodates azimuthal variances and topography changes. Limits and considerations of the proposed algorithm are described and discussed. To further accelerate this process, the FFBP was also implemented in a graphics processing unit (GPU). Processing performance has been assessed with the direct BP (DBP) as a reference, obtaining speedup factors up to 1800. Residual motion errors have been estimated with a new frequency-based autofocus approach for CSAR configurations based on low signal-to-clutter ratio (SCR) isotropic scatterers. High-resolution images of man-made and distributed scatterers have been analyzed and compared with a stripmap SAR, both concerning anisotropic and isotropic-like scatterers. Results include a single-channel tomogram of a Luneburg lens and a fully polarimetric tomogram of a tree.

    @Article{poncePratsIraolaPinheiroRodriguezScheiberMoreiraTGRS2014CircularTomoSAR,
    author = {Ponce, Octavio and Prats-Iraola, Pau and Pinheiro, Muriel and Rodriguez-Cassola, Marc and Scheiber, Rolf and Reigber, Andreas and Moreira, Alberto},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Fully Polarimetric High-Resolution {3-D} Imaging With Circular {SAR} at {L}-Band},
    year = {2014},
    issn = {0196-2892},
    month = {jun},
    number = {6},
    pages = {3074--3090},
    volume = {52},
    abstract = {This paper presents the first fully polarimetric highresolution circular synthetic aperture radar (CSAR) images at L-band (1.3 GHz). The circular data were acquired in 2008 by the Experimental SAR (E-SAR) airborne system of the German Aerospace Center (DLR) over the airport of Kaufbeuren, Germany. The obtained images resulting from the coherent integration of the whole circular flight are investigated and discussed in terms of two of the main CSAR properties, namely, the theoretical subwavelength resolution in the horizontal plane (x, y) and the 3-D imaging capabilities. The 3-D imaging capabilities are of special interest due to the penetration of L-band in vegetated areas. These results were compared with images processed by the incoherent addition of the full synthetic aperture. The coherent approach showed a better performance since scatterers are focused at their maximum resolution. Due to the nonlinearity of the tracks and the high-computational burden, an efficient fast factorized back-projection (FFBP) has been developed. Unlike frequencydomain processors, it accommodates azimuthal variances and topography changes. Limits and considerations of the proposed algorithm are described and discussed. To further accelerate this process, the FFBP was also implemented in a graphics processing unit (GPU). Processing performance has been assessed with the direct BP (DBP) as a reference, obtaining speedup factors up to 1800. Residual motion errors have been estimated with a new frequency-based autofocus approach for CSAR configurations based on low signal-to-clutter ratio (SCR) isotropic scatterers. High-resolution images of man-made and distributed scatterers have been analyzed and compared with a stripmap SAR, both concerning anisotropic and isotropic-like scatterers. Results include a single-channel tomogram of a Luneburg lens and a fully polarimetric tomogram of a tree.},
    doi = {10.1109/TGRS.2013.2269194},
    file = {:poncePratsIraolaPinheiroRodriguezScheiberMoreiraTGRS2013.pdf:PDF},
    keywords = {SAR Processing, Circular SAR, Time-Domain Back-Projection, TDBP, MoComp, Motion Compensation;Bandwidth;Image resolution;Imaging;L-band;Synthetic aperture radar;Trajectory;Autofocus;circular synthetic aperture radar (CSAR);fast factorized back-projection, FFBP;graphics processing unit (GPU);high-resolution SAR;polarimetry;synthetic aperture radar (SAR);tomography, SAR Tomography},
    pdf = {../../../docs/poncePratsIraolaPinheiroRodriguezScheiberMoreiraTGRS2013.pdf},
    publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
    
    }
    


  26. O. Ponce, P. Prats-Iraola, R. Scheiber, A. Reigber, A. Moreira, and E. Aguilera. Polarimetric 3-D Reconstruction From Multicircular SAR at P-Band. IEEE_J_GRSL, 11(4):803-807, April 2014. Keyword(s): airborne radar, array signal processing, calibration, compressed sensing, image reconstruction, image resolution, optical focusing, radar imaging, radar polarimetry, radar resolution, singular value decomposition, synthetic aperture radar, 2D image stacking, 3D cone-shaped sidelobe suppression, 3D reconstruction polarimetry, BF, CS, DLR, FFBP, German Aerospace Center F-SAR system, LOS, P-band, SVD, Vordemwald Switzerland, beamforming, circular flight, complex reflectivity solution, compressive sensing, constant phase offset estimation, fast-factorized back projection, line of sight, multicircular synthetic aperture radar, phase calibration method, polarimetric MCSAR airborne experiment, radar resolution, singular value decomposition, Apertures, Calibration, Focusing, Image resolution, Remote sensing, Synthetic aperture radar, Circular synthetic aperture radar (SAR) (CSAR), compressive sensing (CS), phase calibration, polarimetric SAR (PolSAR), singular value decomposition (SVD), tomography.
    @Article{poncePratsScheiberReigberMoreiraAquileraGRSLTGRS2016CircularSARTOMOPBand,
    author = {O. Ponce and P. Prats-Iraola and R. Scheiber and A. Reigber and A. Moreira and E. Aguilera},
    title = {Polarimetric {3-D} Reconstruction From Multicircular {SAR} at P-Band},
    journal = IEEE_J_GRSL,
    year = {2014},
    volume = {11},
    number = {4},
    month = apr,
    pages = {803--807},
    issn = {1545-598X},
    doi = {10.1109/LGRS.2013.2279236},
    keywords = {airborne radar, array signal processing, calibration, compressed sensing, image reconstruction, image resolution, optical focusing, radar imaging, radar polarimetry, radar resolution, singular value decomposition, synthetic aperture radar, 2D image stacking, 3D cone-shaped sidelobe suppression, 3D reconstruction polarimetry, BF, CS, DLR, FFBP, German Aerospace Center F-SAR system, LOS, P-band, SVD, Vordemwald Switzerland, beamforming, circular flight, complex reflectivity solution, compressive sensing, constant phase offset estimation, fast-factorized back projection, line of sight, multicircular synthetic aperture radar, phase calibration method, polarimetric MCSAR airborne experiment, radar resolution, singular value decomposition, Apertures, Calibration, Focusing, Image resolution, Remote sensing, Synthetic aperture radar, Circular synthetic aperture radar (SAR) (CSAR), compressive sensing (CS), phase calibration, polarimetric SAR (PolSAR), singular value decomposition (SVD), tomography},
    owner = {ofrey},
    
    }
    


  27. Pau Prats-Iraola, Marc Rodriguez-Cassola, Francseco De Zan, Pau L�pez-Dekker, Rolf Scheiber, and Andreas Reigber. Efficient Evaluation of Fourier-Based SAR Focusing Kernels. IEEE Geoscience and Remote Sensing Letters, 11(9):1489-1493, Sep. 2014. Keyword(s): airborne radar, image resolution, image sensors, numerical analysis, optical focusing, optical transfer function, radar imaging, spaceborne radar, synthetic aperture radar, transient response, geometry, transfer function, airborne SAR sensor, spaceborne SAR sensor, IRF, 2D point target spectrum simulation, numerical analysis, bistatic SAR image resolution, spaceborne SAR image resolution, compact analytic expression, hyperbolic range history, residual phase error, focused impulse response function, SAR image formation, synthetic aperture radar image formation, Fourier-based SAR focusing kernel, Kernel, Synthetic aperture radar, Focusing, Azimuth, Transfer functions, Geometry, Spaceborne radar, SAR processing, SAR simulation, SAR spectrum, spotlight SAR, synthetic aperture radar (SAR), SAR processing, SAR simulation, SAR spectrum, spotlight SAR, synthetic aperture radar (SAR).
    Abstract: This letter addresses the efficient evaluation of Fourier-based kernels for synthetic aperture radar (SAR) image formation. The goal is to evaluate the quality of the focused impulse response function and the residual phase errors of the kernel without having to implement the processor itself nor perform a costly point-target simulation followed by the processing. The proposed methodology is convenient for situations where the assumption of a hyperbolic range history does not hold anymore, and hence, a compact analytic expression of the point target spectrum is not available. Examples where the hyperbolic range history does not apply include very high resolution spaceborne SAR imaging or bistatic SAR imaging. The approach first numerically computes the 2-D spectrum of a point target and then uses the transfer function of the focusing kernel to match it. The spectral support is then computed to adapt the spectrum to the output imaging geometry, so that the impulse response function (IRF) is finally obtained. The proposed approach is valid under the assumption of a large time-bandwidth product, as is usually the case for current air- and spaceborne SAR sensors. The methodology is validated by comparing the matched IRFs with the ones obtained using point-target simulations.

    @Article{pratsRodriguezDeZanLopezDekkerScheiberReigberGRSL2014EfficientEvaluationOfFourierBasedFocusingKernels,
    author = {Pau {Prats-Iraola} and Marc {Rodriguez-Cassola} and Francseco {De Zan} and Pau {L�pez-Dekker} and Rolf {Scheiber} and Andreas {Reigber}},
    title = {Efficient Evaluation of Fourier-Based SAR Focusing Kernels},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    year = {2014},
    volume = {11},
    number = {9},
    pages = {1489-1493},
    month = {Sep.},
    issn = {1558-0571},
    abstract = {This letter addresses the efficient evaluation of Fourier-based kernels for synthetic aperture radar (SAR) image formation. The goal is to evaluate the quality of the focused impulse response function and the residual phase errors of the kernel without having to implement the processor itself nor perform a costly point-target simulation followed by the processing. The proposed methodology is convenient for situations where the assumption of a hyperbolic range history does not hold anymore, and hence, a compact analytic expression of the point target spectrum is not available. Examples where the hyperbolic range history does not apply include very high resolution spaceborne SAR imaging or bistatic SAR imaging. The approach first numerically computes the 2-D spectrum of a point target and then uses the transfer function of the focusing kernel to match it. The spectral support is then computed to adapt the spectrum to the output imaging geometry, so that the impulse response function (IRF) is finally obtained. The proposed approach is valid under the assumption of a large time-bandwidth product, as is usually the case for current air- and spaceborne SAR sensors. The methodology is validated by comparing the matched IRFs with the ones obtained using point-target simulations.},
    doi = {10.1109/LGRS.2013.2296371},
    keywords = {airborne radar;image resolution;image sensors;numerical analysis;optical focusing;optical transfer function;radar imaging;spaceborne radar;synthetic aperture radar;transient response;geometry;transfer function;airborne SAR sensor;spaceborne SAR sensor;IRF;2D point target spectrum simulation;numerical analysis;bistatic SAR image resolution;spaceborne SAR image resolution;compact analytic expression;hyperbolic range history;residual phase error;focused impulse response function;SAR image formation;synthetic aperture radar image formation;Fourier-based SAR focusing kernel;Kernel;Synthetic aperture radar;Focusing;Azimuth;Transfer functions;Geometry;Spaceborne radar;SAR processing;SAR simulation;SAR spectrum;spotlight SAR;synthetic aperture radar (SAR);SAR processing;SAR simulation;SAR spectrum;spotlight SAR;synthetic aperture radar (SAR)},
    owner = {ofrey},
    
    }
    


  28. Pau Prats-Iraola, Rolf Scheiber, Marc Rodriguez-Cassola, J. Mittermayer, S. Wollstadt, F. De Zan, B. Brautigam, M. Schwerdt, Andreas Reigber, and Alberto Moreira. On the Processing of Very High Resolution Spaceborne SAR Data. IEEE Trans. Geosci. Remote Sens., 52(10):6003-6016, October 2014. Keyword(s): SAR Processing, Spaceborne SAR, SAR Focusing, Azimuth focusing, radar antennas, remote sensing by radar, synthetic aperture radar, TerraSAR-X, bandwidth 300 MHz, chirp signal, complete focusing methodology, decimeter range, electronically steered antennas, satellite motion, synthetic aperture radar, troposphere effect, very high resolution spaceborne SAR data, Azimuth, Bandwidth, Geometry, Orbits, Satellites, Synthetic aperture radar, Terrestrial atmosphere, SAR processing, spotlight SAR, stop-and-go approximation, synthetic aperture radar (SAR), troposphere.
    Abstract: This paper addresses several important aspects that need to be considered for the processing of spaceborne synthetic aperture radar (SAR) data with resolutions in the decimeter range. In particular, it will be shown how the motion of the satellite during the transmission/reception of the chirp signal and the effect of the troposphere deteriorate the impulse response function if not properly considered. Further aspects that have been investigated include the curved orbit, the array pattern for electronically steered antennas, and several considerations within the processing itself. For each aspect, a solution is proposed, and the complete focusing methodology is expounded and validated using simulated point targets and staring spotlight data acquired by TerraSAR-X with 16-cm azimuth resolution and 300-MHz range bandwidth.

