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Publications of year 2013

Articles in journal or book chapters

  1. Esteban Aguilera, Matteo Nannini, and Andreas Reigber. A Data-Adaptive Compressed Sensing Approach to Polarimetric SAR Tomography of Forested Areas. IEEE Geosci. Remote Sens. Lett., 10(3):543-547, May 2013. Keyword(s): SAR Processing, SAR Tomography, Compressed sensing, Compressive sensing, Covariance matrix, Synthetic aperture radar, Tomography, data compression, forestry, radar polarimetry, tomography, vegetation mapping, wavelet transforms, DLR, E-SAR sensor, German Aerospace Center, covariance fitting, data adaptive compressed sensing approach, data adaptive orthonormal basis, forested areas, fully polarimetric L-band data, multiple looks, multiple polarimetric channels, partial scatterers, polarimetric SAR tomography, superresolution imaging, Distributed compressed sensing (DCS), Kronecker basis, polarimetry, wavelets, E-SAR, F-SAR, L-Band, Airborne SAR.
    Abstract: Super-resolution imaging via compressed sensing (CS)-based spectral estimators has been recently introduced to synthetic aperture radar (SAR) tomography. In the case of partial scatterers, the mainstream has so far been twofold, in that the tomographic reconstruction is conducted by either directly working with multiple looks and/or polarimetric channels or by exploiting the corresponding single-channel second-order statistics. In this letter, we unify these two methodologies in the context of covariance fitting. In essence, we exploit the fact that both vertical structures and the unknown polarimetric signatures can be approximated in a low-dimensional subspace. For this purpose, we make use of a wavelet basis in order to sparsely represent vertical structures. Additionally, we synthesize a data-adaptive orthonormal basis that spans the space of polarimetric signatures. Finally, we validate this approach by using fully polarimetric L-band data acquired by the E-SAR sensor of the German Aerospace Center (DLR).

    @Article{aguileraNanniniReigberGRSL2013,
    author = {Aguilera, Esteban and Nannini, Matteo and Reigber, Andreas},
    title = {A Data-Adaptive Compressed Sensing Approach to Polarimetric {SAR} Tomography of Forested Areas},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2013},
    volume = {10},
    number = {3},
    pages = {543-547},
    month = may,
    issn = {1545-598X},
    abstract = {Super-resolution imaging via compressed sensing (CS)-based spectral estimators has been recently introduced to synthetic aperture radar (SAR) tomography. In the case of partial scatterers, the mainstream has so far been twofold, in that the tomographic reconstruction is conducted by either directly working with multiple looks and/or polarimetric channels or by exploiting the corresponding single-channel second-order statistics. In this letter, we unify these two methodologies in the context of covariance fitting. In essence, we exploit the fact that both vertical structures and the unknown polarimetric signatures can be approximated in a low-dimensional subspace. For this purpose, we make use of a wavelet basis in order to sparsely represent vertical structures. Additionally, we synthesize a data-adaptive orthonormal basis that spans the space of polarimetric signatures. Finally, we validate this approach by using fully polarimetric L-band data acquired by the E-SAR sensor of the German Aerospace Center (DLR).},
    doi = {10.1109/LGRS.2012.2212693},
    file = {:aguileraNanniniReigberGRSL2013.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography,Compressed sensing, Compressive sensing, Covariance matrix, Synthetic aperture radar, Tomography, data compression, forestry, radar polarimetry, tomography, vegetation mapping, wavelet transforms, DLR, E-SAR sensor, German Aerospace Center, covariance fitting, data adaptive compressed sensing approach, data adaptive orthonormal basis, forested areas, fully polarimetric L-band data, multiple looks;multiple polarimetric channels, partial scatterers, polarimetric SAR tomography, superresolution imaging, Distributed compressed sensing (DCS), Kronecker basis, polarimetry,wavelets, E-SAR, F-SAR, L-Band, Airborne SAR},
    pdf = {../../../docs/aguileraNanniniReigberGRSL2013.pdf},
    
    }
    


  2. Esteban Aguilera, Matteo Nannini, and Andreas Reigber. Wavelet-Based Compressed Sensing for SAR Tomography of Forested Areas. IEEE Trans. Geosci. Remote Sens., 51(12):5283-5295, December 2013. Keyword(s): SAR Processing, SAR Tomography, Covariance matrix, Estimation, Power distribution, Sensors, Synthetic aperture radar, Tomography, Wavelet transforms, Compressed sensing (CS), compressive sensing, CS, forest structure, synthetic aperture radar (SAR) tomography, wavelets, E-SAR, F-SAR, L-Band, Airborne SAR.
    Abstract: Synthetic aperture radar (SAR) tomography is a 3-D imaging modality that is commonly tackled by spectral estimation techniques. Thus, the backscattered power along the cross-range direction can be readily obtained by computing the Fourier spectrum of a stack of multibaseline measurements. In addition, recent work has addressed the tomographic inversion under the framework of compressed sensing, thereby recovering sparse cross-range profiles from a reduced set of measurements. This paper differs from previous publications, in that it focuses on sparse expansions in the wavelet domain while working with the second-order statistics of the corresponding multibaseline measurements. In this regard, we elaborate on the conditions under which this perspective is applicable to forested areas and discuss the possibility of optimizing the acquisition geometry. Finally, we compare this approach with traditional nonparametric ones and validate it by using fully polarimetric L-band data acquired by the Experimental SAR (E-SAR) sensor of the German Aerospace Center (DLR).

    @Article{aguileraNanniniReigberTGRS2013CSTomo,
    author = {Aguilera, Esteban and Nannini, Matteo and Reigber, Andreas},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Wavelet-Based Compressed Sensing for {SAR} Tomography of Forested Areas},
    year = {2013},
    issn = {0196-2892},
    month = {dec},
    number = {12},
    pages = {5283--5295},
    volume = {51},
    abstract = {Synthetic aperture radar (SAR) tomography is a 3-D imaging modality that is commonly tackled by spectral estimation techniques. Thus, the backscattered power along the cross-range direction can be readily obtained by computing the Fourier spectrum of a stack of multibaseline measurements. In addition, recent work has addressed the tomographic inversion under the framework of compressed sensing, thereby recovering sparse cross-range profiles from a reduced set of measurements. This paper differs from previous publications, in that it focuses on sparse expansions in the wavelet domain while working with the second-order statistics of the corresponding multibaseline measurements. In this regard, we elaborate on the conditions under which this perspective is applicable to forested areas and discuss the possibility of optimizing the acquisition geometry. Finally, we compare this approach with traditional nonparametric ones and validate it by using fully polarimetric L-band data acquired by the Experimental SAR (E-SAR) sensor of the German Aerospace Center (DLR).},
    doi = {10.1109/TGRS.2012.2231081},
    file = {:aguileraNanniniReigberTGRS2013CSTomo.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Covariance matrix;Estimation;Power distribution;Sensors;Synthetic aperture radar;Tomography;Wavelet transforms;Compressed sensing (CS); compressive sensing, CS, forest structure;synthetic aperture radar (SAR) tomography;wavelets; E-SAR, F-SAR, L-Band, Airborne SAR},
    pdf = {../../../docs/aguileraNanniniReigberTGRS2013CSTomo.pdf},
    publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
    
    }
    


  3. E Bleszynski, M Bleszynski, and T Jaroszewicz. Autofocus algorithm for synthetic aperture radar imaging with large curvilinear apertures. Inverse Problems, 29(5):054004, April 2013. Keyword(s): SAR Processing, Autofocus, Airborne SAR, Gotcha SAR Data.
    Abstract: An approach to autofocusing for large curved synthetic aperture radar (SAR) apertures is presented. Its essential feature is that phase corrections are being extracted not directly from SAR images, but rather from reconstructed SAR phase-history data representing windowed patches of the scene, of sizes sufficiently small to allow the linearization of the forward- and backprojection formulae. The algorithm processes data associated with each patch independently and in two steps. The first step employs a phase-gradient-type method in which phase correction compensating (possibly rapid) trajectory perturbations are estimated from the reconstructed phase history for the dominant scattering point on the patch. The second step uses phase-gradient corrected data and extracts the absolute phase value, removing in thisway phase ambiguities and reducing possible imperfections of the first stage, and providing the distances between the sensor and the scattering point with accuracy comparable to the wavelength. The features of the proposed autofocusing method are illustrated in its applications to intentionally corrupted small-scene 2006 Gotcha data. The examples include the extraction of absolute phases (ranges) for selected prominent point targets. They are then used to focus thescene and determine relative target-target distances.

    @Article{bleszynskiBleszynskiJaroszewiczInverseProblems2013AutofocusForCurvilinearSAR,
    author = {E Bleszynski and M Bleszynski and T Jaroszewicz},
    title = {Autofocus algorithm for synthetic aperture radar imaging with large curvilinear apertures},
    journal = {Inverse Problems},
    year = {2013},
    volume = {29},
    number = {5},
    pages = {054004},
    month = apr,
    abstract = {An approach to autofocusing for large curved synthetic aperture radar (SAR) apertures is presented. Its essential feature is that phase corrections are being extracted not directly from SAR images, but rather from reconstructed SAR phase-history data representing windowed patches of the scene, of sizes sufficiently small to allow the linearization of the forward- and backprojection formulae. The algorithm processes data associated with each patch independently and in two steps. The first step employs a phase-gradient-type method in which phase correction compensating (possibly rapid) trajectory perturbations are estimated from the reconstructed phase history for the dominant scattering point on the patch. The second step uses phase-gradient corrected data and extracts the absolute phase value, removing in thisway phase ambiguities and reducing possible imperfections of the first stage, and providing the distances between the sensor and the scattering point with accuracy comparable to the wavelength. The features of the proposed autofocusing method are illustrated in its applications to intentionally corrupted small-scene 2006 Gotcha data. The examples include the extraction of absolute phases (ranges) for selected prominent point targets. They are then used to focus thescene and determine relative target-target distances.},
    doi = {10.1088/0266-5611/29/5/054004},
    keywords = {SAR Processing, Autofocus, Airborne SAR, Gotcha SAR Data},
    owner = {ofrey},
    publisher = {{IOP} Publishing},
    