    @Article{pratsScheiberRodriguezCassolaMittermayerWollstadtDeZanBrautigamSchwerdtReigberMoreiraTGRS2014,
    author = {Prats-Iraola, Pau and Scheiber, Rolf and Rodriguez-Cassola, Marc and Mittermayer, J. and Wollstadt, S. and De Zan, F. and Brautigam, B. and Schwerdt, M. and Reigber, Andreas and Moreira, Alberto},
    title = {On the Processing of Very High Resolution Spaceborne {SAR} Data},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2014},
    volume = {52},
    number = {10},
    pages = {6003-6016},
    month = oct,
    issn = {0196-2892},
    abstract = {This paper addresses several important aspects that need to be considered for the processing of spaceborne synthetic aperture radar (SAR) data with resolutions in the decimeter range. In particular, it will be shown how the motion of the satellite during the transmission/reception of the chirp signal and the effect of the troposphere deteriorate the impulse response function if not properly considered. Further aspects that have been investigated include the curved orbit, the array pattern for electronically steered antennas, and several considerations within the processing itself. For each aspect, a solution is proposed, and the complete focusing methodology is expounded and validated using simulated point targets and staring spotlight data acquired by TerraSAR-X with 16-cm azimuth resolution and 300-MHz range bandwidth.},
    doi = {10.1109/TGRS.2013.2294353},
    file = {:pratsScheiberRodriguezCassolaMittermayerWollstadtDeZanBrautigamSchwerdtReigberMoreiraTGRS2014.pdf:PDF},
    keywords = {SAR Processing, Spaceborne SAR, SAR Focusing, Azimuth focusing, radar antennas;remote sensing by radar;synthetic aperture radar;TerraSAR-X;bandwidth 300 MHz;chirp signal;complete focusing methodology;decimeter range;electronically steered antennas;satellite motion;synthetic aperture radar;troposphere effect;very high resolution spaceborne SAR data;Azimuth;Bandwidth;Geometry;Orbits;Satellites;Synthetic aperture radar;Terrestrial atmosphere;SAR processing;spotlight SAR;stop-and-go approximation;synthetic aperture radar (SAR);troposphere},
    pdf = {../../../docs/pratsScheiberRodriguezCassolaMittermayerWollstadtDeZanBrautigamSchwerdtReigberMoreiraTGRS2014.pdf},
    
    }
    


  29. Craig Stringham and David G. Long. GPU Processing for UAS-Based LFM-CW Stripmap SAR. Photogrammetric Engineering & Remote Sensing, 80(12):1107-1115, 2014. Keyword(s): SAR Processing, Azimuth Focusing, Time-domain back-projection, TDBP, SAR focusing, GPU, GPU-based parallelized TDBP, graphics processing units, motion compensation, parallel processing, radar signal processing, synthetic aperture radar, 3D motion compensation, GPU based backprojection processing, NVIDIA CUDA GPU computing framework, SAR processing scheme, agile SAR platforms, parallelized backprojection processing, time domain backprojection processing, Azimuth, Focusing, Graphics processing units, Remote sensing, Synthetic aperture radar, Time-domain analysis, Azimuth focusing, CARSAR, CUDA, GPU, Parallelization, SAR imaging.
    Abstract: Unmanned air systems (UAS) provide an excellent platform for synthetic aperture radar (SAR), enabling surveillance and research over areas too difficult, dangerous, or costly to reach using manned aircraft. However, the nimble nature of the small UAS makes them more susceptible to external forces, thus requiring significant motion compensation in order for SAR images to focus properly. SAR backprojection has been found to improve the focusing of low-altitude stripmap SAR images compared to frequency domain algorithms. In this paper we describe the development and implementation of SAR backprojection appropriate for UAS based stripmap SAR that utilizes the unique architecture of a GPU in order to produce high-quality imagery in real-time.

    @Article{stringhamLongPERS2014GPUbasedTDBP,
    author = {Stringham, Craig and Long, David G.},
    title = {{GPU} Processing for {UAS}-Based {LFM-CW} Stripmap {SAR}},
    journal = {Photogrammetric Engineering \& Remote Sensing},
    year = {2014},
    volume = {80},
    number = {12},
    pages = {1107--1115},
    abstract = {Unmanned air systems (UAS) provide an excellent platform for synthetic aperture radar (SAR), enabling surveillance and research over areas too difficult, dangerous, or costly to reach using manned aircraft. However, the nimble nature of the small UAS makes them more susceptible to external forces, thus requiring significant motion compensation in order for SAR images to focus properly. SAR backprojection has been found to improve the focusing of low-altitude stripmap SAR images compared to frequency domain algorithms. In this paper we describe the development and implementation of SAR backprojection appropriate for UAS based stripmap SAR that utilizes the unique architecture of a GPU in order to produce high-quality imagery in real-time.},
    doi = {10.14358/PERS.80.12.1107},
    file = {:stringhamLongPERS2014GPUbasedTDBP.pdf:PDF},
    keywords = {SAR Processing, Azimuth Focusing, Time-domain back-projection, TDBP, SAR focusing, GPU, GPU-based parallelized TDBP, graphics processing units;motion compensation;parallel processing;radar signal processing;synthetic aperture radar; 3D motion compensation;GPU based backprojection processing;NVIDIA CUDA GPU computing framework; SAR processing scheme;agile SAR platforms; parallelized backprojection processing; time domain backprojection processing;Azimuth;Focusing;Graphics processing units; Remote sensing;Synthetic aperture radar;Time-domain analysis; Azimuth focusing;CARSAR;CUDA;GPU; Parallelization;SAR imaging},
    pdf = {../../../docs/stringhamLongPERS2014GPUbasedTDBP.pdf},
    publisher = {American Society for Photogrammetry and Remote Sensing},
    url = {http://www.asprs.org/a/publications/pers/2014journals/PERS_December_2014/HTML/files/assets/common/downloads/PE&RS%20December%202014.pdf},
    
    }
    


  30. Jan Torgrimsson, Patrik Dammert, Hans Hellsten, and Lars M. H. Ulander. Factorized Geometrical Autofocus for Synthetic Aperture Radar Processing. IEEE Trans. Geosci. Remote Sens., 52(10):6674-6687, October 2014. Keyword(s): SAR Processing, Fast-Factorized Back-Projection, FFBP, Time-Domain Back-Projection, TDBP, Airborne SAR, CARABAS Autofocus, SAR Autofocus, Geometrical Autofocus, radar imaging, radar tracking, synthetic aperture radar, ultra wideband radar, FGA algorithm, coherent all radio band system II data set, constrained problem, factorized geometrical autofocus algorithm, fast factorized back-projection chain, gain 3 dB, intensity correlation, object function, peak-to-sidelobe ratio measurement, radar imaging, residual space variant range cell migration, ultrawideband synthetic aperture radar processing, Apertures, Electronics packaging, Geometry, Radar tracking, Synthetic aperture radar, Transforms, Autofocus, back-projection, phase gradient algorithm (PGA), synthetic aperture radar (SAR).
    Abstract: This paper describes a factorized geometrical autofocus (FGA) algorithm, specifically suitable for ultrawideband synthetic aperture radar. The strategy is integrated in a fast factorized back-projection chain and relies on varying track parameters step by step to obtain a sharp image; focus measures are provided by an object function (intensity correlation). The FGA algorithm has been successfully applied on synthetic and real (Coherent All RAdio BAnd System II) data sets, i.e., with false track parameters introduced prior to processing, to set up constrained problems involving one geometrical quantity. Resolution (3 dB in azimuth and slant range) and peak-to-sidelobe ratio measurements in FGA images are comparable with reference results (within a few percent and tenths of a decibel), demonstrating the capacity to compensate for residual space variant range cell migration. The FGA algorithm is finally also benchmarked (visually) against the phase gradient algorithm to emphasize the advantage of a geometrical autofocus approach.

    @Article{torgrimssonDammertHellstenUlanderFFBPAutofocusTGRS2014,
    author = {Torgrimsson, Jan and Dammert, Patrik and Hellsten, Hans and Ulander, Lars M. H.},
    title = {Factorized Geometrical Autofocus for Synthetic Aperture Radar Processing},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2014},
    volume = {52},
    number = {10},
    pages = {6674-6687},
    month = oct,
    issn = {0196-2892},
    abstract = {This paper describes a factorized geometrical autofocus (FGA) algorithm, specifically suitable for ultrawideband synthetic aperture radar. The strategy is integrated in a fast factorized back-projection chain and relies on varying track parameters step by step to obtain a sharp image; focus measures are provided by an object function (intensity correlation). The FGA algorithm has been successfully applied on synthetic and real (Coherent All RAdio BAnd System II) data sets, i.e., with false track parameters introduced prior to processing, to set up constrained problems involving one geometrical quantity. Resolution (3 dB in azimuth and slant range) and peak-to-sidelobe ratio measurements in FGA images are comparable with reference results (within a few percent and tenths of a decibel), demonstrating the capacity to compensate for residual space variant range cell migration. The FGA algorithm is finally also benchmarked (visually) against the phase gradient algorithm to emphasize the advantage of a geometrical autofocus approach.},
    doi = {10.1109/TGRS.2014.2300347},
    file = {:torgrimssonDammertHellstenUlanderFFBPAutofocusTGRS2014.pdf:PDF},
    keywords = {SAR Processing, Fast-Factorized Back-Projection, FFBP, Time-Domain Back-Projection, TDBP, Airborne SAR, CARABAS Autofocus, SAR Autofocus, Geometrical Autofocus, radar imaging;radar tracking;synthetic aperture radar;ultra wideband radar;FGA algorithm;coherent all radio band system II data set;constrained problem;factorized geometrical autofocus algorithm;fast factorized back-projection chain;gain 3 dB;intensity correlation;object function;peak-to-sidelobe ratio measurement;radar imaging;residual space variant range cell migration;ultrawideband synthetic aperture radar processing;Apertures;Electronics packaging;Geometry;Radar tracking;Synthetic aperture radar;Transforms;Autofocus;back-projection;phase gradient algorithm (PGA);synthetic aperture radar (SAR)},
    pdf = {../../../docs/torgrimssonDammertHellstenUlanderFFBPAutofocusTGRS2014.pdf},
    
    }
    


  31. Viet Thuy Vu, Thomas K. Sjogren, and Mats I. Pettersson. Two-Dimensional Spectrum for BiSAR Derivation Based on Lagrange Inversion Theorem. IEEE Geosci. Remote Sens. Lett., 11(7):1210-1214, July 2014. Keyword(s): SAR Processing, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, Bistatic SAR, Bistatic Fast-Factorized Back-Projection, BiFFBP, Fourier transforms, inverse problems, synthetic aperture radar, BiSAR derivation, Fourier transform, Lagrange inversion theorem, bistatic synthetic aperture radar, stationary phase, two-dimensional spectrum, Apertures, Azimuth, Focusing, Frequency-domain analysis, Remote sensing, Synthetic aperture radar, Transmitters, Bistatic synthetic aperture radar (BiSAR), LORA, Lagrange inversion theorem, two-dimensional spectrum.
    Abstract: A 2-D spectrum for bistatic synthetic aperture radar is derived in this letter. The derivation is based on the commonly used mathematic principles such as the method of stationary phase and the Fourier transform and the Lagrange inversion theorem in order to find the point of stationary phase in the method of stationary phase. Using the Lagrange inversion theorem allows minimizing the initial assumptions or the initial approximations. The derived 2-D spectrum is compared with the commonly used 2-D spectrum to verify it and illustrate its accuracy.