    }
    


  4. A. E. Albright Blomberg, A. Austeng, Roy E. Hansen, and S. A. V. Synnes. Improving Sonar Performance in Shallow Water Using Adaptive Beamforming. IEEE Journal of Oceanic Engineering, 38(2):297-307, April 2013. Keyword(s): Synthetic Aperture Sonar, SAS, adaptive signal processing, array signal processing, interference suppression, optimisation, sonar imaging, Hanning window, LCA beamformer, MVDR beamformer, SNR, adaptive beamforming, adaptive minimum variance distortionless response beamformer, bottom-imaging sonars, dense receiver array, four-element receivers, low complexity adaptive beamformer, low sidelobe levels, multipath interference avoidance, multipath propagation, narrow mainlobe width, optimization criteria, second-order multipaths, shallow-water environments, sidelobe suppression, signal-to-noise ratio, sonar performance, spatial smoothing, vertical array, Array signal processing, Arrays, Receivers, Scattering, Sea surface, Signal to noise ratio, Sonar, Adaptive beamforming, multipath reduction, shallow-water imaging, sonar.
    Abstract: Multipath propagation degrades the performance of active, bottom-imaging sonars in shallow-water environments. One way to avoid multipath interference is to use a vertical array with a narrow enough angular response to separate the direct bottom return from the multipath. However, this requires a large array and is often infeasible for practical reasons. In this study, we focus on the use of adaptive beamforming on the receiver side to reduce multipath interference and hence improve the signal-to-noise ratio (SNR). Using a small, dense receiver array, we apply classical and adaptive beamformers to real data collected by the NATO Undersea Research Centre in a shallow-water environment. Our results show that the adaptive minimum variance distortionless response (MVDR) beamformer offers an improvement in the estimated SNR compared to a conventional beamformer in most cases. However, the MVDR beamformer is suboptimal when the receiver consists of only a few elements. We propose using the low complexity adaptive (LCA) beamformer, which is based on the same optimization criteria as the MVDR beamformer, but is robust in a coherent environment without the need for spatial smoothing. For two to 4-element receivers, we observe an improvement of about 0.5-2.5 dB in the estimated SNR when using the LCA beamformer. In cases where the model indicates that the direct bottom return and the dominating multipath arrive from nearly the same angle, little or no improvement is observed. This is typically the case for first- or second-order multipaths reflected off the seafloor toward the receiver. The results from this study also show that with a small vertical array, a narrow mainlobe width is more important than low sidelobe levels, in terms of maximizing the SNR. Consequently, an unweighted conventional beamformer performs better than a conventional beamformer with a Hanning window applied for sidelobe suppression.

    @Article{blombergAustengHansenSynnesJOE2013ImprovingSonarPerformanceUsingAdaptiveBeamforming,
    author = {A. E. Albright Blomberg and A. Austeng and Roy E. Hansen and S. A. V. Synnes},
    title = {Improving Sonar Performance in Shallow Water Using Adaptive Beamforming},
    journal = {IEEE Journal of Oceanic Engineering},
    year = {2013},
    volume = {38},
    number = {2},
    pages = {297-307},
    month = {April},
    issn = {0364-9059},
    abstract = {Multipath propagation degrades the performance of active, bottom-imaging sonars in shallow-water environments. One way to avoid multipath interference is to use a vertical array with a narrow enough angular response to separate the direct bottom return from the multipath. However, this requires a large array and is often infeasible for practical reasons. In this study, we focus on the use of adaptive beamforming on the receiver side to reduce multipath interference and hence improve the signal-to-noise ratio (SNR). Using a small, dense receiver array, we apply classical and adaptive beamformers to real data collected by the NATO Undersea Research Centre in a shallow-water environment. Our results show that the adaptive minimum variance distortionless response (MVDR) beamformer offers an improvement in the estimated SNR compared to a conventional beamformer in most cases. However, the MVDR beamformer is suboptimal when the receiver consists of only a few elements. We propose using the low complexity adaptive (LCA) beamformer, which is based on the same optimization criteria as the MVDR beamformer, but is robust in a coherent environment without the need for spatial smoothing. For two to 4-element receivers, we observe an improvement of about 0.5-2.5 dB in the estimated SNR when using the LCA beamformer. In cases where the model indicates that the direct bottom return and the dominating multipath arrive from nearly the same angle, little or no improvement is observed. This is typically the case for first- or second-order multipaths reflected off the seafloor toward the receiver. The results from this study also show that with a small vertical array, a narrow mainlobe width is more important than low sidelobe levels, in terms of maximizing the SNR. Consequently, an unweighted conventional beamformer performs better than a conventional beamformer with a Hanning window applied for sidelobe suppression.},
    doi = {10.1109/JOE.2012.2226643},
    file = {:blombergAustengHansenSynnesJOE2013ImprovingSonarPerformanceUsingAdaptiveBeamforming.pdf:PDF},
    keywords = {Synthetic Aperture Sonar, SAS,adaptive signal processing;array signal processing;interference suppression;optimisation;sonar imaging;Hanning window;LCA beamformer;MVDR beamformer;SNR;adaptive beamforming;adaptive minimum variance distortionless response beamformer;bottom-imaging sonars;dense receiver array;four-element receivers;low complexity adaptive beamformer;low sidelobe levels;multipath interference avoidance;multipath propagation;narrow mainlobe width;optimization criteria;second-order multipaths;shallow-water environments;sidelobe suppression;signal-to-noise ratio;sonar performance;spatial smoothing;vertical array;Array signal processing;Arrays;Receivers;Scattering;Sea surface;Signal to noise ratio;Sonar;Adaptive beamforming;multipath reduction;shallow-water imaging;sonar},
    
    }
    


  5. A. E. A. Blomberg, C. I. C. Nilsen, A. Austeng, and Roy E. Hansen. Adaptive Sonar Imaging Using Aperture Coherence. IEEE Journal of Oceanic Engineering, 38(1):98-108, January 2013. Keyword(s): Synthetic Aperture Sonar, SAS, array signal processing, sonar imaging, speckle, DAS beamformer, HISAS 1030 sonar, SNR scenarios, SWiP, Wiener postfilter, adaptive sonar imaging, aperture-coherence-based methods, backscattered energy, coherence factor, computationally efficient adaptive imaging methods, delay-and-sum beamformer, image resolution, medical ultrasound imaging, noise suppression capabilities, receiver array, signal-to-noise ratio, speckle environment, Apertures, Arrays, Coherence, Imaging, Noise, Sonar, Speckle, Adaptive beamforming, Wiener postfilter, aperture coherence, array signal gain, coherence factor (CF), sonar imaging.
    Abstract: A class of computationally efficient adaptive imaging methods originating from the coherence factor (CF) has been proposed for improved medical ultrasound imaging. These methods are based on the idea that when steering the receiver toward a point of interest, the backscattered energy from this point exhibits a high degree of aperture coherence, while random noise, multipath interference, and sidelobe energy do not. Aperture coherence can be understood as a normalized measure of the degree of signal variability across the receiver array. This paper presents a study of the use of aperture-coherence-based methods for improved sonar imaging, with particular emphasis on a recently introduced robust implementation known as the scaled Wiener postfilter (SWiP). We show that while the CF has strong noise suppression capabilities and performs well on point targets, it lacks robustness in low signal-to-noise ratio (SNR) scenarios and introduces undesirable artifacts in speckle scenes. The SWiP is closely related to the CF, but contains a single-user-defined parameter, which allows the method to be tuned to suit the application needs. The SWiP can be tuned to offer robustness in a speckle environment such as when imaging the seafloor, or for strong noise suppression capabilities. This makes it a promising method for a wide range of sonar applications. We base our conclusions on simulated data from a constructed speckle scene as well as experimental data from the SX90 fish-finding sonar and sidescan data from the HISAS 1030 sonar. Our results show that the SWiP offers improved edge and shadow definitions and reduced sidelobe levels when compared to the conventional delay-and-sum (DAS) beamformer. These improvements do not compromise the image resolution, and they come at a low computational cost.

    @Article{blombergNilsenAustengHansenJOE2013AdaptiveSonarUsingApertureCoherence,
    author = {A. E. A. Blomberg and C. I. C. Nilsen and A. Austeng and Roy E. Hansen},
    title = {Adaptive Sonar Imaging Using Aperture Coherence},
    journal = {IEEE Journal of Oceanic Engineering},
    year = {2013},
    volume = {38},
    number = {1},
    pages = {98-108},
    month = {Jan},
    issn = {0364-9059},
    abstract = {A class of computationally efficient adaptive imaging methods originating from the coherence factor (CF) has been proposed for improved medical ultrasound imaging. These methods are based on the idea that when steering the receiver toward a point of interest, the backscattered energy from this point exhibits a high degree of aperture coherence, while random noise, multipath interference, and sidelobe energy do not. Aperture coherence can be understood as a normalized measure of the degree of signal variability across the receiver array. This paper presents a study of the use of aperture-coherence-based methods for improved sonar imaging, with particular emphasis on a recently introduced robust implementation known as the scaled Wiener postfilter (SWiP). We show that while the CF has strong noise suppression capabilities and performs well on point targets, it lacks robustness in low signal-to-noise ratio (SNR) scenarios and introduces undesirable artifacts in speckle scenes. The SWiP is closely related to the CF, but contains a single-user-defined parameter, which allows the method to be tuned to suit the application needs. The SWiP can be tuned to offer robustness in a speckle environment such as when imaging the seafloor, or for strong noise suppression capabilities. This makes it a promising method for a wide range of sonar applications. We base our conclusions on simulated data from a constructed speckle scene as well as experimental data from the SX90 fish-finding sonar and sidescan data from the HISAS 1030 sonar. Our results show that the SWiP offers improved edge and shadow definitions and reduced sidelobe levels when compared to the conventional delay-and-sum (DAS) beamformer. These improvements do not compromise the image resolution, and they come at a low computational cost.},
    doi = {10.1109/JOE.2012.2210295},
    file = {:blombergNilsenAustengHansenJOE2013AdaptiveSonarUsingApertureCoherence.pdf:PDF},
    keywords = {Synthetic Aperture Sonar, SAS, array signal processing;sonar imaging;speckle;DAS beamformer;HISAS 1030 sonar;SNR scenarios;SWiP;Wiener postfilter;adaptive sonar imaging;aperture-coherence-based methods;backscattered energy;coherence factor;computationally efficient adaptive imaging methods;delay-and-sum beamformer;image resolution;medical ultrasound imaging;noise suppression capabilities;receiver array;signal-to-noise ratio;speckle environment;Apertures;Arrays;Coherence;Imaging;Noise;Sonar;Speckle;Adaptive beamforming;Wiener postfilter;aperture coherence;array signal gain;coherence factor (CF);sonar imaging},
    
    }
    


  6. F. Bovenga, V.M. Giacovazzo, A. Refice, and N. Veneziani. Multichromatic Analysis of InSAR Data. IEEE Trans. Geosci. Remote Sens., 51(9):4790-4799, September 2013. Keyword(s): SAR Processing, airborne radar, geophysical image processing, radar imaging, radar interferometry, remote sensing by radar, synthetic aperture radar, AES-1 airborne sensor, InSAR data multichromatic analysis, MCA absolute phase measurement, MCA experimental validation, MCA processing parameters, absolute optical path difference inference, central carrier frequency, height estimation performance, height information retrieval, interferometric SAR image pairs, parametric analysis, pixel phase trend, spatial phase unwrapping, wideband SAR single pass interferometric data set, Accuracy, Bandwidth, Distance measurement, Estimation, Noise, Synthetic aperture radar, Thyristors, synthetic aperture radar interferometry (InSAR).
    Abstract: The multichromatic analysis (MCA) uses interferometric pairs of SAR images processed at range subbands and explores the phase trend of each pixel as a function of the different central carrier frequencies to infer absolute optical path difference. This approach allows retrieving unambiguous height information on selected pixels, potentially solving the problem of spatial phase unwrapping, which is instead critical in the standard monochromatic processing. The method, based on concepts originally introduced by Madsen and Zebker, has been developed in previous work both theoretically and through simulations. This paper presents the first MCA experimental validation of the procedure, through application to a wideband SAR single-pass interferometric data set acquired by the AES-1 airborne sensor. An evaluation of the impact of the MCA processing parameters on the height estimation performances is obtained through a parametric analysis. The results confirm the indications derived by the theoretical analysis, demonstrating the feasibility of the MCA absolute phase measurement, provided that a sufficient bandwidth is available.