    @Article{vuSjogrenPetterssonGRSL2014,
    Title = {Two-Dimensional Spectrum for {BiSAR} Derivation Based on {Lagrange} Inversion Theorem},
    Author = {Vu, Viet Thuy and Sjogren, Thomas K. and Pettersson, Mats I.},
    Doi = {10.1109/LGRS.2013.2289735},
    ISSN = {1545-598X},
    Month = {July},
    Number = {7},
    Pages = {1210-1214},
    Volume = {11},
    Year = {2014},
    Abstract = {A 2-D spectrum for bistatic synthetic aperture radar is derived in this letter. The derivation is based on the commonly used mathematic principles such as the method of stationary phase and the Fourier transform and the Lagrange inversion theorem in order to find the point of stationary phase in the method of stationary phase. Using the Lagrange inversion theorem allows minimizing the initial assumptions or the initial approximations. The derived 2-D spectrum is compared with the commonly used 2-D spectrum to verify it and illustrate its accuracy.},
    Journal = {IEEE Geosci. Remote Sens. Lett.},
    Keywords = {SAR Processing, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, Bistatic SAR, Bistatic Fast-Factorized Back-Projection, BiFFBP, Fourier transforms;inverse problems;synthetic aperture radar;BiSAR derivation;Fourier transform;Lagrange inversion theorem;bistatic synthetic aperture radar;stationary phase;two-dimensional spectrum;Apertures;Azimuth;Focusing;Frequency-domain analysis;Remote sensing;Synthetic aperture radar;Transmitters;Bistatic synthetic aperture radar (BiSAR);LORA;Lagrange inversion theorem;two-dimensional spectrum} 
    }
    


  32. TR Walter, Manoochehr Shirzaei, A Manconi, G Solaro, A Pepe, M Manzo, and E Sansosti. Possible coupling of Campi Flegrei and Vesuvius as revealed by InSAR time series, correlation analysis and time dependent modeling. Journal of Volcanology and Geothermal Research, 280:104-110, 2014.
    @Article{Walter2014,
    author = {Walter, TR and Shirzaei, Manoochehr and Manconi, A and Solaro, G and Pepe, A and Manzo, M and Sansosti, E},
    title = {Possible coupling of Campi Flegrei and Vesuvius as revealed by InSAR time series, correlation analysis and time dependent modeling},
    year = {2014},
    volume = {280},
    pages = {104--110},
    journal = {Journal of Volcanology and Geothermal Research},
    owner = {ofrey},
    publisher = {Elsevier},
    
    }
    


  33. Yuanyuan Wang, Xiao Xiang Zhu, and Richard Bamler. An efficient tomographic inversion approach for urban mapping using meter resolution SAR image stacks. IEEE Geoscience and Remote Sensing Letters, 11(7):1250-1254, 2014.
    @Article{wangZhuBamlerGRSL2014,
    author = {Wang, Yuanyuan and Zhu, Xiao Xiang and Bamler, Richard},
    title = {An efficient tomographic inversion approach for urban mapping using meter resolution {SAR} image stacks},
    year = {2014},
    volume = {11},
    number = {7},
    pages = {1250-1254},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    owner = {ofrey},
    publisher = {IEEE},
    
    }
    


  34. Francesco De Zan, A. Parizzi, Pau Prats-Iraola, and Paco López-Dekker. A SAR Interferometric Model for Soil Moisture. IEEE_J_GRS, 52(1):418-425, January 2014. Keyword(s): dielectric properties, hydrological techniques, radar interferometry, remote sensing by radar, soil, synthetic aperture radar, Born approximation, L-band airborne SAR data, SAR interferometric model, coherence magnitudes, complex interferometric coherences, dielectric properties, geometrical properties, interferogram triplets, phase consistency, plane waves, quantitatively synthetic aperture radar interferometric observables, scattering models, soil moisture, tomography, vertical complex wavenumbers, Coherence, L-band, Moisture, Soil moisture, Synthetic aperture radar, Coherence, soil moisture, synthetic aperture radar (SAR) interferometry.
    Abstract: In this paper, a new autofocus algorithm is presented for back-projection (BP) image formation of synthetic aperture radar (SAR) imaging. The approach is based on maximizing a cost function obtained by prominent points in different sub-apertures of constructed SAR image by varying the flight trajectory parameters. While image-quality-based autofocus approach together with BP algorithm can be computationally intensive, we use approximations that allow optimal corrections to be derived. The approach is applicable for focusing different signal processing algorithms by obtaining modified flight trajectory parameters. Different examples demonstrate the effectiveness of the new autofocus approach applied to the frequency modulated continuous wave mode SAR dataset.

    @Article{Zan2014,
    author = {Francesco De Zan and A. Parizzi and Pau Prats-Iraola and Paco L{\'o}pez-Dekker},
    title = {A {SAR} Interferometric Model for Soil Moisture},
    year = {2014},
    volume = {52},
    number = {1},
    month = jan,
    pages = {418--425},
    issn = {0196-2892},
    doi = {10.1109/TGRS.2013.2241069},
    abstract = {In this paper, a new autofocus algorithm is presented for back-projection (BP) image formation of synthetic aperture radar (SAR) imaging. The approach is based on maximizing a cost function obtained by prominent points in different sub-apertures of constructed SAR image by varying the flight trajectory parameters. While image-quality-based autofocus approach together with BP algorithm can be computationally intensive, we use approximations that allow optimal corrections to be derived. The approach is applicable for focusing different signal processing algorithms by obtaining modified flight trajectory parameters. Different examples demonstrate the effectiveness of the new autofocus approach applied to the frequency modulated continuous wave mode SAR dataset.},
    journal = IEEE_J_GRS,
    keywords = {dielectric properties, hydrological techniques, radar interferometry, remote sensing by radar, soil, synthetic aperture radar, Born approximation, L-band airborne SAR data, SAR interferometric model, coherence magnitudes, complex interferometric coherences, dielectric properties, geometrical properties, interferogram triplets, phase consistency, plane waves, quantitatively synthetic aperture radar interferometric observables, scattering models, soil moisture, tomography, vertical complex wavenumbers, Coherence, L-band, Moisture, Soil moisture, Synthetic aperture radar, Coherence, soil moisture, synthetic aperture radar (SAR) interferometry},
    owner = {ofrey},
    
    }
    


  35. Lei Zhang, Hao-lin Li, Zhi-Jun Qiao, and Zhi-wei Xu. A Fast BP Algorithm With Wavenumber Spectrum Fusion for High-Resolution Spotlight SAR Imaging. IEEE Geosci. Remote Sens. Lett., 11(9):1460-1464, September 2014. Keyword(s): SAR Processing, Fast-Factorized Back-Projection, FFBP, Fast Backprojection, fast Fourier transforms, image fusion, image resolution, interpolation, radar imaging, synthetic aperture radar, transient response, AFBP algorithm, FFBP algorithm, SA fusion, UPC system, WN spectrum domain, accelerated fast backprojection algorithm, fast Fourier transform, fast factorization backprojection algorithm, high-resolution spotlight SAR imaging, image-domain interpolation, impulse response function, interpolation-based fusion, subaperture fusion, synthetic aperture radar, unified polar coordinate system, wavenumber spectrum fusion, Apertures, Azimuth, Image resolution, Imaging, Interpolation, Signal processing algorithms, Synthetic aperture radar, Accelerated fast BP (AFBP), fast backprojection (FBP), fast factorized backprojection (FFBP).
    Abstract: This letter presents the accelerated fast backprojection (AFBP) algorithm for high-resolution spotlight synthetic aperture radar (SAR) imaging. In conventional fast backprojection (FBP) algorithms, image-domain interpolation is employed in the subaperture (SA) fusion. However, in AFBP, by using a unified polar coordinate (UPC) system, the interpolation-based fusion is substituted by fusing the SA spectra in the wavenumber (WN) spectrum domain. The WN-domain SA fusion is efficiently implemented by fast Fourier transform and circular shifting. In this letter, an accurate impulse response function and the WN spectrum expression of the backprojected image in the UPC are explicitly derived, and furthermore, the implementations of AFBP are investigated in detail. Compared with conventional FBP algorithms, the AFBP can precisely focus on high-resolution SAR data with dramatically improved efficiency. Both simulation and real-measured data experiments validate the superiorities of AFBP by comparing it with the fast factorization backprojection (FFBP) algorithm.

    @Article{zhangLiQiaoXuTGRS2014FastBackProjection,
    author = {Lei Zhang and Hao-lin Li and Zhi-Jun Qiao and Zhi-wei Xu},
    title = {A Fast {BP} Algorithm With Wavenumber Spectrum Fusion for High-Resolution Spotlight {SAR} Imaging},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2014},
    volume = {11},
    number = {9},
    pages = {1460-1464},
    month = sep,
    issn = {1545-598X},
    abstract = {This letter presents the accelerated fast backprojection (AFBP) algorithm for high-resolution spotlight synthetic aperture radar (SAR) imaging. In conventional fast backprojection (FBP) algorithms, image-domain interpolation is employed in the subaperture (SA) fusion. However, in AFBP, by using a unified polar coordinate (UPC) system, the interpolation-based fusion is substituted by fusing the SA spectra in the wavenumber (WN) spectrum domain. The WN-domain SA fusion is efficiently implemented by fast Fourier transform and circular shifting. In this letter, an accurate impulse response function and the WN spectrum expression of the backprojected image in the UPC are explicitly derived, and furthermore, the implementations of AFBP are investigated in detail. Compared with conventional FBP algorithms, the AFBP can precisely focus on high-resolution SAR data with dramatically improved efficiency. Both simulation and real-measured data experiments validate the superiorities of AFBP by comparing it with the fast factorization backprojection (FFBP) algorithm.},
    doi = {10.1109/LGRS.2013.2295326},
    file = {:zhangLiQiaoXuTGRS2014FastBackProjection.pdf:PDF},
    keywords = {SAR Processing, Fast-Factorized Back-Projection, FFBP,Fast Backprojection, fast Fourier transforms;image fusion;image resolution;interpolation;radar imaging;synthetic aperture radar;transient response;AFBP algorithm;FFBP algorithm;SA fusion;UPC system;WN spectrum domain;accelerated fast backprojection algorithm;fast Fourier transform;fast factorization backprojection algorithm;high-resolution spotlight SAR imaging;image-domain interpolation;impulse response function;interpolation-based fusion;subaperture fusion;synthetic aperture radar;unified polar coordinate system;wavenumber spectrum fusion;Apertures;Azimuth;Image resolution;Imaging;Interpolation;Signal processing algorithms;Synthetic aperture radar;Accelerated fast BP (AFBP);fast backprojection (FBP);fast factorized backprojection (FFBP)},
    pdf = {../../../docs/zhangLiQiaoXuTGRS2014FastBackProjection.pdf},
    
    }
    


  36. Xiao Xiang Zhu and Richard Bamler. Superresolving SAR Tomography for Multidimensional Imaging of Urban Areas: Compressive sensing-based TomoSAR inversion. IEEE Signal Processing Magazine, 31(4):51-58, July 2014. Keyword(s): SAR Processing, SAR Tomography, PSI, Persistent Scatterer Interferometry, Deformation Monitoring, Deformation, compressed sensing, image motion analysis, image reconstruction, radar imaging, radar resolution, synthetic aperture radar, tomography, 4D point clouds, LiDAR, VHR spaceborne tomographic SAR inversion, building deformation, compressive sensing-based TomoSAR inversion, dynamic city model reconstruction, motion reconstruction, multicomponent nonlinear motion, multidimensional imaging, multiple scatterers, point density, shape reconstruction, synthetic aperture radar, urban areas, urban infrastructure, very high spatial resolution SAR tomography, Mathematical model, Signal processing algorithms, Signal resolution, Signal to noise ratio, Synthetic aperture radar, Tomography, Urban areas.
    Abstract: With reference to the current status of VHR spaceborne tomographic SAR inversion presented in this article, the following conclusions can be drawn: VHR tomographic SAR inversion is able to reconstruct the shape and motion of individual buildings and entire city areas. SR is crucial and possible, e.g., using CS, for VHR tomographic SAR inversion for urban infrastructure. The motion or deformation of buildings is often nonlinear (periodic, accelerating, stepwise, etc.). Multicomponent nonlinear motion of multiple scatterers can be separated. The 4-D point clouds retrieved by VHR TomoSAR has a point density comparable to LiDAR and can be potentially used for dynamic city model reconstruction.

    @Article{zhuBamlerIEEESigProcMag2014TOMOSAR,
    author = {Xiao Xiang Zhu and Bamler, Richard},
    title = {Superresolving {SAR} Tomography for Multidimensional Imaging of Urban Areas: Compressive sensing-based {TomoSAR} inversion},
    journal = {IEEE Signal Processing Magazine},
    year = {2014},
    volume = {31},
    number = {4},
    pages = {51-58},
    month = jul,
    issn = {1053-5888},
    abstract = {With reference to the current status of VHR spaceborne tomographic SAR inversion presented in this article, the following conclusions can be drawn: VHR tomographic SAR inversion is able to reconstruct the shape and motion of individual buildings and entire city areas. SR is crucial and possible, e.g., using CS, for VHR tomographic SAR inversion for urban infrastructure. The motion or deformation of buildings is often nonlinear (periodic, accelerating, stepwise, etc.). Multicomponent nonlinear motion of multiple scatterers can be separated. The 4-D point clouds retrieved by VHR TomoSAR has a point density comparable to LiDAR and can be potentially used for dynamic city model reconstruction.},
    doi = {10.1109/MSP.2014.2312098},
    file = {:zhuBamlerIEEESigProcMag2014TOMOSAR.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, PSI, Persistent Scatterer Interferometry, Deformation Monitoring, Deformation, compressed sensing;image motion analysis;image reconstruction;radar imaging;radar resolution;synthetic aperture radar;tomography;4D point clouds;LiDAR;VHR spaceborne tomographic SAR inversion;building deformation;compressive sensing-based TomoSAR inversion;dynamic city model reconstruction;motion reconstruction;multicomponent nonlinear motion;multidimensional imaging;multiple scatterers;point density;shape reconstruction;synthetic aperture radar;urban areas;urban infrastructure;very high spatial resolution SAR tomography;Mathematical model;Signal processing algorithms;Signal resolution;Signal to noise ratio;Synthetic aperture radar;Tomography;Urban areas},
    owner = {ofrey},
    pdf = {../../../docs/zhuBamlerIEEESigProcMag2014TOMOSAR.pdf},
    
    }
    


  37. S. Zwieback and I. Hajnsek. Statistical Tests for Symmetries in Polarimetric Scattering Coherency Matrices. IEEE_J_GRSL, 11(1):308-312, January 2014. Keyword(s): airborne radar, covariance matrices, geophysical equipment, geophysical techniques, invariance, radar polarimetry, scattering, statistical testing, Freeman-Durden decomposition, SAR polarimetry, airborne L-band data, covariance matrix, likelihood-ratio testing, mature rape field, polarimetric scattering coherency matrix, reflection invariance hypothesis, reflection symmetry, second-order statistics, statistical testing, synthetic aperture radar polarimetry, vegetation growth, Parametric statistics, polarimetric synthetic aperture radar, radar remote sensing.
    @Article{Zwieback2014b,
    author = {S. Zwieback and I. Hajnsek},
    title = {Statistical Tests for Symmetries in Polarimetric Scattering Coherency Matrices},
    year = {2014},
    volume = {11},
    number = {1},
    month = jan,
    pages = {308--312},
    issn = {1545-598X},
    doi = {10.1109/LGRS.2013.2257160},
    journal = IEEE_J_GRSL,
    keywords = {airborne radar, covariance matrices, geophysical equipment, geophysical techniques, invariance, radar polarimetry, scattering, statistical testing, Freeman-Durden decomposition, SAR polarimetry, airborne L-band data, covariance matrix, likelihood-ratio testing, mature rape field, polarimetric scattering coherency matrix, reflection invariance hypothesis, reflection symmetry, second-order statistics, statistical testing, synthetic aperture radar polarimetry, vegetation growth, Parametric statistics, polarimetric synthetic aperture radar, radar remote sensing},
    owner = {ofrey},
    
    }
    


  38. M. \cCetin, I. Stojanovic, N.O. Önhon, K.R. Varshney, S. Samadi, W.C. Karl, and A.S. Willsky. Sparsity-Driven Synthetic Aperture Radar Imaging: Reconstruction, autofocusing, moving targets, and compressed sensing. etationationToImprovePrecipitati, 31(4):27-40, July 2014. Keyword(s): SAR Processing, Autofocus, compressed sensing, image representation, radar imaging, synthetic aperture radar, SAR image formation, SAR sensing mission design, anisotropy characterization, compressed sensing-based analysis, joint autofocusing, joint imaging, phase errors, sparsity-based methods, sparsity-driven synthetic aperture radar imaging, synthesis-based sparse signal representation formulations, wide-angle SAR imaging, Image reconstruction, Imaging, Radar imaging, Radar polarimetry, Scattering, Synthetic aperture radar.
    Abstract: This article presents a survey of recent research on sparsity-driven synthetic aperture radar (SAR) imaging. In particular, it reviews 1) the analysis and synthesis-based sparse signal representation formulations for SAR image formation together with the associated imaging results, 2) sparsity-based methods for wide-angle SAR imaging and anisotropy characterization, 3) sparsity-based methods for joint imaging and autofocusing from data with phase errors, 4) techniques for exploiting sparsity for SAR imaging of scenes containing moving objects, and 5) recent work on compressed sensing (CS)-based analysis and design of SAR sensing missions.

    @Article{cetinStojanovicOnhonVarshneySamadiKarlWillskyIEEESigProcMag2014CompressiveSensingSAR,
    author = {\c{C}etin, M. and Stojanovi\'{c}, I. and \"Onhon, N.O. and Varshney, K.R. and Samadi, S. and Karl, W.C. and Willsky, A.S.},
    title = {Sparsity-Driven Synthetic Aperture Radar Imaging: Reconstruction, autofocusing, moving targets, and compressed sensing},
    journal = {IEEE Signal Processing Magazine},
    year = {2014},
    volume = {31},
    number = {4},
    pages = {27-40},
    month = jul,
    issn = {1053-5888},
    abstract = {This article presents a survey of recent research on sparsity-driven synthetic aperture radar (SAR) imaging. In particular, it reviews 1) the analysis and synthesis-based sparse signal representation formulations for SAR image formation together with the associated imaging results, 2) sparsity-based methods for wide-angle SAR imaging and anisotropy characterization, 3) sparsity-based methods for joint imaging and autofocusing from data with phase errors, 4) techniques for exploiting sparsity for SAR imaging of scenes containing moving objects, and 5) recent work on compressed sensing (CS)-based analysis and design of SAR sensing missions.},
    doi = {10.1109/MSP.2014.2312834},
    file = {:cetinStojanovicOnhonVarshneySamadiKarlWillskyIEEESigProcMag2014CompressiveSensingSAR.pdf:PDF},
    keywords = {SAR Processing, Autofocus, compressed sensing;image representation;radar imaging;synthetic aperture radar;SAR image formation;SAR sensing mission design;anisotropy characterization;compressed sensing-based analysis;joint autofocusing;joint imaging;phase errors;sparsity-based methods;sparsity-driven synthetic aperture radar imaging;synthesis-based sparse signal representation formulations;wide-angle SAR imaging;Image reconstruction;Imaging;Radar imaging;Radar polarimetry;Scattering;Synthetic aperture radar},
    owner = {ofrey},
    pdf = {../../../docs/cetinStojanovicOnhonVarshneySamadiKarlWillskyIEEESigProcMag2014CompressiveSensingSAR.pdf},
    
    }
    


Conference articles

  1. Alex Coccia, Stefano Tebaldini, and Adriano Meta. Preliminary results from most recent SAR airborne campaigns by MetaSensing. In Proc. SPIE, volume 9245, pages 92450L-92450L-7, 2014.
    Abstract: MetaSensing B.V.1 is a Dutch company producing and operating Synthetic Aperture Radar (SAR) sensors at high resolution and different frequency bands, including P-, L-, C-, X- and Ku. By operating its most recent SAR sensors in the framework of different projects MetaSensing showed how diverse SAR imagery techniques can be applied to different areas of remote sensing, offering an effective tool for monitoring and mapping purposes. The present paper gives an overview about the last achievements of MetaSensing during a recent airborne measurement mission within the AlpTomoExpcampaign, also showing some preliminary results. A fully-polarimetric L-band radar system has been successfully operated in March 2014 within the framework of the future SAOCOM+ mission currently under investigation by the European Space Agency (ESA). At these low frequencies penetration capabilities for several meters is possible on dry snow. More than 40 fully polarimetric images have been focused by MetaSensing of a glacier of the Otzal Alps, in Austria, within the framework of the AlpTomoExp campaign. Thanks to the good interferometric coherence of the acquired images, further tomographic processing has been possible for 3D images generation showing the vertical profile of the monitored scenario.