    @Article{bovengaGiacovazzoReficeVenezianiTGRS2013,
    author = {Bovenga, F. and Giacovazzo, V.M. and Refice, A. and Veneziani, N.},
    title = {Multichromatic Analysis of {InSAR} Data},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2013},
    volume = {51},
    number = {9},
    pages = {4790-4799},
    month = sep,
    issn = {0196-2892},
    abstract = {The multichromatic analysis (MCA) uses interferometric pairs of SAR images processed at range subbands and explores the phase trend of each pixel as a function of the different central carrier frequencies to infer absolute optical path difference. This approach allows retrieving unambiguous height information on selected pixels, potentially solving the problem of spatial phase unwrapping, which is instead critical in the standard monochromatic processing. The method, based on concepts originally introduced by Madsen and Zebker, has been developed in previous work both theoretically and through simulations. This paper presents the first MCA experimental validation of the procedure, through application to a wideband SAR single-pass interferometric data set acquired by the AES-1 airborne sensor. An evaluation of the impact of the MCA processing parameters on the height estimation performances is obtained through a parametric analysis. The results confirm the indications derived by the theoretical analysis, demonstrating the feasibility of the MCA absolute phase measurement, provided that a sufficient bandwidth is available.},
    doi = {10.1109/TGRS.2012.2230633},
    file = {:bovengaGiacovazzoReficeVenezianiTGRS2013.pdf:PDF},
    keywords = {SAR Processing, airborne radar;geophysical image processing;radar imaging;radar interferometry;remote sensing by radar;synthetic aperture radar;AES-1 airborne sensor;InSAR data multichromatic analysis;MCA absolute phase measurement;MCA experimental validation;MCA processing parameters;absolute optical path difference inference;central carrier frequency;height estimation performance;height information retrieval;interferometric SAR image pairs;parametric analysis;pixel phase trend;spatial phase unwrapping;wideband SAR single pass interferometric data set;Accuracy;Bandwidth;Distance measurement;Estimation;Noise;Synthetic aperture radar;Thyristors;synthetic aperture radar interferometry (InSAR)},
    pdf = {../../../docs/bovengaGiacovazzoReficeVenezianiTGRS2013.pdf},
    
    }
    


  7. A. Capozzoli, C. Curcio, and A. Liseno. FAST GPU-BASED INTERPOLATION FOR SAR BACKPROJECTION. Progress In Electromagnetics Research, 133:259-283, 2013. Keyword(s): SAR Processsing, Time-Domain Back-Projection, TDBP, Back-Projection, Non-Uniform FFT, NUFFT, CUDA, GPU, NVIDIA, Parallelized Processing, Synthetic Aperture Radar (SAR), motion compensation, Airborne SAR, Topography-dependent motion compensation, Motion Compensation, MoComp.
    Abstract: We introduce and discuss a parallel SAR backprojection algorithm using a Non-Uniform FFT (NUFFT) routine implemented on a GPU in CUDA language. The details of a convenient GPU implementation of the NUFFT-based SAR backprojection algorithm, amenable to further generalizations to a multi-GPU architecture, are also given. The performance of the approach is analyzed in terms of accuracy and computational speed by comparisons to a ``standard'', parallel version of the backprojection algorithm exploiting FFT+interpolation instead of the NUFFT. Different interpolators have been considered for the latter processing scheme. The NUFFT-based backprojection has proven significantly more accurate than all the compared approach, with a computing time of the same order. An analysis of the computational burden of all the different steps involved in both the considered approaches (i.e., standard and NUFFT backprojections) has been also reported. Experimental results against the Air Force Research Laboratory (AFRL) airborne data delivered under the ``challenge problem for SAR-based Ground Moving Target Identification (GMTI) in urban environments" and collected over circular flight paths are also shown.

    @Article{capozzoliCurcioLisenoPIER2013CUDAGPUBackprojection,
    author = {A. Capozzoli and C. Curcio and A. Liseno},
    title = {FAST GPU-BASED INTERPOLATION FOR SAR BACKPROJECTION},
    journal = {Progress In Electromagnetics Research},
    year = {2013},
    volume = {133},
    pages = {259-283},
    doi = {10.2528/PIER12071909},
    abstract = {We introduce and discuss a parallel SAR backprojection algorithm using a Non-Uniform FFT (NUFFT) routine implemented on a GPU in CUDA language. The details of a convenient GPU implementation of the NUFFT-based SAR backprojection algorithm, amenable to further generalizations to a multi-GPU architecture, are also given. The performance of the approach is analyzed in terms of accuracy and computational speed by comparisons to a ``standard'', parallel version of the backprojection algorithm exploiting FFT+interpolation instead of the NUFFT. Different interpolators have been considered for the latter processing scheme. The NUFFT-based backprojection has proven significantly more accurate than all the compared approach, with a computing time of the same order. An analysis of the computational burden of all the different steps involved in both the considered approaches (i.e., standard and NUFFT backprojections) has been also reported. Experimental results against the Air Force Research Laboratory (AFRL) airborne data delivered under the ``challenge problem for SAR-based Ground Moving Target Identification (GMTI) in urban environments" and collected over circular flight paths are also shown.}, keywords = {SAR Processsing, Time-Domain Back-Projection, TDBP, Back-Projection, Non-Uniform FFT, NUFFT, CUDA, GPU, NVIDIA, Parallelized Processing, Synthetic Aperture Radar (SAR), motion compensation, Airborne SAR, Topography-dependent motion compensation, Motion Compensation, MoComp}, owner = {ofrey}, pdf = {../../../docs/capozzoliCurcioLisenoPIER2013CUDAGPUBackprojection.pdf}, 
    }
    


  8. Michele Crosetto, J. A. Gili, Oriol Monserrat, M. Cuevas-González, J. Corominas, and D. Serral. Interferometric SAR monitoring of the Vallcebre landslide (Spain) using corner reflectors. Natural Hazards and Earth System Sciences, 13(4):923-933, 2013.
    @Article{crosettoGiliMonserratCuevasGonzalezCorominasSerral2013InSARLandslide,
    author = {Crosetto, Michele and Gili, J. A. and Monserrat, Oriol and Cuevas-Gonz{\'a}lez, M. and Corominas, J. and Serral, D.},
    title = {Interferometric {SAR} monitoring of the {Vallcebre} landslide ({Spain}) using corner reflectors},
    journal = {Natural Hazards and Earth System Sciences},
    year = {2013},
    volume = {13},
    number = {4},
    pages = {923--933},
    owner = {ofrey},
    publisher = {Copernicus GmbH},
    
    }
    


  9. Francesco De Zan, Gerhard Krieger, and Paco López-Dekker. On Some Spectral Properties of TanDEM-X Interferograms Over Forested Areas. IEEE Geoscience and Remote Sensing Letters, 10(1):71-75, January 2013. Keyword(s): Analytical models, Coherence, Interferometry, Predictive models, Remote sensing, Synthetic aperture radar, Synthetic aperture radar (SAR) interferometry, Tandem-X.
    Abstract: This letter reports about some observations over rainforests (in Brazil and Indonesia), where the spectra of TanDEM-X interferograms show distinct features, almost a signature, which is explained and modeled in terms of the scattering properties. Supported by comparisons with simulations, the observations exclude any homogeneous horizontally layered forest; instead, they are compatible with a model with point scatterers clustered in clouds. Such a model, with high extinction and large gaps that allow significant penetration, is able to explain to a good degree the observations.

    @Article{deZanKriegerLopezDekkerGRSL2013TandemXCoherence,
    author = {De Zan, Francesco and Krieger, Gerhard and L\'opez-Dekker, Paco},
    title = {On Some Spectral Properties of {TanDEM-X} Interferograms Over Forested Areas},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    year = {2013},
    volume = {10},
    number = {1},
    pages = {71-75},
    month = jan,
    issn = {1545-598X},
    abstract = {This letter reports about some observations over rainforests (in Brazil and Indonesia), where the spectra of TanDEM-X interferograms show distinct features, almost a signature, which is explained and modeled in terms of the scattering properties. Supported by comparisons with simulations, the observations exclude any homogeneous horizontally layered forest; instead, they are compatible with a model with point scatterers clustered in clouds. Such a model, with high extinction and large gaps that allow significant penetration, is able to explain to a good degree the observations.},
    doi = {10.1109/LGRS.2012.2193114},
    file = {:deZanKriegerLopezDekkerGRSL2013TandemXCoherence.pdf:PDF},
    keywords = {Analytical models;Coherence;Interferometry;Predictive models;Remote sensing;Synthetic aperture radar;Synthetic aperture radar (SAR) interferometry, Tandem-X},
    owner = {ofrey},
    pdf = {../../../docs/deZanKriegerLopezDekkerGRSL2013TandemXCoherence.pdf},
    
    }
    


  10. A. Elsherbini and K. Sarabandi. ENVELOP Antenna: A Class of Very Low Profile UWB Directive Antennas for Radar and Communication Diversity Applications. IEEE_J_AP, 61(3):1055-1062, March 2013. Keyword(s): airborne radar, dipole antennas, directive antennas, diversity reception, horn antennas, magnetic moments, radar antennas, ultra wideband antennas, ultra wideband communication, ENVELOP antenna, airborne radars, antenna radiation characteristics, communication diversity application, crossed electric dipole, impedance matching performance, inductive loop antenna, magnetic dipoles, polarization diversity, radar application, sheet loop, short TEM horn, very low profile UWB directive antenna, Antenna radiation patterns, Bandwidth, Directive antennas, Horn antennas, Radar antennas, Ultra wideband antennas, Monopole antenna, UWB antenna, radar antenna.
    @Article{Elsherbini2013,
    author = {A. Elsherbini and K. Sarabandi},
    title = {ENVELOP Antenna: A Class of Very Low Profile {UWB} Directive Antennas for Radar and Communication Diversity Applications},
    journal = IEEE_J_AP,
    year = {2013},
    volume = {61},
    number = {3},
    month = mar,
    pages = {1055--1062},
    issn = {0018-926X},
    doi = {10.1109/TAP.2012.2229951},
    keywords = {airborne radar, dipole antennas, directive antennas, diversity reception, horn antennas, magnetic moments, radar antennas, ultra wideband antennas, ultra wideband communication, ENVELOP antenna, airborne radars, antenna radiation characteristics, communication diversity application, crossed electric dipole, impedance matching performance, inductive loop antenna, magnetic dipoles, polarization diversity, radar application, sheet loop, short TEM horn, very low profile UWB directive antenna, Antenna radiation patterns, Bandwidth, Directive antennas, Horn antennas, Radar antennas, Ultra wideband antennas, Monopole antenna, UWB antenna, radar antenna},
    owner = {ofrey},
    