    @InProceedings{cocciaTebaldiniMetaSPIE2014AirborneSARTomoSAR,
    author = {Coccia, Alex and Tebaldini, Stefano and Meta, Adriano},
    booktitle = {Proc. SPIE},
    title = {Preliminary results from most recent {SAR} airborne campaigns by {MetaSensing}},
    year = {2014},
    pages = {92450L-92450L-7},
    volume = {9245},
    abstract = {MetaSensing B.V.1 is a Dutch company producing and operating Synthetic Aperture Radar (SAR) sensors at high resolution and different frequency bands, including P-, L-, C-, X- and Ku. By operating its most recent SAR sensors in the framework of different projects MetaSensing showed how diverse SAR imagery techniques can be applied to different areas of remote sensing, offering an effective tool for monitoring and mapping purposes. The present paper gives an overview about the last achievements of MetaSensing during a recent airborne measurement mission within the AlpTomoExpcampaign, also showing some preliminary results. A fully-polarimetric L-band radar system has been successfully operated in March 2014 within the framework of the future SAOCOM+ mission currently under investigation by the European Space Agency (ESA). At these low frequencies penetration capabilities for several meters is possible on dry snow. More than 40 fully polarimetric images have been focused by MetaSensing of a glacier of the Otzal Alps, in Austria, within the framework of the AlpTomoExp campaign. Thanks to the good interferometric coherence of the acquired images, further tomographic processing has been possible for 3D images generation showing the vertical profile of the monitored scenario.},
    doi = {10.1117/12.2067331},
    file = {:cocciaTebaldiniMetaSPIE2014AirborneSARTomoSAR.pdf:PDF},
    pdf = {../../../docs/cocciaTebaldiniMetaSPIE2014AirborneSARTomoSAR.pdf},
    url = {http://dx.doi.org/10.1117/12.2067331},
    
    }
    


  2. T. J. Czernuszewicz, J. W. Homeister, M. C. Caughey, M. A. Farber, J. J. Fulton, P. F. Ford, W. A. Marston, R. Vallabhaneni, T. C. Nichols, and C. M. Gallippi. In vivo characterization of atherosclerotic plaque of human carotid arteries with histopathological correlation using ARFI ultrasound. In Proc. IEEE Int. Ultrasonics Symp, pages 1794-1797, September 2014. Keyword(s): bioacoustics, biological tissues, biomedical ultrasonics, blood vessels, haemodynamics, phantoms, ultrasonic imaging, ARFI ultrasound, acoustic radiation force impulse imaging, atherosclerotic pigs, calcification, carotid atherosclerotic plaques, clinically-indicated carotid endarterectomy, dense fibrosis, histopathological correlation, human carotid arteries, inflammation, mechanical properties, mild intraplaque hemorrhage, necrotic cores, phantoms, plaque rupture, spatially-matched histopathology, stiff tissue, ultrasound imaging plane, Acoustics, Atherosclerosis, Carotid arteries, Force, Imaging, In vivo, Ultrasonic imaging, ARFI, CEA, acoustic radiation force, atherosclerosis, carotid endarterectomy, plaque characterization, stroke.
    @InProceedings{Czernuszewicz2014,
    author = {T. J. Czernuszewicz and J. W. Homeister and M. C. Caughey and M. A. Farber and J. J. Fulton and P. F. Ford and W. A. Marston and R. Vallabhaneni and T. C. Nichols and C. M. Gallippi},
    title = {In vivo characterization of atherosclerotic plaque of human carotid arteries with histopathological correlation using ARFI ultrasound},
    booktitle = {Proc. IEEE Int. Ultrasonics Symp},
    year = {2014},
    month = sep,
    pages = {1794--1797},
    doi = {10.1109/ULTSYM.2014.0445},
    issn = {1051-0117},
    keywords = {bioacoustics, biological tissues, biomedical ultrasonics, blood vessels, haemodynamics, phantoms, ultrasonic imaging, ARFI ultrasound, acoustic radiation force impulse imaging, atherosclerotic pigs, calcification, carotid atherosclerotic plaques, clinically-indicated carotid endarterectomy, dense fibrosis, histopathological correlation, human carotid arteries, inflammation, mechanical properties, mild intraplaque hemorrhage, necrotic cores, phantoms, plaque rupture, spatially-matched histopathology, stiff tissue, ultrasound imaging plane, Acoustics, Atherosclerosis, Carotid arteries, Force, Imaging, In vivo, Ultrasonic imaging, ARFI, CEA, acoustic radiation force, atherosclerosis, carotid endarterectomy, plaque characterization, stroke},
    owner = {ofrey},
    
    }
    


  3. Laurent Ferro-Famil, Stefano Tebaldini, Matthieu Davy, and Frederic Boute. 3D SAR imaging of the snowpack at X- and Ku-Band: results from the AlpSAR campaign. In Proc. of EUSAR 2014 - 10th European Conference on Synthetic Aperture Radar, pages 1-4, June 2014. Keyword(s): SAR Processing, SAR Tomography, Snow, Snowpack, X-band, Ku-band.
    Abstract: In this paper we present results obtained by processing the ground based SAR (GBSAR) data collected in february 2013 on the Austrian Alps in the frame of the ESA campaign AlpSAR. The GBSAR was operated at X- and Ku-Band with a bandwidth of 4 GHz and employing a 2D synthetic aperture, resulting in 3D resolution capabilities at a resolution of few centimeters. Images produced at two different sites reveal the presence of multiple layers within the snowpack. The strongest backscatter contributions have been observed to correspond to bottom layers, that dominate the ones from the snow/air interface and the near subsurface. GBSAR data are observed to provide sensitivity to the propagation velocity into the snowpack, as revealed by the apparent depth variation with respect to the incidence angle.

    @InProceedings{ferroFamilTebaldiniDavyBouteEUSAR2014SnowTomo,
    Title = {{3D} {SAR} imaging of the snowpack at {X}- and {Ku}-Band: results from the {AlpSAR} campaign},
    Author = {Laurent Ferro-Famil and Stefano Tebaldini and Matthieu Davy and Frederic Boute},
    Booktitle = {Proc. of EUSAR 2014 - 10th European Conference on Synthetic Aperture Radar},
    Month = jun,
    Pages = {1-4},
    Year = {2014},
    Abstract = {In this paper we present results obtained by processing the ground based SAR (GBSAR) data collected in february 2013 on the Austrian Alps in the frame of the ESA campaign AlpSAR. The GBSAR was operated at X- and Ku-Band with a bandwidth of 4 GHz and employing a 2D synthetic aperture, resulting in 3D resolution capabilities at a resolution of few centimeters. Images produced at two different sites reveal the presence of multiple layers within the snowpack. The strongest backscatter contributions have been observed to correspond to bottom layers, that dominate the ones from the snow/air interface and the near subsurface. GBSAR data are observed to provide sensitivity to the propagation velocity into the snowpack, as revealed by the apparent depth variation with respect to the incidence angle.},
    Keywords = {SAR Processing, SAR Tomography, Snow, Snowpack, X-band, Ku-band},
    Pdf = {../../../docs/ferroFamilTebaldiniDavyBouteEUSAR2014SnowTomo.pdf} 
    }
    


  4. Laurent Ferro-Famil, Stefano Tebaldini, Matthieu Davy, and Frederic Boute. 3D SAR imaging of the snowpack in presence of propagation velocity changes: Results from the AlpSAR campaign. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 3370-3373, July 2014. Keyword(s): SAR Processing, SAR Tomography, Snow, Snowpack, X-band, Ku-band, geophysical image processing, image resolution, radar imaging, snow, synthetic aperture radar, terrain mapping, 2D synthetic aperture, 3D SAR imaging, 3D resolution capabilities, AD 2013 02, AlpSAR campaign, ESA campaign, GBSAR data, Ku-Band, X-band, apparent depth variation, backscatter contributions, propagation velocity, propagation velocity change, snow-air interface, snowpack, Communication channels, Equations, Scattering, Sensitivity, Snow, Synthetic aperture radar, Three-dimensional displays.
    Abstract: In this paper we present results relative to the 3D GBSAR surveys acquired in february 2013 on the Austrian Alps as a part of the ESA campaign AlpSAR. The GBSAR was operated at X- and Ku-Band with a bandwidth of 4 GHz and employing a 2D synthetic aperture, resulting in 3D resolution capabilities at a resolution of few centimeters. Images produced at two different sites reveal the presence of multiple layers within the snowpack. The strongest backscatter contributions have been observed to correspond to bottom layers, that dominate the ones from the snow/air interface and the near subsurface. GBSAR data are observed to provide sensitivity to the propagation velocity into the snowpack, as revealed by the apparent depth variation with respect to the incidence angle.

    @InProceedings{ferroFamilTebaldiniDavyBouteIGARSS2014SnowTomo,
    author = {Laurent Ferro-Famil and Stefano Tebaldini and Matthieu Davy and Frederic Boute},
    title = {{3D} {SAR} imaging of the snowpack in presence of propagation velocity changes: Results from the {AlpSAR} campaign},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2014},
    pages = {3370-3373},
    month = jul,
    abstract = {In this paper we present results relative to the 3D GBSAR surveys acquired in february 2013 on the Austrian Alps as a part of the ESA campaign AlpSAR. The GBSAR was operated at X- and Ku-Band with a bandwidth of 4 GHz and employing a 2D synthetic aperture, resulting in 3D resolution capabilities at a resolution of few centimeters. Images produced at two different sites reveal the presence of multiple layers within the snowpack. The strongest backscatter contributions have been observed to correspond to bottom layers, that dominate the ones from the snow/air interface and the near subsurface. GBSAR data are observed to provide sensitivity to the propagation velocity into the snowpack, as revealed by the apparent depth variation with respect to the incidence angle.},
    doi = {10.1109/IGARSS.2014.6947203},
    file = {:ferroFamilTebaldiniDavyBouteIGARSS2014SnowTomo.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Snow, Snowpack, X-band, Ku-band, geophysical image processing;image resolution;radar imaging;snow;synthetic aperture radar;terrain mapping;2D synthetic aperture;3D SAR imaging;3D resolution capabilities;AD 2013 02;AlpSAR campaign;ESA campaign;GBSAR data;Ku-Band;X-band;apparent depth variation;backscatter contributions;propagation velocity;propagation velocity change;snow-air interface;snowpack;Communication channels;Equations;Scattering;Sensitivity;Snow;Synthetic aperture radar;Three-dimensional displays},
    pdf = {../../../docs/ferroFamilTebaldiniDavyBouteIGARSS2014SnowTomo.pdf},
    
    }
    


  5. Othmar Frey, Irena Hajnsek, Urs Wegmuller, and Charles L. Werner. SAR tomography based 3-D point cloud extraction of point-like scatterers in urban areas. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 1313-1316, July 2014. Keyword(s): SAR Processing, SAR tomography, Synthetic aperture radar (SAR), SAR Interferometry, InSAR, interferometric stacking, persistent scatterer interferometry, PSI, spaceborne SAR radar interferometry, spaceborne radar, X-Band, TerraSAR-X, synthetic aperture radar, tomography, 3-D point cloud retrieval, Barcelona, SAR tomography based 3-D point cloud extraction, high-resolution spaceborne TerraSAR-X data, interferometric stack, high-rise building vertical tomographic slice, layover scenario case, persistent scatterer interferometry, PSI, point-like scatterer, processing approach, Urban Remote Sensing, Spaceborne radar, Synthetic aperture radar, Three-dimensional displays, Tomography, 3-D point cloud, SAR interferometry.
    Abstract: SAR tomography as an extension to persistent scatterer interferometry (PSI) approaches has the potential to improve the level of detail of retrievable information, in particular, in the case of layover scenarios in urban areas. In this paper, a processing approach is sketched that eventually allows for retrieving a 3-D point cloud of point-like scatterers based on subsequent PSI and SAR tomography processing of an interferometric stack of high-resolution spaceborne TerraSAR-X data acquired over the city of Barcelona between the years 2008 and 2012. Experimental results are presented in the form of (1) vertical tomographic slices of high-rise buildings and (2) a 3-D point cloud of a larger district of the city of Barcelona retrieved from the tomograms.

    @InProceedings{freyHajnsekWegmullerWernerIGARSS2014TomoTSXBarca,
    author = {Frey, Othmar and Hajnsek, Irena and Wegmuller, Urs and Werner, Charles L.},
    title = {{SAR} tomography based {3-D} point cloud extraction of point-like scatterers in urban areas},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2014},
    pages = {1313-1316},
    month = jul,
    abstract = {SAR tomography as an extension to persistent scatterer interferometry (PSI) approaches has the potential to improve the level of detail of retrievable information, in particular, in the case of layover scenarios in urban areas. In this paper, a processing approach is sketched that eventually allows for retrieving a 3-D point cloud of point-like scatterers based on subsequent PSI and SAR tomography processing of an interferometric stack of high-resolution spaceborne TerraSAR-X data acquired over the city of Barcelona between the years 2008 and 2012. Experimental results are presented in the form of (1) vertical tomographic slices of high-rise buildings and (2) a 3-D point cloud of a larger district of the city of Barcelona retrieved from the tomograms.},
    doi = {10.1109/IGARSS.2014.6946675},
    file = {:freyHajnsekWegmullerWernerIGARSS2014TomoTSXBarca.pdf:PDF},
    keywords = {SAR Processing, SAR tomography; Synthetic aperture radar (SAR); SAR Interferometry, InSAR, interferometric stacking;persistent scatterer interferometry; PSI, spaceborne SAR radar interferometry;spaceborne radar; X-Band, TerraSAR-X, synthetic aperture radar;tomography;3-D point cloud retrieval; Barcelona; SAR tomography based 3-D point cloud extraction; high-resolution spaceborne TerraSAR-X data, interferometric stack;high-rise building vertical tomographic slice; layover scenario case;persistent scatterer interferometry; PSI, point-like scatterer;processing approach;Urban Remote Sensing; Spaceborne radar;Synthetic aperture radar;Three-dimensional displays;Tomography; 3-D point cloud;SAR interferometry},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyHajnsekWegmullerWernerIGARSS2014TomoTSXBarca.pdf},
    
    }
    


  6. Othmar Frey, Muhammad Adnan Siddique, Irena Hajnsek, Urs Wegmuller, and Charles L. Werner. Combining SAR tomography and a PSI approach for highresolution 3-D imaging of an urban area. In Proc. of EUSAR 2014 - 10th European Conference on Synthetic Aperture Radar, pages 1-4, June 2014. Keyword(s): SAR Processing, SAR tomography, Synthetic aperture radar (SAR), SAR Interferometry, InSAR, interferometric stacking, persistent scatterer interferometry, PSI, spaceborne SAR radar interferometry, spaceborne radar, X-Band, TerraSAR-X, synthetic aperture radar, tomography, 3-D point cloud retrieval, Barcelona, SAR tomography based 3-D point cloud extraction, high-resolution spaceborne TerraSAR-X data, interferometric stack, high-rise building vertical tomographic slice, layover scenario case, persistent scatterer interferometry, PSI, point-like scatterer, processing approach, Urban Remote Sensing, Spaceborne radar, Synthetic aperture radar, Three-dimensional displays, Tomography, 3-D point cloud, SAR interferometry.
    Abstract: Combining persistent scatterer interferometry (PSI) and SAR tomography approaches has the potential to overcome layover scenarios in urban areas and may thus increase the level of detail of differential interferometric measurements of displacements in such environments. In this paper, we report the current status and results of our efforts to integrate SAR tomography into an operational interferometric point target analysis (IPTA) processing tool as an extension to the conventional persistent scatterer interferometry approach. In particular, the PSI and the SAR tomography processing approaches applied are highlighted. In addition, details in the form of tomographic slices of two high-rise buildings are presented as well as a 3-D point cloud reconstruction of parts of the city of Barcelona are shown, as extracted from an interferometric stack of high-resolution stripmap-mode SAR data at X-band acquired by the TerraSAR-X spaceborne SAR sensor.

    @InProceedings{freySiddiqueHajnsekWegmullerWernerEUSAR2014TomoTSXBarca,
    author = {Frey, Othmar and Siddique, Muhammad Adnan and Hajnsek, Irena and Wegmuller, Urs and Werner, Charles L.},
    title = {Combining {SAR} tomography and a {PSI} approach for highresolution {3-D} imaging of an urban area},
    booktitle = {Proc. of EUSAR 2014 - 10th European Conference on Synthetic Aperture Radar},
    year = {2014},
    pages = {1-4},
    month = jun,
    abstract = {Combining persistent scatterer interferometry (PSI) and SAR tomography approaches has the potential to overcome layover scenarios in urban areas and may thus increase the level of detail of differential interferometric measurements of displacements in such environments. In this paper, we report the current status and results of our efforts to integrate SAR tomography into an operational interferometric point target analysis (IPTA) processing tool as an extension to the conventional persistent scatterer interferometry approach. In particular, the PSI and the SAR tomography processing approaches applied are highlighted. In addition, details in the form of tomographic slices of two high-rise buildings are presented as well as a 3-D point cloud reconstruction of parts of the city of Barcelona are shown, as extracted from an interferometric stack of high-resolution stripmap-mode SAR data at X-band acquired by the TerraSAR-X spaceborne SAR sensor.},
    file = {:freySiddiqueHajnsekWegmullerWernerEUSAR2014TomoTSXBarca.pdf:PDF},
    keywords = {SAR Processing, SAR tomography; Synthetic aperture radar (SAR); SAR Interferometry, InSAR, interferometric stacking;persistent scatterer interferometry; PSI, spaceborne SAR radar interferometry;spaceborne radar; X-Band, TerraSAR-X, synthetic aperture radar;tomography;3-D point cloud retrieval; Barcelona; SAR tomography based 3-D point cloud extraction; high-resolution spaceborne TerraSAR-X data, interferometric stack;high-rise building vertical tomographic slice; layover scenario case;persistent scatterer interferometry; PSI, point-like scatterer;processing approach;Urban Remote Sensing; Spaceborne radar;Synthetic aperture radar;Three-dimensional displays;Tomography; 3-D point cloud;SAR interferometry},
    owner = {ofrey},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freySiddiqueHajnsekWegmullerWernerEUSAR2014TomoTSXBarca.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6856979},
    
    }
    


  7. Othmar Frey, Charles L. Werner, and Urs Wegmuller. GPU-based parallelized time-domain back-projection processing for agile SAR platforms. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 1132-1135, July 2014. Keyword(s): SAR Processing, Azimuth Focusing, Time-Domain Back-Projection, TDBP, SAR focusing, GPU, GPU-based parallelized TDBP, graphics processing units, motion compensation, parallel processing, radar signal processing, synthetic aperture radar, 3D motion compensation, GPU based backprojection processing, NVIDIA CUDA GPU computing framework, SAR processing scheme, agile SAR platforms, car borne SAR data set, nonlinear sensor trajectories, parallelized backprojection processing, single look complex SAR images, slant azimuth geometry, slant range geometry, synthetic aperture, time domain backprojection processing, Azimuth, Focusing, Graphics processing units, Remote sensing, Synthetic aperture radar, Time-domain analysis, Azimuth focusing, CARSAR, CUDA, GPU, Nonlinear Sensor Trajectory, Parallelization, SAR imaging, SAR interferometry, Synthetic aperture radar (SAR), car-borne SAR, ground-based SAR system.
    Abstract: Agile SAR platforms such as an automobile require a flexible SAR processing scheme to account for nonlinear sensor trajectories during the synthetic aperture. In this contribution, a parallelized implementation of a time-domain back-projection SAR focusing algorithm based on NVIDIA's CUDA GPU computing framework is presented and discussed using a car-borne SAR data set. The processing performance is assessed using different hardware. In addition, a pre-processing scheme is described that allows for full 3-D motion compensation, yet staying conveniently in conventional slant-range/azimuth geometry of single-look complex SAR images.

    @InProceedings{freyWernerWegmullerIGARSS2014GPUbasedTDBP,
    author = {Frey, Othmar and Werner, Charles L. and Wegmuller, Urs},
    title = {{GPU}-based parallelized time-domain back-projection processing for agile {SAR} platforms},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2014},
    pages = {1132-1135},
    month = jul,
    abstract = {Agile SAR platforms such as an automobile require a flexible SAR processing scheme to account for nonlinear sensor trajectories during the synthetic aperture. In this contribution, a parallelized implementation of a time-domain back-projection SAR focusing algorithm based on NVIDIA's CUDA GPU computing framework is presented and discussed using a car-borne SAR data set. The processing performance is assessed using different hardware. In addition, a pre-processing scheme is described that allows for full 3-D motion compensation, yet staying conveniently in conventional slant-range/azimuth geometry of single-look complex SAR images.},
    doi = {10.1109/IGARSS.2014.6946629},
    file = {:freyWernerWegmullerIGARSS2014GPUbasedTDBP.pdf:PDF},
    keywords = {SAR Processing, Azimuth Focusing, Time-Domain Back-Projection, TDBP, SAR focusing, GPU, GPU-based parallelized TDBP, graphics processing units;motion compensation;parallel processing;radar signal processing;synthetic aperture radar; 3D motion compensation;GPU based backprojection processing;NVIDIA CUDA GPU computing framework; SAR processing scheme;agile SAR platforms;car borne SAR data set;nonlinear sensor trajectories; parallelized backprojection processing;single look complex SAR images;slant azimuth geometry;slant range geometry;synthetic aperture; time domain backprojection processing;Azimuth;Focusing;Graphics processing units; Remote sensing;Synthetic aperture radar;Time-domain analysis; Azimuth focusing;CARSAR;CUDA;GPU;Nonlinear Sensor Trajectory; Parallelization;SAR imaging;SAR interferometry;Synthetic aperture radar (SAR); car-borne SAR;ground-based SAR system},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyWernerWegmullerIGARSS2014GPUbasedTDBP.pdf},
    
    }
    


  8. G. Gomba, M. Eineder, A. Parizzi, and R. Bamler. High-resolution estimation of ionospheric phase screens through semi-focusing processing. In Proc. IEEE Geoscience and Remote Sensing Symp, pages 17-20, July 2014. Keyword(s): SAR Processing, split-spectrum, split-spectrum interferometry, split-band, split-band interferometry, geophysical techniques, ionospheric electromagnetic wave propagation, radar imaging, radar interferometry, remote sensing by radar, synthetic aperture radar, SAR images, blurring, coherence, decorrelation, delta-k split-band interferometry method, high-resolution estimation, ionosphere irregularities, ionospheric azimuth effect, ionospheric phase screens, semifocusing processing, synthetic aperture generate shift, turbulent ionosphere, Apertures, Azimuth, Coherence, Estimation, Focusing, Ionosphere, Synthetic aperture radar, InSAR, SAR ionospheric effects, ionosphere estimation, ionosphere scintillation.
    Abstract: Ionosphere irregularities along the synthetic aperture generate shifts and blurring that cause decorrelation. In this paper it is shown how, by partially focusing SAR images to the height of the ionosphere, it is possible to reduce the ionospheric azimuth effects and increase the coherence. This permits, even in case of turbulent ionosphere, to obtain better accuracies when separating the deformations phase from the ionospheric phase using the delta-k split-band interferometry method.