    }
    


  11. Gianfranco Fornaro, Diego Reale, and Simona Verde. Bridge Thermal Dilation Monitoring With Millimeter Sensitivity via Multidimensional SAR Imaging. IEEE Geosci. Remote Sens. Lett., 10(4):677-681, July 2013. Keyword(s): SAR Processing, SAR interferometry, Interferometry, differential interferometry, InSAR, DInSAR, Persistent Scatterer Interferometry, PSI, SAR Tomography, Tomography, Spaceborne SAR, TerraSAR-X, X-band, Bridges, Imaging, Interferometry, Monitoring, Remote sensing, Synthetic aperture radar, Temperature measurement, geophysical techniques, radar imaging, remote sensing by radar, synthetic aperture radar, Italy, Musmeci bridge, Potenza, SAR processing chains, SAR sensors, TerraSAR-X data set, accurate monitoring capabilities, bridge static structure, bridge thermal dilation monitoring, interferometric approaches, man-made structures, millimeter sensitivity, multidimensional SAR imaging, multidimensional imaging approach, spatial resolution, synthetic aperture radar, system sensitivity, thermal coefficient, Multidimensional SAR imaging (MDI-SAR), SAR tomography, TerraSAR-X (TSX), synthetic aperture radar (SAR), thermal dilation;.
    Abstract: The new generation of synthetic aperture radar (SAR) sensors is providing images with very high spatial resolution, improved up to the meter scale. Such a resolution increase allows more accurate monitoring capabilities by means of interferometric approaches. The use of higher frequency enhances the sensitivity of the system even to minute changes, such as thermal dilations. This phenomenon has an impact on the interferometric products, particularly on the deformation velocity maps, if not properly handled. Man-made structures, such as steel core bridges and specific buildings, may be very sensible to thermal dilation effects. By extending the multitemporal differential interferometry SAR processing chains, in our case based on the multidimensional imaging (MDI) approach, an additional parameter related to temperature differences at acquisition instants, the thermal coefficient, can be accurately estimated. This parameter provides interesting perspectives in application to infrastructure monitoring: It brings information about the thermal behavior of the imaged objects. In this letter, we investigate the thermal response of the Musmeci bridge (Potenza, Italy), by experimenting the extended MDI approach on a real TerraSAR-X data set. Results highlight the possibility of such a technique to obtain measurements of the motion that is highly correlated with temperature, thus providing useful information about the static structure of bridges.

    @Article{fornaroRealeVerdeGRSL2013,
    author = {Fornaro, Gianfranco and Reale, Diego and Verde, Simona},
    title = {Bridge Thermal Dilation Monitoring With Millimeter Sensitivity via Multidimensional {SAR} Imaging},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2013},
    volume = {10},
    number = {4},
    pages = {677-681},
    month = jul,
    issn = {1545-598X},
    abstract = {The new generation of synthetic aperture radar (SAR) sensors is providing images with very high spatial resolution, improved up to the meter scale. Such a resolution increase allows more accurate monitoring capabilities by means of interferometric approaches. The use of higher frequency enhances the sensitivity of the system even to minute changes, such as thermal dilations. This phenomenon has an impact on the interferometric products, particularly on the deformation velocity maps, if not properly handled. Man-made structures, such as steel core bridges and specific buildings, may be very sensible to thermal dilation effects. By extending the multitemporal differential interferometry SAR processing chains, in our case based on the multidimensional imaging (MDI) approach, an additional parameter related to temperature differences at acquisition instants, the thermal coefficient, can be accurately estimated. This parameter provides interesting perspectives in application to infrastructure monitoring: It brings information about the thermal behavior of the imaged objects. In this letter, we investigate the thermal response of the Musmeci bridge (Potenza, Italy), by experimenting the extended MDI approach on a real TerraSAR-X data set. Results highlight the possibility of such a technique to obtain measurements of the motion that is highly correlated with temperature, thus providing useful information about the static structure of bridges.},
    doi = {10.1109/LGRS.2012.2218214},
    file = {:fornaroRealeVerdeGRSL2013.pdf:PDF},
    keywords = {SAR Processing, SAR interferometry, Interferometry, differential interferometry, InSAR, DInSAR,Persistent Scatterer Interferometry, PSI, SAR Tomography, Tomography,Spaceborne SAR, TerraSAR-X,X-band,Bridges;Imaging;Interferometry;Monitoring;Remote sensing;Synthetic aperture radar;Temperature measurement;geophysical techniques;radar imaging;remote sensing by radar;synthetic aperture radar;Italy;Musmeci bridge;Potenza;SAR processing chains;SAR sensors;TerraSAR-X data set;accurate monitoring capabilities;bridge static structure;bridge thermal dilation monitoring;interferometric approaches;man-made structures;millimeter sensitivity;multidimensional SAR imaging;multidimensional imaging approach;spatial resolution;synthetic aperture radar;system sensitivity;thermal coefficient;Multidimensional SAR imaging (MDI-SAR);SAR tomography;TerraSAR-X (TSX);synthetic aperture radar (SAR);thermal dilation;},
    pdf = {../../../docs/fornaroRealeVerdeGRSL2013.pdf},
    
    }
    


  12. Othmar Frey, Maurizio Santoro, Charles L. Werner, and Urs Wegmuller. DEM-based SAR pixel area estimation for enhanced geocoding refinement and radiometric normalization. IEEE Geosci. Remote Sens. Lett., 10(1):48-52, January 2013. Keyword(s): SAR Processing, Geocoding, radiometric calibration, terrain-based radiometric normalization.
    Abstract: Precise terrain-corrected georeferencing of synthetic aperture radar (SAR) images and derived products in range-Doppler coordinates is important with respect to several aspects, such as data interpretation, combination with other geodata products, and transformation of, e.g., terrain heights into SAR geometry as used in differential interferometric SAR (DInSAR) applications. For georeferencing, a lookup table is calculated and then refined based on a coregistration of the actual SAR image to a simulated SAR image. The impact of using two different implementations of such a simulator of topography-induced radar brightness, 1) an approach based on angular relationships and 2) a pixel-area-based method, is discussed in this letter. It is found that the pixel-area-based method leads to considerable improvements with regard to the robustness of georeferencing and also with regard to radiometric normalization in layover-affected areas.

    @Article{freySantoroWegmullerWernerGRSL2012,
    author = {Othmar Frey and Maurizio Santoro and Charles L. Werner and Urs Wegmuller},
    title = {{DEM}-based {SAR} pixel area estimation for enhanced geocoding refinement and radiometric normalization},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2013},
    volume = {10},
    number = {1},
    pages = {48-52},
    month = jan,
    abstract = {Precise terrain-corrected georeferencing of synthetic aperture radar (SAR) images and derived products in range-Doppler coordinates is important with respect to several aspects, such as data interpretation, combination with other geodata products, and transformation of, e.g., terrain heights into SAR geometry as used in differential interferometric SAR (DInSAR) applications. For georeferencing, a lookup table is calculated and then refined based on a coregistration of the actual SAR image to a simulated SAR image. The impact of using two different implementations of such a simulator of topography-induced radar brightness, 1) an approach based on angular relationships and 2) a pixel-area-based method, is discussed in this letter. It is found that the pixel-area-based method leads to considerable improvements with regard to the robustness of georeferencing and also with regard to radiometric normalization in layover-affected areas.},
    doi = {10.1109/LGRS.2012.2192093},
    file = {:freySantoroWegmullerWernerGRSL2012.pdf:PDF},
    keywords = {SAR Processing, Geocoding, radiometric calibration, terrain-based radiometric normalization},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freySantoroWernerWegmullerGRSL2012.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6194993},
    
    }
    


  13. Ruben Iglesias and Jordi J. Mallorqui. Side-Lobe Cancelation in DInSAR Pixel Selection With SVA. IEEE Geosci. Remote Sens. Lett., 10(4):667-671, 2013. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, DInSAR, Differential Interferometry, geophysical image processing, geophysical techniques, image enhancement, radar imaging, synthetic aperture radar, DInSAR pixel selection algorithm, SAR images, SAR systems, SVA filtering, amplitude stability, bidimensional sinc function shape, complex data, complex scattering scenarios, cosine-on-pedestal weighting functions, differential interferometric synthetic aperture radar, nonlinear filter, original image resolution, pixel cluster, pixel position, point spread function, resolution enhancement, side-lobe cancelation, single cell, spatially variant apodization, strong scatterer main lobe, strong scatterer side lobe, synthetic aperture radar, total side-lobe cancelation, Azimuth, Dispersion, Image resolution, Indexes, Interferometry, Standards, Synthetic aperture radar, Differential interferometric synthetic aperture radar (SAR) (DInSAR), SAR, interferometry, spatially variant apodization (SVA).
    Abstract: Synthetic aperture radar (SAR) systems are inherently band limited in both range and azimuth, and hence, the point spread function (PSF) has the shape of a bidimensional sinc function. In addition, all SAR images are slightly oversampled, and as a consequence, the contribution of a single target extends to more than a single cell. The main lobe and the side lobes of strong scatterers are sometimes clearly visible in the images. This characteristic of the SAR images must be considered when applying differential interferometric synthetic aperture radar (DInSAR) pixel selection algorithms. For persistent scatterers, the properties, for instance, the amplitude stability, are preserved in both redundant information around the main lobe and side lobes. For this reason, a cluster of pixels rather than just the pixel position corresponding to the exact location of the target will be detected. Spatially variant apodization (SVA) is a nonlinear filter based on cosine-on-pedestal weighting functions able to achieve a total side-lobe cancelation without degrading the original image resolution. When working with complex data under complex scattering scenarios, the PSF moves away from the ideal bidimensional sinc, and the SVA performance worsens. The amplitude and phase of the original images could be distorted by the SVA filtering compromising the pixel selection and the quality of the final DInSAR results. In this letter, SVA is used to method locate in the image the side lobes of high-power scatterers and generate a mask while preserving the amplitude and phase of the original images.