    @InProceedings{gombaEinederParizziBamler2014IonoPhaseEstimation,
    author = {G. Gomba and M. Eineder and A. Parizzi and R. Bamler},
    title = {High-resolution estimation of ionospheric phase screens through semi-focusing processing},
    booktitle = {Proc. IEEE Geoscience and Remote Sensing Symp},
    year = {2014},
    pages = {17--20},
    month = jul,
    abstract = {Ionosphere irregularities along the synthetic aperture generate shifts and blurring that cause decorrelation. In this paper it is shown how, by partially focusing SAR images to the height of the ionosphere, it is possible to reduce the ionospheric azimuth effects and increase the coherence. This permits, even in case of turbulent ionosphere, to obtain better accuracies when separating the deformations phase from the ionospheric phase using the delta-k split-band interferometry method.},
    doi = {10.1109/IGARSS.2014.6946344},
    issn = {2153-6996},
    keywords = {SAR Processing, split-spectrum, split-spectrum interferometry, split-band, split-band interferometry,geophysical techniques, ionospheric electromagnetic wave propagation, radar imaging, radar interferometry, remote sensing by radar, synthetic aperture radar, SAR images, blurring, coherence, decorrelation, delta-k split-band interferometry method, high-resolution estimation, ionosphere irregularities, ionospheric azimuth effect, ionospheric phase screens, semifocusing processing, synthetic aperture generate shift, turbulent ionosphere, Apertures, Azimuth, Coherence, Estimation, Focusing, Ionosphere, Synthetic aperture radar, InSAR, SAR ionospheric effects, ionosphere estimation, ionosphere scintillation},
    owner = {ofrey},
    
    }
    


  9. O. Ponce, P. Prats, R. Scheiber, A. Reigber, and A. Moreira. Study of the 3-D Impulse Response Function of Holographic SAR Tomography with Multicircular Acquisitions. In Proc. EUSAR 2014; 10th European Conf. Synthetic Aperture Radar, pages 1-4, June 2014.
    @InProceedings{Ponce2014a,
    author = {O. Ponce and P. Prats and R. Scheiber and A. Reigber and A. Moreira},
    title = {Study of the {3-D} Impulse Response Function of Holographic {SAR} Tomography with Multicircular Acquisitions},
    booktitle = {Proc. EUSAR 2014; 10th European Conf. Synthetic Aperture Radar},
    year = {2014},
    month = jun,
    pages = {1--4},
    owner = {ofrey},
    
    }
    


  10. O. Ponce, T. Rommel, M. Younis, P. Prats, and A. Moreira. Multiple-input multiple-output circular SAR. In Proc. 15th Int. Radar Symp. (IRS), pages 1-5, June 2014. Keyword(s): MIMO radar, radar imaging, synthetic aperture radar, 3-D reconstruction, CSAR, HPBW, MCRA, MIMO techniques, PRF, SCORE, circular synthetic aperture radar, holoSAR imaging, minimum half-power beamwidth, multichannel reconstruction in azimuth, multicircular SAR acquisitions, multiple-input multiple-output circular SAR, orthogonal waveforms, pulse repetition frequency, quadpolarized systems, range ambiguity, range-azimuth directions, scan-on-receive, spotlighted region, subwavelength resolution, Apertures, Azimuth, Imaging, MIMO, Radar imaging, Synthetic aperture radar, Circular SAR, digital beam forming (DBF), multicircular SAR, multiple-input multiple-output (MIMO), synthetic aperture radar (SAR).
    @InProceedings{Ponce2014,
    author = {O. Ponce and T. Rommel and M. Younis and P. Prats and A. Moreira},
    title = {Multiple-input multiple-output circular {SAR}},
    booktitle = {Proc. 15th Int. Radar Symp. (IRS)},
    year = {2014},
    month = jun,
    pages = {1--5},
    doi = {10.1109/IRS.2014.6869262},
    issn = {2155-5745},
    keywords = {MIMO radar, radar imaging, synthetic aperture radar, 3-D reconstruction, CSAR, HPBW, MCRA, MIMO techniques, PRF, SCORE, circular synthetic aperture radar, holoSAR imaging, minimum half-power beamwidth, multichannel reconstruction in azimuth, multicircular SAR acquisitions, multiple-input multiple-output circular SAR, orthogonal waveforms, pulse repetition frequency, quadpolarized systems, range ambiguity, range-azimuth directions, scan-on-receive, spotlighted region, subwavelength resolution, Apertures, Azimuth, Imaging, MIMO, Radar imaging, Synthetic aperture radar, Circular SAR, digital beam forming (DBF), multicircular SAR, multiple-input multiple-output (MIMO), synthetic aperture radar (SAR)},
    owner = {ofrey},
    
    }
    


  11. Marc Rodriguez-Cassola, Pau Prats-Iraola, Paco López-Dekker, Andreas Reigber, Gerhard Krieger, and Alberto Moreira. Autonomous time and phase calibration of spaceborne bistatic SAR systems. In EUSAR 2014; 10th European Conference on Synthetic Aperture Radar; Proceedings of, pages 1-4, June 2014.
    Abstract: Bistatic and multistatic SAR constellations offer increased performance at the expense of increased operational complexity. Due to geometric or cost constraints, multistatic SAR constellations might be forced to operate in a partially cooperative manner, i.e., without a direct synchronisation link. In demanding scenarios, like high-resolution bistatic SAR imaging or cross-platform SAR interferometry or tomography, the data need undergo a calibration step to compensate the lack of synchronisation between transmitter and receiver master clocks. Autonomous synchronisation, based on the inversion of the phase and positioning errors of the bistatic SAR images caused by the lack of synchronisation, is used to calibrate the time and phase references of the system with the sole help of the received radar data, which drastically reduces the requirements on the hardware of the system.

    @InProceedings{6856780,
    Title = {Autonomous time and phase calibration of spaceborne bistatic SAR systems},
    Author = {Rodriguez-Cassola, Marc and Prats-Iraola, Pau and L\'opez-Dekker, Paco and Reigber, Andreas and Krieger, Gerhard and Moreira, Alberto},
    Booktitle = {EUSAR 2014; 10th European Conference on Synthetic Aperture Radar; Proceedings of},
    Month = {June},
    Pages = {1-4},
    Year = {2014},
    Abstract = {Bistatic and multistatic SAR constellations offer increased performance at the expense of increased operational complexity. Due to geometric or cost constraints, multistatic SAR constellations might be forced to operate in a partially cooperative manner, i.e., without a direct synchronisation link. In demanding scenarios, like high-resolution bistatic SAR imaging or cross-platform SAR interferometry or tomography, the data need undergo a calibration step to compensate the lack of synchronisation between transmitter and receiver master clocks. Autonomous synchronisation, based on the inversion of the phase and positioning errors of the bistatic SAR images caused by the lack of synchronisation, is used to calibrate the time and phase references of the system with the sole help of the received radar data, which drastically reduces the requirements on the hardware of the system.} 
    }
    


  12. Sabine Rödelsperger and Adriano Meta. MetaSensing's FastGBSAR: ground based radar for deformation monitoring. In Proc. SPIE, volume 9243, pages 924318-924318-8, 2014. Keyword(s): SAR Processing, FastGBSAR, GBSAR, InSAR, Ground-based radar, Ground-based SAR, deformation measurement, displacement, subsidence, terrestrial radar interferometry, mass movements, surface deformation, Dike monitoring, Dike failure.
    Abstract: The continuous monitoring of ground deformation and structural movement has become an important task in engineering. MetaSensing introduces a novel sensor system, the Fast Ground Based Synthetic Aperture Radar (FastGBSAR), based on innovative technologies that have already been successfully applied to airborne SAR applications. The FastGBSAR allows the remote sensing of deformations of a slope or infrastructure from up to a distance of 4 km. The FastGBSAR can be setup in two different configurations: in Real Aperture Radar (RAR) mode it is capable of accurately measuring displacements along a linear range profile, ideal for monitoring vibrations of structures like bridges and towers (displacement accuracy up to 0.01 mm). Modal parameters can be determined within half an hour. Alternatively, in Synthetic Aperture Radar (SAR) configuration it produces two-dimensional displacement images with an acquisition time of less than 5 seconds, ideal for monitoring areal structures like dams, landslides and open pit mines (displacement accuracy up to 0.1 mm). The MetaSensing FastGBSAR is the first ground based SAR instrument on the market able to produce two-dimensional deformation maps with this high acquisition rate. By that, deformation time series with a high temporal and spatial resolution can be generated, giving detailed information useful to determine the deformation mechanisms involved and eventually to predict an incoming failure. The system is fully portable and can be quickly installed on bedrock or a basement. The data acquisition and processing can be fully automated leading to a low effort in instrument operation and maintenance. Due to the short acquisition time of FastGBSAR, the coherence between two acquisitions is very high and the phase unwrapping is simplified enormously. This yields a high density of resolution cells with good quality and high reliability of the acquired deformations. The deformation maps can directly be used as input into an Early Warning system, to determine the state and danger of a slope or structure. In this paper, the technical principles of the instrument are described and case studies of different monitoring tasks are presented.

    @InProceedings{roedelspergerMetaSPIE2014FastGBSARDikeDemo,
    author = {R\"odelsperger, Sabine and Meta, Adriano},
    booktitle = {Proc. SPIE},
    title = {MetaSensing's {FastGBSAR}: ground based radar for deformation monitoring},
    year = {2014},
    pages = {924318-924318-8},
    volume = {9243},
    abstract = {The continuous monitoring of ground deformation and structural movement has become an important task in engineering. MetaSensing introduces a novel sensor system, the Fast Ground Based Synthetic Aperture Radar (FastGBSAR), based on innovative technologies that have already been successfully applied to airborne SAR applications. The FastGBSAR allows the remote sensing of deformations of a slope or infrastructure from up to a distance of 4 km. The FastGBSAR can be setup in two different configurations: in Real Aperture Radar (RAR) mode it is capable of accurately measuring displacements along a linear range profile, ideal for monitoring vibrations of structures like bridges and towers (displacement accuracy up to 0.01 mm). Modal parameters can be determined within half an hour. Alternatively, in Synthetic Aperture Radar (SAR) configuration it produces two-dimensional displacement images with an acquisition time of less than 5 seconds, ideal for monitoring areal structures like dams, landslides and open pit mines (displacement accuracy up to 0.1 mm). The MetaSensing FastGBSAR is the first ground based SAR instrument on the market able to produce two-dimensional deformation maps with this high acquisition rate. By that, deformation time series with a high temporal and spatial resolution can be generated, giving detailed information useful to determine the deformation mechanisms involved and eventually to predict an incoming failure. The system is fully portable and can be quickly installed on bedrock or a basement. The data acquisition and processing can be fully automated leading to a low effort in instrument operation and maintenance. Due to the short acquisition time of FastGBSAR, the coherence between two acquisitions is very high and the phase unwrapping is simplified enormously. This yields a high density of resolution cells with good quality and high reliability of the acquired deformations. The deformation maps can directly be used as input into an Early Warning system, to determine the state and danger of a slope or structure. In this paper, the technical principles of the instrument are described and case studies of different monitoring tasks are presented.},
    doi = {10.1117/12.2067243},
    file = {:roedelspergerMetaSPIE2014FastGBSARDikeDemo.pdf:PDF},
    keywords = {SAR Processing, FastGBSAR, GBSAR, InSAR, Ground-based radar, Ground-based SAR, deformation measurement, displacement, subsidence, terrestrial radar interferometry, mass movements, surface deformation, Dike monitoring, Dike failure},
    pdf = {../../../docs/roedelspergerMetaSPIE2014FastGBSARDikeDemo.pdf},
    url = {http://dx.doi.org/10.1117/12.2067243},
    
    }
    


  13. Jan Torgrimsson, Patrik Dammert, Hans Hellsten, and Lars M. H. Ulander. Autofocus and analysis of geometrical errors within the framework of fast factorized back-projection. In Proc. SPIE, volume 9093, pages 909303-909303-16, 2014. Keyword(s): SAR Processing, Fast-Factorized Back-Projection, FFBP, Time-Domain Back-Projection, TDBP, Autofocus, SAR Autofocus, Geometrical Autofocus, Airborne SAR, CARABAS, factorized geometrical autofocus algorithm, fast factorized back-projection chain, gain 3 dB, intensity correlation, object function, peak-to-sidelobe ratio measurement, radar imaging, residual space variant range cell migration, ultrawideband synthetic aperture radar processing, Apertures, Electronics packaging, Geometry, Radar tracking, Synthetic aperture radar, Transforms, Autofocus, back-projection, phase gradient algorithm, PGA, synthetic aperture radar (SAR).
    Abstract: This paper describes a Fast Factorized Back-Projection (FFBP) formulation that includes a fully integrated autofocus algorithm, i.e. the Factorized Geometrical Autofocus (FGA) algorithm. The base-two factorization is executed in a horizontal plane, using a Merging (M) and a Range History Preserving (RHP) transform. Six parameters are adopted for each sub-aperture pair, i.e. to establish the geometry stage-by-stage via triangles in 3-dimensional space. If the parameters are derived from navigation data, the algorithm is used as a conventional processing chain. If the parameters on the other hand are varied from a certain factorization step and forward, the algorithm is used as a joint image formation and autofocus strategy. By regulating the geometry at multiple resolution levels, challenging defocusing effects, e.g. residual space-variant Range Cell Migration (RCM), can be corrected. The new formulation also serves another important purpose, i.e. as a parameter characterization scheme. By using the FGA algorithm and its inverse, relations between two arbitrary geometries can be studied, in consequence, this makes it feasible to analyze how errors in navigation data, and topography, affect image focus. The versatility of the factorization procedure is demonstrated successfully on simulated Synthetic Aperture Radar (SAR) data. This is achieved by introducing different GPS/IMU errors and Focus Target Plane (FTP) deviations prior to processing. The characterization scheme is then employed to evaluate the sensitivity, to determine at what step the autofocus function should be activated, and to decide the number of necessary parameters at each step. Resulting FGA images are also compared to a reference image (processed without errors and autofocus) and to a defocused image (processed without autofocus), i.e. to validate the novel approach further.