    @Article{iglesiasMallorqui2013GRSLPSISVA,
    author = {Iglesias, Ruben and Mallorqui, Jordi J.},
    title = {Side-Lobe Cancelation in {DInSAR} Pixel Selection With {SVA}},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2013},
    volume = {10},
    number = {4},
    pages = {667-671},
    issn = {1545-598X},
    abstract = {Synthetic aperture radar (SAR) systems are inherently band limited in both range and azimuth, and hence, the point spread function (PSF) has the shape of a bidimensional sinc function. In addition, all SAR images are slightly oversampled, and as a consequence, the contribution of a single target extends to more than a single cell. The main lobe and the side lobes of strong scatterers are sometimes clearly visible in the images. This characteristic of the SAR images must be considered when applying differential interferometric synthetic aperture radar (DInSAR) pixel selection algorithms. For persistent scatterers, the properties, for instance, the amplitude stability, are preserved in both redundant information around the main lobe and side lobes. For this reason, a cluster of pixels rather than just the pixel position corresponding to the exact location of the target will be detected. Spatially variant apodization (SVA) is a nonlinear filter based on cosine-on-pedestal weighting functions able to achieve a total side-lobe cancelation without degrading the original image resolution. When working with complex data under complex scattering scenarios, the PSF moves away from the ideal bidimensional sinc, and the SVA performance worsens. The amplitude and phase of the original images could be distorted by the SVA filtering compromising the pixel selection and the quality of the final DInSAR results. In this letter, SVA is used to method locate in the image the side lobes of high-power scatterers and generate a mask while preserving the amplitude and phase of the original images.},
    doi = {10.1109/LGRS.2012.2217935},
    file = {:iglesiasMallorqui2013GRSLPSISVA.pdf:PDF},
    keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI, DInSAR, Differential Interferometry, geophysical image processing;geophysical techniques;image enhancement;radar imaging;synthetic aperture radar; DInSAR pixel selection algorithm;SAR images;SAR systems;SVA filtering;amplitude stability; bidimensional sinc function shape;complex data;complex scattering scenarios;cosine-on-pedestal weighting functions; differential interferometric synthetic aperture radar;nonlinear filter;original image resolution;pixel cluster; pixel position;point spread function;resolution enhancement;side-lobe cancelation;single cell; spatially variant apodization;strong scatterer main lobe;strong scatterer side lobe;synthetic aperture radar; total side-lobe cancelation;Azimuth;Dispersion;Image resolution;Indexes;Interferometry;Standards;Synthetic aperture radar; Differential interferometric synthetic aperture radar (SAR) (DInSAR);SAR;interferometry;spatially variant apodization (SVA)},
    owner = {ofrey},
    pdf = {../../../docs/iglesiasMallorqui2013GRSLPSISVA.pdf},
    
    }
    


  14. J.M.L. King, R. Kelly, A. Kasurak, C. Duguay, G. Gunn, and J.B. Mead. UW-Scat: A Ground-Based Dual-Frequency Scatterometer for Observation of Snow Properties. IEEE Geosci. Remote Sens. Lett., 10(3):528-532, May 2013. Keyword(s): geophysical equipment, snow, AD 2009 to 2011, Canada, Canadian Subarctic, Churchill, UW-Scat scatterometer, University of Waterloo scatterometer, angular width, azimuth user-programmable range, elevation angle, frequency 17.2 GHz, frequency 9.6 GHz, frequency-modulated continuous-wave radars, ground-based dual-frequency scatterometer, harsh environmental conditions, ice property observation, radar beam, snow property observation, terrestrial snow, two-axis positioning system, Backscatter, Calibration, Ice, Radar measurements, Radio frequency, Snow, Spaceborne radar, Radar polarimetry, scatterometer, snow.
    Abstract: The University of Waterloo scatterometer, which is a system developed for observation of snow and ice properties, is described. The system is composed of two frequency-modulated continuous-wave radars operating at center frequencies of 17.2 and 9.6 GHz. A field-deployable platform allows a rapid setup and observation at remote sites under harsh environmental conditions. A two-axis positioning system moves the radar beam across a user-programmable range of azimuth (+/-180 deg) and elevation angles (15-105 deg). Typical azimuth scans of 60deg angular width generate between 21 and 586 independent samples, depending on the wavelength and the elevation angle. The backscatter response of terrestrial snow in the Canadian Subarctic is demonstrated with two experiments conducted in Churchill, MB, Canada, between 2009 and 2011.

    @Article{kingKellyKasurakDuguayGunnMeadGRSL2013XandKuScatSnow,
    author = {King, J.M.L. and Kelly, R. and Kasurak, A. and Duguay, C. and Gunn, G. and Mead, J.B.},
    title = {{UW-Scat}: A Ground-Based Dual-Frequency Scatterometer for Observation of Snow Properties},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2013},
    volume = {10},
    number = {3},
    pages = {528-532},
    month = may,
    issn = {1545-598X},
    abstract = {The University of Waterloo scatterometer, which is a system developed for observation of snow and ice properties, is described. The system is composed of two frequency-modulated continuous-wave radars operating at center frequencies of 17.2 and 9.6 GHz. A field-deployable platform allows a rapid setup and observation at remote sites under harsh environmental conditions. A two-axis positioning system moves the radar beam across a user-programmable range of azimuth (+/-180 deg) and elevation angles (15-105 deg). Typical azimuth scans of 60deg angular width generate between 21 and 586 independent samples, depending on the wavelength and the elevation angle. The backscatter response of terrestrial snow in the Canadian Subarctic is demonstrated with two experiments conducted in Churchill, MB, Canada, between 2009 and 2011.},
    doi = {10.1109/LGRS.2012.2212177},
    file = {:kingKellyKasurakDuguayGunnMeadGRSL2013XandKuScatSnow.pdf:PDF},
    keywords = {geophysical equipment;snow;AD 2009 to 2011;Canada;Canadian Subarctic;Churchill;UW-Scat scatterometer;University of Waterloo scatterometer;angular width;azimuth user-programmable range;elevation angle;frequency 17.2 GHz;frequency 9.6 GHz;frequency-modulated continuous-wave radars;ground-based dual-frequency scatterometer;harsh environmental conditions;ice property observation;radar beam;snow property observation;terrestrial snow;two-axis positioning system;Backscatter;Calibration;Ice;Radar measurements;Radio frequency;Snow;Spaceborne radar;Radar polarimetry;scatterometer;snow},
    pdf = {../../../docs/kingKellyKasurakDuguayGunnMeadGRSL2013XandKuScatSnow.pdf},
    
    }
    


  15. Seung-Kuk Lee, Florian Kugler, Konstantinos P. Papathanassiou, and Irena Hajnsek. Quantification of Temporal Decorrelation Effects at L-Band for Polarimetric SAR Interferometry Applications. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 6(3):1351-1367, June 2013. Keyword(s): SAR Processing, Decorrelation, Temporal Decorrelation, airborne radar, data acquisition, decorrelation, estimation theory, radar polarimetry, spaceborne radar, synthetic aperture radar, BioSAR 2007, L-band E-SAR repeat-pass data acquisition, Pol-InSAR forest parameter inversion, TempoSAR 2008, TempoSAR 2009, ground temporal decorrelation effect, height inversion error, interferometric repeat-pass mode, multibaseline Pol-InSAR data acquisition, polarimetric SAR interferometry application, quantitative estimation, rain-induced dielectric change, satellite airborne SAR system, temporal baseline estimation, time 10 min to 54 day, velocity 2 m/s, volume temporal decorrelation effect, Height inversion, polarimetric synthetic aperture radar interferometry (Pol-InSAR), temporal baseline, temporal decorrelation.
    Abstract: Temporal decorrelation is the most critical issue for the successful inversion of polarimetric SAR interferometry (Pol-InSAR) data acquired in an interferometric repeat-pass mode, typical for satellite or lower frequency airborne SAR systems. This paper provides a quantitative estimation of temporal decorrelation effects at L-band for a wide range of temporal baselines based on a unique set of multibaseline Pol-InSAR data. A new methodology that allows to quantify individual temporal decorrelation components has been developed and applied. Temporal decorrelation coefficients are estimated for temporal baselines ranging from 10 min to 54 days and converted to height inversion errors caused by them. The temporal decorrelations (volume temporal decorrelation) and (ground temporal decorrelation) depend not only on the wind-induced movement but also strongly on the rain-induced dielectric changes in volume and on the ground at temporal baseline on the order of day or longer. At temporal baselines on the order of minutes, the wind speed is a critical parameter and the speed of 2 m/s already hampers the application of Pol-InSAR forest parameter inversion. The approach is supported and validated by using L-band E-SAR repeat-pass data acquired in the frame of three dedicated campaigns, BioSAR 2007, TempoSAR 2008, and TempoSAR 2009.

    @Article{leeKuglerPapathanassiouHajnsekJSTARS2013TempDecorrelationLBand,
    author = {Seung-Kuk Lee and Kugler, Florian and Papathanassiou, Konstantinos P. and Hajnsek, Irena},
    title = {Quantification of Temporal Decorrelation Effects at {L-}Band for Polarimetric SAR Interferometry Applications},
    journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
    year = {2013},
    volume = {6},
    number = {3},
    pages = {1351-1367},
    month = jun,
    issn = {1939-1404},
    abstract = {Temporal decorrelation is the most critical issue for the successful inversion of polarimetric SAR interferometry (Pol-InSAR) data acquired in an interferometric repeat-pass mode, typical for satellite or lower frequency airborne SAR systems. This paper provides a quantitative estimation of temporal decorrelation effects at L-band for a wide range of temporal baselines based on a unique set of multibaseline Pol-InSAR data. A new methodology that allows to quantify individual temporal decorrelation components has been developed and applied. Temporal decorrelation coefficients are estimated for temporal baselines ranging from 10 min to 54 days and converted to height inversion errors caused by them. The temporal decorrelations (volume temporal decorrelation) and (ground temporal decorrelation) depend not only on the wind-induced movement but also strongly on the rain-induced dielectric changes in volume and on the ground at temporal baseline on the order of day or longer. At temporal baselines on the order of minutes, the wind speed is a critical parameter and the speed of 2 m/s already hampers the application of Pol-InSAR forest parameter inversion. The approach is supported and validated by using L-band E-SAR repeat-pass data acquired in the frame of three dedicated campaigns, BioSAR 2007, TempoSAR 2008, and TempoSAR 2009.},
    doi = {10.1109/JSTARS.2013.2253448},
    file = {:leeKuglerPapathanassiouHajnsekJSTARS2013TempDecorrelationLBand.pdf:PDF},
    keywords = {SAR Processing, Decorrelation, Temporal Decorrelation, airborne radar;data acquisition;decorrelation;estimation theory;radar polarimetry;spaceborne radar;synthetic aperture radar;BioSAR 2007;L-band E-SAR repeat-pass data acquisition;Pol-InSAR forest parameter inversion;TempoSAR 2008;TempoSAR 2009;ground temporal decorrelation effect;height inversion error;interferometric repeat-pass mode;multibaseline Pol-InSAR data acquisition;polarimetric SAR interferometry application;quantitative estimation;rain-induced dielectric change;satellite airborne SAR system;temporal baseline estimation;time 10 min to 54 day;velocity 2 m/s;volume temporal decorrelation effect;Height inversion;polarimetric synthetic aperture radar interferometry (Pol-InSAR);temporal baseline;temporal decorrelation},
    pdf = {../../../docs/leeKuglerPapathanassiouHajnsekJSTARS2013TempDecorrelationLBand.pdf},
    
    }
    


  16. Fabrizio Lombardini, Francesco Cai, and Davide Pasculli. Spaceborne 3-D SAR tomography for analyzing garbled urban scenarios: single-look superresolution advances and experiments. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 6(2):960-968, 2013.
    @Article{lombardiniCaiPasculliJSTARS2013TomoUrban,
    author = {Lombardini, Fabrizio and Cai, Francesco and Pasculli, Davide},
    title = {Spaceborne 3-D SAR tomography for analyzing garbled urban scenarios: single-look superresolution advances and experiments},
    year = {2013},
    volume = {6},
    number = {2},
    pages = {960--968},
    journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
    owner = {ofrey},
    publisher = {IEEE},
    
    }
    


  17. R. Magagi, A. A. Berg, K. Goita, S. Belair, T. J. Jackson, B. Toth, A. Walker, H. McNairn, P. E. O'Neill, Mahta Moghaddam, I. Gherboudj, A. Colliander, M. H. Cosh, Mariko S. Burgin, J. B. Fisher, S. B. Kim, I. Mladenova, N. Djamai, L. P. B. Rousseau, J. Belanger, J. Shang, and A. Merzouki. Canadian Experiment for Soil Moisture in 2010 (CanEx-SM10): Overview and Preliminary Results. IEEE Transactions on Geoscience and Remote Sensing, 51(1):347-363, January 2013. Keyword(s): land surface temperature, remote sensing, soil, vegetation, AD 2010, AD 2010 05 31 to 2010 06, AMSR-E soil moisture, CanEx-SM10, Canada, Canadian experiment, National Snow and Ice Data Center, SMOS data, SMOS mission, SMOS soil moisture product, Saskatchewan, active microwave measurement, agricultural area, airborne L-band brightness temperatures, airborne L-band radiometer data, airborne platform, boreal forested area, ocean salinity, passive microwave measurement, radio frequency, reflected soil moisture measurements, satellite platform, soil condition, soil ground-based measurements, soil moisture, soil temperature profiles, vegetation characteristics, vegetation condition, Moisture measurement, Satellites, Soil measurements, Soil moisture, Temperature measurement, Vegetation mapping, Agricultural and boreal forested areas, Soil Moisture and Ocean Salinity (SMOS), brightness temperature, soil moisture, validation.
    Abstract: The Canadian Experiment for Soil Moisture in 2010 (CanEx-SM10) was carried out in Saskatchewan, Canada, from 31 May to 16 June, 2010. Its main objective was to contribute to Soil Moisture and Ocean Salinity (SMOS) mission validation and the prelaunch assessment of the proposed Soil Moisture Active and Passive (SMAP) mission. During CanEx-SM10, SMOS data as well as other passive and active microwave measurements were collected by both airborne and satellite platforms. Ground-based measurements of soil (moisture, temperature, roughness, bulk density) and vegetation characteristics (leaf area index, biomass, vegetation height) were conducted close in time to the airborne and satellite acquisitions. Moreover, two ground-based in situ networks provided continuous measurements of meteorological conditions and soil moisture and soil temperature profiles. Two sites, each covering 33 km x 71 km (about two SMOS pixels) were selected in agricultural and boreal forested areas in order to provide contrasting soil and vegetation conditions. This paper describes the measurement strategy, provides an overview of the data sets, and presents preliminary results. Over the agricultural area, the airborne L-band brightness temperatures matched up well with the SMOS data (prototype 346). The radio frequency interference observed in both SMOS and the airborne L-band radiometer data exhibited spatial and temporal variability and polarization dependency. The temporal evolution of the SMOS soil moisture product (prototype 307) matched that observed with the ground data, but the absolute soil moisture estimates did not meet the accuracy requirements (0.04 m3/m3) of the SMOS mission. AMSR-E soil moisture estimates from the National Snow and Ice Data Center more closely reflected soil moisture measurements.

    @Article{magagiEtAlTGRS2013CanadianSoilMoistureExperiment,
    author = {R. Magagi and A. A. Berg and K. Goita and S. Belair and T. J. Jackson and B. Toth and A. Walker and H. McNairn and P. E. O'Neill and Mahta Moghaddam and I. Gherboudj and A. Colliander and M. H. Cosh and Mariko S. Burgin and J. B. Fisher and S. B. Kim and I. Mladenova and N. Djamai and L. P. B. Rousseau and J. Belanger and J. Shang and A. Merzouki},
    title = {Canadian Experiment for Soil Moisture in 2010 ({CanEx-SM10}): Overview and Preliminary Results},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2013},
    volume = {51},
    number = {1},
    pages = {347-363},
    month = jan,
    issn = {0196-2892},
    abstract = {The Canadian Experiment for Soil Moisture in 2010 (CanEx-SM10) was carried out in Saskatchewan, Canada, from 31 May to 16 June, 2010. Its main objective was to contribute to Soil Moisture and Ocean Salinity (SMOS) mission validation and the prelaunch assessment of the proposed Soil Moisture Active and Passive (SMAP) mission. During CanEx-SM10, SMOS data as well as other passive and active microwave measurements were collected by both airborne and satellite platforms. Ground-based measurements of soil (moisture, temperature, roughness, bulk density) and vegetation characteristics (leaf area index, biomass, vegetation height) were conducted close in time to the airborne and satellite acquisitions. Moreover, two ground-based in situ networks provided continuous measurements of meteorological conditions and soil moisture and soil temperature profiles. Two sites, each covering 33 km x 71 km (about two SMOS pixels) were selected in agricultural and boreal forested areas in order to provide contrasting soil and vegetation conditions. This paper describes the measurement strategy, provides an overview of the data sets, and presents preliminary results. Over the agricultural area, the airborne L-band brightness temperatures matched up well with the SMOS data (prototype 346). The radio frequency interference observed in both SMOS and the airborne L-band radiometer data exhibited spatial and temporal variability and polarization dependency. The temporal evolution of the SMOS soil moisture product (prototype 307) matched that observed with the ground data, but the absolute soil moisture estimates did not meet the accuracy requirements (0.04 m3/m3) of the SMOS mission. AMSR-E soil moisture estimates from the National Snow and Ice Data Center more closely reflected soil moisture measurements.},
    doi = {10.1109/TGRS.2012.2198920},
    file = {:magagiEtAlTGRS2013CanadianSoilMoistureExperiment.pdf:PDF},
    keywords = {land surface temperature;remote sensing;soil;vegetation;AD 2010;AD 2010 05 31 to 2010 06;AMSR-E soil moisture;CanEx-SM10;Canada;Canadian experiment;National Snow and Ice Data Center;SMOS data;SMOS mission;SMOS soil moisture product;Saskatchewan;active microwave measurement;agricultural area;airborne L-band brightness temperatures;airborne L-band radiometer data;airborne platform;boreal forested area;ocean salinity;passive microwave measurement;radio frequency;reflected soil moisture measurements;satellite platform;soil condition;soil ground-based measurements;soil moisture;soil temperature profiles;vegetation characteristics;vegetation condition;Moisture measurement;Satellites;Soil measurements;Soil moisture;Temperature measurement;Vegetation mapping;Agricultural and boreal forested areas;Soil Moisture and Ocean Salinity (SMOS);brightness temperature;soil moisture;validation},
    
    }
    


  18. N. J. Marechal, S. S. Osofsky, and R. M. Bloom. Demonstration of W-band SAR Imagery with a Ground Based System Having 7.5 GHz of Bandwidth Obtained with a Stepped Chirp Waveform. IEEE Transactions on Aerospace and Electronic Systems, 49(4):2522-2532, October 2013. Keyword(s): SAR Processing, W-Band, airborne radar, ground penetrating radar, microwave imaging, millimetre wave imaging, millimetre wave radar, radar antennas, radar detection, radar imaging, radar interferometry, radar resolution, synthetic aperture radar, terrain mapping, airborne high resolution imaging, azimuth resolution, bandwidth 7.5 GHz, data collection, frequency 95 GHz, ground-based security application, ground-based synthetic aperture radar, mapping system, radar antenna, radar detection, repeat pass interferometric SAR, stepped chirp waveform, terrain mapping, w-band SAR imagery, Azimuth, Bandwidth, Image resolution, Radar imaging, Rails, Synthetic aperture radar.
    Abstract: Imagery formed from data collected by a ground-based synthetic aperture radar (SAR) operating at W-band (95 GHz) with a bandwidth of 7.5 GHz is presented. The synthetic aperture is generated by translating the radar antenna along a precision rail mounted atop a two story building which illuminates targets at ground level below. The azimuth resolution achieved is 1.4 cm. The 7.5 GHz of range bandwidth is created as a union of sub-bands using a stepped chirp waveform providing a range resolution of 2.5 cm. Repeat pass interferometric SAR for terrain mapping and change detection are also demonstrated. The results are of particular importance for the development of airborne high resolution imaging and mapping systems, and ground-based security applications.

    @ARTICLE{marechalOsofskyBloomTAES2013WBandSAR,
    author={N. J. Marechal and S. S. Osofsky and R. M. Bloom},
    journal={IEEE Transactions on Aerospace and Electronic Systems},
    title={Demonstration of W-band SAR Imagery with a Ground Based System Having 7.5 GHz of Bandwidth Obtained with a Stepped Chirp Waveform},
    year={2013},
    volume={49},
    number={4},
    pages={2522-2532},
    abstract={Imagery formed from data collected by a ground-based synthetic aperture radar (SAR) operating at W-band (95 GHz) with a bandwidth of 7.5 GHz is presented. The synthetic aperture is generated by translating the radar antenna along a precision rail mounted atop a two story building which illuminates targets at ground level below. The azimuth resolution achieved is 1.4 cm. The 7.5 GHz of range bandwidth is created as a union of sub-bands using a stepped chirp waveform providing a range resolution of 2.5 cm. Repeat pass interferometric SAR for terrain mapping and change detection are also demonstrated. The results are of particular importance for the development of airborne high resolution imaging and mapping systems, and ground-based security applications.},
    keywords={SAR Processing, W-Band, airborne radar;ground penetrating radar;microwave imaging;millimetre wave imaging;millimetre wave radar;radar antennas;radar detection;radar imaging;radar interferometry;radar resolution;synthetic aperture radar;terrain mapping;airborne high resolution imaging;azimuth resolution;bandwidth 7.5 GHz;data collection;frequency 95 GHz;ground-based security application;ground-based synthetic aperture radar;mapping system;radar antenna;radar detection;repeat pass interferometric SAR;stepped chirp waveform;terrain mapping;w-band SAR imagery;Azimuth;Bandwidth;Image resolution;Radar imaging;Rails;Synthetic aperture radar},
    doi={10.1109/TAES.2013.6621833},
    ISSN={0018-9251},
    month=oct,
    owner = {ofrey},
    
    }
    


  19. Mauro Mariotti d' Alessandro, Stefano Tebaldini, and Fabio Rocca. Phenomenology of Ground Scattering in a Tropical Forest Through Polarimetric Synthetic Aperture Radar Tomography. IEEE Trans. Geosci. Remote Sens., 51(8):4430-4437, August 2013. Keyword(s): SAR Processing, Biomass, SAR Tomography, Tomography, Polarimetry, Polarimetric synthetic aperture radar, SAR Interferometry, Interferometry, Multibaseline Interferometry, digital signal processing, forest, longer wavelength radar, P-Band, Airborne SAR, Paracou, French Guyana, ONERA, SETHI, TropiSAR, ESA.
    Abstract: This paper aims at characterizing the scattering mechanisms occurring at the ground level in a tropical forest illuminated by a P-band synthetic aperture radar (SAR). The analysis is carried out based on the multibaseline, fully polarimetric, data set collected by ONERA over Paracou, French Guyana, in the frame of the European space agency campaign TropiSAR. The favorable baseline distribution of this data set results in the possibility of removing most contributions from the vegetation layer by tomographic techniques, thus allowing the generation of a new fully polarimetric single look complex SAR image relative to scattering contributions from the ground level only. Such a ground layer image is then analyzed by considering the variation of its polarimetric signature with respect to terrain local slope and Radar look angle. Two major conclusions are drawn: 1) double bounce scattering from trunk-ground interactions is observed to be the dominant scattering mechanism at the ground level on flat terrains, whereas it rapidly tends to vanish as the topographic slope increases, and 2) the characteristic parameter that rules trunk-ground scattering is not the tree height, but rather the available free path facing the tree, as a result of the presence of nearby trees, undulating topography, or understory preventing double bounce scattering from taking place whenever the ground bounce occurs too far away from the considered tree. The mean free path length resulting from the analysis of this data-set is found to be L approx. 7 m. Finally, we discuss how the concept of free path length can be accounted for in simple terms by assuming an equivalent extinction model characterized by a variation along the horizontal dimension.