    @InProceedings{torgrimssonDammertHellstenUlanderFFBPAutofocusSPIE2014,
    author = {Torgrimsson, Jan and Dammert, Patrik and Hellsten, Hans and Ulander, Lars M. H.},
    booktitle = {Proc. SPIE},
    title = {Autofocus and analysis of geometrical errors within the framework of fast factorized back-projection},
    year = {2014},
    pages = {909303-909303-16},
    volume = {9093},
    abstract = {This paper describes a Fast Factorized Back-Projection (FFBP) formulation that includes a fully integrated autofocus algorithm, i.e. the Factorized Geometrical Autofocus (FGA) algorithm. The base-two factorization is executed in a horizontal plane, using a Merging (M) and a Range History Preserving (RHP) transform. Six parameters are adopted for each sub-aperture pair, i.e. to establish the geometry stage-by-stage via triangles in 3-dimensional space. If the parameters are derived from navigation data, the algorithm is used as a conventional processing chain. If the parameters on the other hand are varied from a certain factorization step and forward, the algorithm is used as a joint image formation and autofocus strategy. By regulating the geometry at multiple resolution levels, challenging defocusing effects, e.g. residual space-variant Range Cell Migration (RCM), can be corrected. The new formulation also serves another important purpose, i.e. as a parameter characterization scheme. By using the FGA algorithm and its inverse, relations between two arbitrary geometries can be studied, in consequence, this makes it feasible to analyze how errors in navigation data, and topography, affect image focus. The versatility of the factorization procedure is demonstrated successfully on simulated Synthetic Aperture Radar (SAR) data. This is achieved by introducing different GPS/IMU errors and Focus Target Plane (FTP) deviations prior to processing. The characterization scheme is then employed to evaluate the sensitivity, to determine at what step the autofocus function should be activated, and to decide the number of necessary parameters at each step. Resulting FGA images are also compared to a reference image (processed without errors and autofocus) and to a defocused image (processed without autofocus), i.e. to validate the novel approach further.},
    doi = {10.1117/12.2050048},
    file = {:torgrimssonDammertHellstenUlanderFFBPAutofocusSPIE2014.pdf:PDF},
    keywords = {SAR Processing, Fast-Factorized Back-Projection, FFBP, Time-Domain Back-Projection, TDBP, Autofocus, SAR Autofocus, Geometrical Autofocus, Airborne SAR, CARABAS, factorized geometrical autofocus algorithm; fast factorized back-projection chain;gain 3 dB;intensity correlation;object function;peak-to-sidelobe ratio measurement; radar imaging;residual space variant range cell migration;ultrawideband synthetic aperture radar processing;Apertures; Electronics packaging;Geometry;Radar tracking;Synthetic aperture radar;Transforms; Autofocus;back-projection;phase gradient algorithm, PGA;synthetic aperture radar (SAR)},
    pdf = {../../../docs/torgrimssonDammertHellstenUlanderFFBPAutofocusSPIE2014.pdf},
    url = {http://dx.doi.org/10.1117/12.2050048},
    
    }
    


  14. Jan Torgrimsson, Patrik Dammert, Hans Hellsten, and Lars M. H. Ulander. Autofocus and analysis of geometrical errors within the framework of fast factorized back-projection. In Edmund Zelnio and Frederick D. Garber, editors, Algorithms for Synthetic Aperture Radar Imagery XXI, volume 9093, pages 10 - 25, 2014. International Society for Optics and Photonics, SPIE. Keyword(s): SAR Processing, Synthetic Aperture Radar, Time-Domain Back-Projection, TDBP, Back-Projection, Autofocus, UWB, VHF, Fast Factorized Back-Projection, FFBP.
    Abstract: This paper describes a Fast Factorized Back-Projection (FFBP) formulation that includes a fully integrated autofocus algorithm, i.e. the Factorized Geometrical Autofocus (FGA) algorithm. The base-two factorization is executed in a horizontal plane, using a Merging (M) and a Range History Preserving (RHP) transform. Six parameters are adopted for each sub-aperture pair, i.e. to establish the geometry stage-by-stage via triangles in 3-dimensional space. If the parameters are derived from navigation data, the algorithm is used as a conventional processing chain. If the parameters on the other hand are varied from a certain factorization step and forward, the algorithm is used as a joint image formation and autofocus strategy. By regulating the geometry at multiple resolution levels, challenging defocusing effects, e.g. residual space-variant Range Cell Migration (RCM), can be corrected. The new formulation also serves another important purpose, i.e. as a parameter characterization scheme. By using the FGA algorithm and its inverse, relations between two arbitrary geometries can be studied, in consequence, this makes it feasible to analyze how errors in navigation data, and topography, affect image focus. The versatility of the factorization procedure is demonstrated successfully on simulated Synthetic Aperture Radar (SAR) data. This is achieved by introducing different GPS/IMU errors and Focus Target Plane (FTP) deviations prior to processing. The characterization scheme is then employed to evaluate the sensitivity, to determine at what step the autofocus function should be activated, and to decide the number of necessary parameters at each step. Resulting FGA images are also compared to a reference image (processed without errors and autofocus) and to a defocused image (processed without autofocus), i.e. to validate the novel approach further.

    @InProceedings{torgrimssonDammertHellstenUlanderSPIE2014AutofocusAnalysisGeometricalErrorsFFBackprojection,
    author = {Jan Torgrimsson and Patrik Dammert and Hans Hellsten and Lars M. H. Ulander},
    booktitle = {Algorithms for Synthetic Aperture Radar Imagery XXI},
    title = {{Autofocus and analysis of geometrical errors within the framework of fast factorized back-projection}},
    year = {2014},
    editor = {Edmund Zelnio and Frederick D. Garber},
    organization = {International Society for Optics and Photonics},
    pages = {10 -- 25},
    publisher = {SPIE},
    volume = {9093},
    abstract = {This paper describes a Fast Factorized Back-Projection (FFBP) formulation that includes a fully integrated autofocus algorithm, i.e. the Factorized Geometrical Autofocus (FGA) algorithm. The base-two factorization is executed in a horizontal plane, using a Merging (M) and a Range History Preserving (RHP) transform. Six parameters are adopted for each sub-aperture pair, i.e. to establish the geometry stage-by-stage via triangles in 3-dimensional space. If the parameters are derived from navigation data, the algorithm is used as a conventional processing chain. If the parameters on the other hand are varied from a certain factorization step and forward, the algorithm is used as a joint image formation and autofocus strategy. By regulating the geometry at multiple resolution levels, challenging defocusing effects, e.g. residual space-variant Range Cell Migration (RCM), can be corrected. The new formulation also serves another important purpose, i.e. as a parameter characterization scheme. By using the FGA algorithm and its inverse, relations between two arbitrary geometries can be studied, in consequence, this makes it feasible to analyze how errors in navigation data, and topography, affect image focus. The versatility of the factorization procedure is demonstrated successfully on simulated Synthetic Aperture Radar (SAR) data. This is achieved by introducing different GPS/IMU errors and Focus Target Plane (FTP) deviations prior to processing. The characterization scheme is then employed to evaluate the sensitivity, to determine at what step the autofocus function should be activated, and to decide the number of necessary parameters at each step. Resulting FGA images are also compared to a reference image (processed without errors and autofocus) and to a defocused image (processed without autofocus), i.e. to validate the novel approach further.},
    doi = {10.1117/12.2050048},
    file = {:torgrimssonDammertHellstenUlanderSPIE2014AutofocusAnalysisGeometricalErrorsFFBackprojection.pdf:PDF},
    keywords = {SAR Processing, Synthetic Aperture Radar, Time-Domain Back-Projection, TDBP, Back-Projection, Autofocus, UWB, VHF, Fast Factorized Back-Projection, FFBP},
    url = {https://doi.org/10.1117/12.2050048},
    
    }
    


  15. Mariantonietta Zonno, Luigi Mascolo, Pietro Guccione, Giovanni Nico, and Andrea Di Pasquale. Impact of focusing of Ground Based SAR data on the quality of interferometric SAR applications. In Proc. of SPIE, volume 9243, pages 1-10, 2014. International Society for Optics and Photonics.
    Abstract: A Ground-Based Synthetic Aperture Radar (GB-SAR) is nowadays employed in several applications. The processing of ground-based, space and airborne SAR data relies on the same physical principles. Nevertheless specific algorithms for the focusing of data acquired by GB-SAR system have been proposed in literature. In this work the impact of the main focusing methods on the interferometric phase dispersion and on the coherence has been studied by employing a real dataset obtained by carrying out an experiment. Several acquisitions of a scene with a corner reflector mounted on a micrometric screw have been made; before some acquisitions the micrometric screw has been displaced of few millimetres in the Line-of-Sight direction. The images have been first focused by using two different algorithms and correspondently, two different sets of interferograms have been generated. The mean and standard deviation of the phase values in correspondence of the corner reflector have been compared to those obtained by knowing the real displacement of the micrometric screw. The mean phase and its dispersion and the coherence values for each focusing algorithm have been quantified and both the precision and the accuracy of the interferometic phase measurements obtained by using the two different focusing methods have been assessed.

    @InProceedings{zonnoMascoloGuccioneNicoDiPasqualeSPIE2014GBSAR,
    author = {Zonno, Mariantonietta and Mascolo, Luigi and Guccione, Pietro and Nico, Giovanni and Di Pasquale, Andrea},
    title = {Impact of focusing of Ground Based SAR data on the quality of interferometric SAR applications},
    booktitle = {Proc. of SPIE},
    year = {2014},
    volume = {9243},
    pages = {1-10},
    organization = {International Society for Optics and Photonics},
    abstract = {A Ground-Based Synthetic Aperture Radar (GB-SAR) is nowadays employed in several applications. The processing of ground-based, space and airborne SAR data relies on the same physical principles. Nevertheless specific algorithms for the focusing of data acquired by GB-SAR system have been proposed in literature. In this work the impact of the main focusing methods on the interferometric phase dispersion and on the coherence has been studied by employing a real dataset obtained by carrying out an experiment. Several acquisitions of a scene with a corner reflector mounted on a micrometric screw have been made; before some acquisitions the micrometric screw has been displaced of few millimetres in the Line-of-Sight direction. The images have been first focused by using two different algorithms and correspondently, two different sets of interferograms have been generated. The mean and standard deviation of the phase values in correspondence of the corner reflector have been compared to those obtained by knowing the real displacement of the micrometric screw. The mean phase and its dispersion and the coherence values for each focusing algorithm have been quantified and both the precision and the accuracy of the interferometic phase measurements obtained by using the two different focusing methods have been assessed.},
    doi = {10.1117/12.2067418},
    file = {:zonnoMascoloGuccioneNicoDiPasqualeSPIE2014GBSAR.pdf:PDF},
    pdf = {../../../docs/zonnoMascoloGuccioneNicoDiPasqualeSPIE2014GBSAR.pdf},
    url = {http://dx.doi.org/10.1117/12.2067418},
    
    }
    


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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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