    @Article{mariottidAlessandroTebaldiniRoccaTGRS2013,
    author = {Mariotti {d' Alessandro}, Mauro and Tebaldini,Stefano and Rocca,Fabio},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Phenomenology of Ground Scattering in a Tropical Forest Through Polarimetric Synthetic Aperture Radar Tomography},
    year = {2013},
    issn = {0196-2892},
    month = aug,
    number = {8},
    pages = {4430--4437},
    volume = {51},
    abstract = {This paper aims at characterizing the scattering mechanisms occurring at the ground level in a tropical forest illuminated by a P-band synthetic aperture radar (SAR). The analysis is carried out based on the multibaseline, fully polarimetric, data set collected by ONERA over Paracou, French Guyana, in the frame of the European space agency campaign TropiSAR. The favorable baseline distribution of this data set results in the possibility of removing most contributions from the vegetation layer by tomographic techniques, thus allowing the generation of a new fully polarimetric single look complex SAR image relative to scattering contributions from the ground level only. Such a ground layer image is then analyzed by considering the variation of its polarimetric signature with respect to terrain local slope and Radar look angle. Two major conclusions are drawn: 1) double bounce scattering from trunk-ground interactions is observed to be the dominant scattering mechanism at the ground level on flat terrains, whereas it rapidly tends to vanish as the topographic slope increases, and 2) the characteristic parameter that rules trunk-ground scattering is not the tree height, but rather the available free path facing the tree, as a result of the presence of nearby trees, undulating topography, or understory preventing double bounce scattering from taking place whenever the ground bounce occurs too far away from the considered tree. The mean free path length resulting from the analysis of this data-set is found to be L approx. 7 m. Finally, we discuss how the concept of free path length can be accounted for in simple terms by assuming an equivalent extinction model characterized by a variation along the horizontal dimension.},
    doi = {10.1109/TGRS.2013.2246573},
    file = {:mariottidAlessandroTebaldiniRoccaTGRS2013.pdf:PDF},
    keywords = {SAR Processing, Biomass, SAR Tomography, Tomography, Polarimetry, Polarimetric synthetic aperture radar, SAR Interferometry, Interferometry, Multibaseline Interferometry, digital signal processing;forest;longer wavelength radar, P-Band, Airborne SAR, Paracou, French Guyana, ONERA, SETHI,TropiSAR, ESA},
    pdf = {../../../docs/mariottidAlessandroTebaldiniRoccaTGRS2013.pdf},
    publisher = {Institute of Electrical and Electronics Engineers ({IEEE})},
    
    }
    


  20. Kyra Moon and David G. Long. A New Factorized Backprojection Algorithm for Stripmap Synthetic Aperture Radar. Positioning, 4:42-56, 2013. Keyword(s): SAR Processing, Azimuth Focusing, Time-domain back-projection, TDBP, SAR focusing, motion compensation, radar signal processing, synthetic aperture radar, 3D motion compensation, SAR processing scheme, agile SAR platforms, time domain backprojection processing, Fast-Factorized Back-Projection, FFBP, Fast Back-Projection, Synthetic aperture radar.
    Abstract: Factorized backprojection is a processing algorithm for reconstructing images from data collected by synthetic aperture radar (SAR) systems. Factorized backprojection requires less computation than conventional time-domain backprojection with minimal loss in accuracy for straight-line motion. However, its implementation is not as straightforward as direct backprojection. This paper provides a new, easily parallelizable formulation of factorized backprojection designed for stripmap SAR data that includes a method of implementing an azimuth window as part of the factorized backprojection algorithm. We compare the performance of windowed factorized backprojection to direct backprojection for simulated and actual SAR data.

    @Article{moonLongPositioning201FFBP,
    author = {Moon, Kyra and Long, David G.},
    title = {A New Factorized Backprojection Algorithm for Stripmap Synthetic Aperture Radar},
    journal = {Positioning},
    year = {2013},
    volume = {4},
    pages = {42-56},
    abstract = {Factorized backprojection is a processing algorithm for reconstructing images from data collected by synthetic aperture radar (SAR) systems. Factorized backprojection requires less computation than conventional time-domain backprojection with minimal loss in accuracy for straight-line motion. However, its implementation is not as straightforward as direct backprojection. This paper provides a new, easily parallelizable formulation of factorized backprojection designed for stripmap SAR data that includes a method of implementing an azimuth window as part of the factorized backprojection algorithm. We compare the performance of windowed factorized backprojection to direct backprojection for simulated and actual SAR data.},
    doi = {10.4236/pos.2013.41006},
    file = {:moonLongPositioning201FFBP.pdf:PDF},
    keywords = {SAR Processing, Azimuth Focusing, Time-domain back-projection, TDBP, SAR focusing, motion compensation; radar signal processing;synthetic aperture radar; 3D motion compensation; SAR processing scheme;agile SAR platforms; time domain backprojection processing; Fast-Factorized Back-Projection, FFBP, Fast Back-Projection, Synthetic aperture radar},
    pdf = {../../../docs/moonLongPositioning201FFBP.pdf},
    
    }
    


  21. Alberto Moreira, Pau Prats-Iraola, Marwan Younis, Gerhard Krieger, Irena Hajnsek, and Konstantinos P. Papathanassiou. A tutorial on synthetic aperture radar. IEEE Geoscience and Remote Sensing Magazine, 1(1):6-43, March 2013. Keyword(s): SAR Processing, Tutorial, SAR Focusing, Azimuth Focusing, SAR Interferometry, SAR Polarimetry, polarimetric interferometry, PolInSAR, InSAR, SAR Tomography, geophysical techniques, radar interferometry, radar polarimetry, remote sensing by radar, synthetic aperture radar, Earth remote sensing, bistatic configurations, differential interferometry, digital beamforming, holographic tomography, multiple-input multiple-output, multistatic configurations, polarimetric SAR interferometry, polarimetry, synthetic aperture radar, Radar imaging, Remote sensing, Scattering, Spaceborne radar, Synthetic aperture radar, Tutorial, Teaching Material.
    Abstract: Synthetic Aperture Radar (SAR) has been widely used for Earth remote sensing for more than 30 years. It provides high-resolution, day-and-night and weather-independent images for a multitude of applications ranging from geoscience and climate change research, environmental and Earth system monitoring, 2-D and 3-D mapping, change detection, 4-D mapping (space and time), security-related applications up to planetary exploration. With the advances in radar technology and geo/bio-physical parameter inversion modeling in the 90s, using data from several airborne and spaceborne systems, a paradigm shift occurred from the development driven by the technology push to the user demand pull. Today, more than 15 spaceborne SAR systems are being operated for innumerous applications. This paper provides first a tutorial about the SAR principles and theory, followed by an overview of established techniques like polarimetry, interferometry and differential interferometry as well as of emerging techniques (e.g., polarimetric SAR interferometry, tomography and holographic tomography). Several application examples including the associated parameter inversion modeling are provided for each case. The paper also describes innovative technologies and concepts like digital beamforming, Multiple-Input Multiple-Output (MIMO) and bi- and multi-static configurations which are suitable means to fulfill the increasing user requirements. The paper concludes with a vision for SAR remote sensing.

    @Article{moreiraPratsYounisKriegerHajnsekPapathanassiouGRSMagazine2013,
    author = {Moreira, Alberto and Prats-Iraola, Pau and Younis, Marwan and Krieger, Gerhard and Hajnsek, Irena and Papathanassiou, Konstantinos P.},
    title = {A tutorial on synthetic aperture radar},
    journal = {IEEE Geoscience and Remote Sensing Magazine},
    year = {2013},
    volume = {1},
    number = {1},
    pages = {6-43},
    month = mar,
    issn = {2168-6831},
    abstract = {Synthetic Aperture Radar (SAR) has been widely used for Earth remote sensing for more than 30 years. It provides high-resolution, day-and-night and weather-independent images for a multitude of applications ranging from geoscience and climate change research, environmental and Earth system monitoring, 2-D and 3-D mapping, change detection, 4-D mapping (space and time), security-related applications up to planetary exploration. With the advances in radar technology and geo/bio-physical parameter inversion modeling in the 90s, using data from several airborne and spaceborne systems, a paradigm shift occurred from the development driven by the technology push to the user demand pull. Today, more than 15 spaceborne SAR systems are being operated for innumerous applications. This paper provides first a tutorial about the SAR principles and theory, followed by an overview of established techniques like polarimetry, interferometry and differential interferometry as well as of emerging techniques (e.g., polarimetric SAR interferometry, tomography and holographic tomography). Several application examples including the associated parameter inversion modeling are provided for each case. The paper also describes innovative technologies and concepts like digital beamforming, Multiple-Input Multiple-Output (MIMO) and bi- and multi-static configurations which are suitable means to fulfill the increasing user requirements. The paper concludes with a vision for SAR remote sensing.},
    doi = {10.1109/MGRS.2013.2248301},
    file = {:moreiraPratsYounisKriegerHajnsekPapathanassiouGRSMagazine2013.pdf:PDF},
    keywords = {SAR Processing, Tutorial, SAR Focusing, Azimuth Focusing, SAR Interferometry, SAR Polarimetry, polarimetric interferometry, PolInSAR, InSAR, SAR Tomography, geophysical techniques;radar interferometry;radar polarimetry;remote sensing by radar;synthetic aperture radar;Earth remote sensing;bistatic configurations;differential interferometry;digital beamforming;holographic tomography;multiple-input multiple-output;multistatic configurations;polarimetric SAR interferometry;polarimetry;synthetic aperture radar;Radar imaging;Remote sensing;Scattering;Spaceborne radar;Synthetic aperture radar;Tutorial, Teaching Material},
    pdf = {../../../docs/moreiraPratsYounisKriegerHajnsekPapathanassiouGRSMagazine2013.pdf},
    
    }
    


  22. K. Morrison, J. C. Bennett, and M. Nolan. Using DInSAR to Separate Surface and Subsurface Features. IEEE_J_GRS, 51(6):3424-3430, June 2013. Keyword(s): radar imaging, radar interferometry, soil, synthetic aperture radar, C-band VV SAR images, DInSAR scheme, Ground-Based SAR Microwave Measurement Facility, SAR DInSAR, airborne platform, differential interferometric synthetic aperture radar, drying soil, moisture content, phase soil moisture, signal phase record, soil dielectric properties, spaceborne platform, volumetric soil moisture, Radar imaging, Soil measurements, Soil moisture, Spaceborne radar, Synthetic aperture radar, Dielectric materials, ground-penetrating radar, moisture measurement, permittivity measurement, radar imaging, radar signal analysis, radar signature, soil measurements, synthetic aperture imaging, synthetic aperture radar (SAR).
    @Article{Morrison2013,
    author = {K. Morrison and J. C. Bennett and M. Nolan},
    title = {Using DInSAR to Separate Surface and Subsurface Features},
    year = {2013},
    volume = {51},
    number = {6},
    month = jun,
    pages = {3424--3430},
    issn = {0196-2892},
    doi = {10.1109/TGRS.2012.2226183},
    journal = IEEE_J_GRS,
    keywords = {radar imaging, radar interferometry, soil, synthetic aperture radar, C-band VV SAR images, DInSAR scheme, Ground-Based SAR Microwave Measurement Facility, SAR DInSAR, airborne platform, differential interferometric synthetic aperture radar, drying soil, moisture content, phase soil moisture, signal phase record, soil dielectric properties, spaceborne platform, volumetric soil moisture, Radar imaging, Soil measurements, Soil moisture, Spaceborne radar, Synthetic aperture radar, Dielectric materials, ground-penetrating radar, moisture measurement, permittivity measurement, radar imaging, radar signal analysis, radar signature, soil measurements, synthetic aperture imaging, synthetic aperture radar (SAR)},
    owner = {ofrey},
    
    }
    


  23. S. Perna, V. Zamparelli, A. Pauciullo, and G. Fornaro. Azimuth-to-Frequency Mapping in Airborne SAR Data Corrupted by Uncompensated Motion Errors. Geoscience and Remote Sensing Letters, IEEE, 10(6):1493-1497, November 2013. Keyword(s): remote sensing by radar, synthetic aperture radar, MOCO algorithm, airborne SAR raw data, azimuth-to-frequency mapping, precise aperture-dependent procedure, precise topography-dependent procedure, standard two-step motion compensation, synthetic aperture radar, uncompensated motion errors, Airborne SAR, SAR motion compensation, synthetic aperture radar (SAR).
    Abstract: Airborne synthetic aperture radar (SAR) raw data are affected by motion errors. These are commonly accounted for via standard two-step motion compensation (MOCO) algorithm followed by the Precise Topography- and Aperture-dependent (PTA) procedure proposed some years ago. In this letter, we show how the azimuth-to-frequency mapping used by the PTA approach should be modified to fully account for the presence of uncompensated motion errors.

    @Article{pernaZamparelliPauciulloFornaroGRSL2013,
    author = {Perna, S. and Zamparelli, V. and Pauciullo, A. and Fornaro, G.},
    title = {Azimuth-to-Frequency Mapping in Airborne SAR Data Corrupted by Uncompensated Motion Errors},
    journal = {Geoscience and Remote Sensing Letters, IEEE},
    year = {2013},
    volume = {10},
    number = {6},
    pages = {1493-1497},
    month = {Nov},
    issn = {1545-598X},
    abstract = {Airborne synthetic aperture radar (SAR) raw data are affected by motion errors. These are commonly accounted for via standard two-step motion compensation (MOCO) algorithm followed by the Precise Topography- and Aperture-dependent (PTA) procedure proposed some years ago. In this letter, we show how the azimuth-to-frequency mapping used by the PTA approach should be modified to fully account for the presence of uncompensated motion errors.},
    doi = {10.1109/LGRS.2013.2260721},
    file = {:pernaZamparelliPauciulloFornaroGRSL2013.pdf:PDF},
    keywords = {remote sensing by radar;synthetic aperture radar;MOCO algorithm;airborne SAR raw data;azimuth-to-frequency mapping;precise aperture-dependent procedure;precise topography-dependent procedure;standard two-step motion compensation;synthetic aperture radar;uncompensated motion errors;Airborne SAR;SAR motion compensation;synthetic aperture radar (SAR)},
    pdf = {../../../docs/pernaZamparelliPauciulloFornaroGRSL2013.pdf},
    
    }
    


  24. Luca Pipia, Xavier Fabregas, Albert Aguasca, and Carlos Lopez-Martinez. Polarimetric Temporal Analysis of Urban Environments With a Ground-Based SAR. IEEE Trans. Geosci. Remote Sens., 51(4):2343-2360, 2013. Keyword(s): SAR Processing, Ground-based SAR, GBSAR, DInSAR, Differential SAR Interferometry, X-Band, Time series, Polarimetry, SAR Polarimetry, Backscatter, Geologic measurements, Monitoring, Scattering, Stability analysis, Synthetic aperture radar, Urban areas, Ground-based synthetic aperture radar (gbSAR) systems, polarimetric entropy, radar polarimetry.
    Abstract: Revisiting time constitutes a key constraint for continuous monitoring activities based on space- and airborne synthetic aperture radar (SAR) acquisitions. Conversely, the employment of terrestrial platforms overcomes this limitation and makes it possible to perform time-continuous observations of small space-scale phenomena. New research lines of SAR dealing with the backscattering evolution of different types of scenarios become hence possible through the analysis of ground-based SAR (gbSAR) data collections. The Remote Sensing Laboratory of the Universitat Politecnica de Catalunya drove a one-year measurements campaign in the village of Sallent, northeastern Spain, using its X-Band gbSAR sensor. The field experiment aimed at studying the subsidence phenomenon induced by the salt mining activity carried out in this area during the past decades. In this paper, the polarimetric behavior of an urban environment is investigated at different time scales. After a brief description of the test site and the measurement campaign, the analysis is focused on the stability on man-made structures at different time scales. PolSAR data monthly acquired from June 2006 to July 2007 are employed to stress the presence of nonstationary backscattering processes within the urban scene and the effect they have on differential phase information. Then, a filtering procedure aiming at reducing backscattering randomness in one-day and long-term data collections is then put forward. The improvements provided by the proposed technique are assessed using a new polarimetric descriptor, the time entropy. In the end, the importance of preserving the interferometric phase information from nonstationary backscattering contaminations using fully polarimetric data is discussed.

    @Article{pipiaFabregasAquascaLopezMartinez2013GBSAR,
    Title = {Polarimetric Temporal Analysis of Urban Environments With a Ground-Based {SAR}},
    Author = {Pipia, Luca and Fabregas, Xavier and Aguasca, Albert and Lopez-Martinez, Carlos},
    Doi = {10.1109/TGRS.2012.2211369},
    ISSN = {0196-2892},
    Number = {4},
    Pages = {2343-2360},
    Volume = {51},
    Year = {2013},
    Abstract = {Revisiting time constitutes a key constraint for continuous monitoring activities based on space- and airborne synthetic aperture radar (SAR) acquisitions. Conversely, the employment of terrestrial platforms overcomes this limitation and makes it possible to perform time-continuous observations of small space-scale phenomena. New research lines of SAR dealing with the backscattering evolution of different types of scenarios become hence possible through the analysis of ground-based SAR (gbSAR) data collections. The Remote Sensing Laboratory of the Universitat Politecnica de Catalunya drove a one-year measurements campaign in the village of Sallent, northeastern Spain, using its X-Band gbSAR sensor. The field experiment aimed at studying the subsidence phenomenon induced by the salt mining activity carried out in this area during the past decades. In this paper, the polarimetric behavior of an urban environment is investigated at different time scales. After a brief description of the test site and the measurement campaign, the analysis is focused on the stability on man-made structures at different time scales. PolSAR data monthly acquired from June 2006 to July 2007 are employed to stress the presence of nonstationary backscattering processes within the urban scene and the effect they have on differential phase information. Then, a filtering procedure aiming at reducing backscattering randomness in one-day and long-term data collections is then put forward. The improvements provided by the proposed technique are assessed using a new polarimetric descriptor, the time entropy. In the end, the importance of preserving the interferometric phase information from nonstationary backscattering contaminations using fully polarimetric data is discussed.},
    Journal = {IEEE Trans. Geosci. Remote Sens.},
    Keywords = {SAR Processing, Ground-based SAR, GBSAR, DInSAR, Differential SAR Interferometry, X-Band, Time series, Polarimetry, SAR Polarimetry, Backscatter;Geologic measurements;Monitoring;Scattering;Stability analysis;Synthetic aperture radar;Urban areas;Ground-based synthetic aperture radar (gbSAR) systems;polarimetric entropy;radar polarimetry},
    Pdf = {../../../docs/pipiaFabregasAquascaLopezMartinez2013GBSAR.pdf} 
    }
    


  25. F. Prieur and Roy E. Hansen. Theoretical Improvements When Using the Second Harmonic Signal in Acoustic Doppler Current Profilers. IEEE Journal of Oceanic Engineering, 38(2):275-284, April 2013. Keyword(s): Synthetic Aperture Sonar, SAS, Doppler shift, acoustic pulses, acoustic signal processing, acoustic wave velocity, autonomous underwater vehicles, harmonic generation, signal generators, underwater sound, Doppler frequency shift, Doppler log transmission, acoustic Doppler current profilers, floating particles, frequency 153.6 kHz, geometrical properties, geometry, harmonic signal generation, mainlobe-to-sidelobe ratio, perturbations, power 250 W, pulse transmission, sea bottom, second harmonic signal, size 400 m, velocity estimation error, velocity logs, vessel relative, water currents, Acoustic beams, Doppler shift, Estimation, Harmonic analysis, Transducers, Vectors, Current profiler, Doppler, harmonic, nonlinearity.
    Abstract: Acoustic Doppler current profilers and velocity logs are devices that compute the Doppler frequency shift undergone by a pulse after reflection by floating particles in water or by the seafloor. Using this Doppler shift, the velocity of the water currents carrying the reflecting particles or the speed of a vessel relative to the sea bottom can be estimated. The attainable performance of Doppler logs in terms of range and velocity estimate error are directly linked to the physical dimensions and geometry of the transceivers as well as the nature of the pulse transmitted. Beyond a certain transmitted power, distortion of the transmitted pulse due to nonlinear effects is significant. The second harmonic signal generated in that case can be used to estimate velocity in conjunction with the fundamental signal. It has a narrower mainlobe and a higher mainlobe-to-sidelobe ratio compared to the fundamental signal. Such geometrical properties contribute to a more localized velocity determination with less perturbations coming from scatterers away from the region of interest. Combining the velocity estimates using the fundamental and second harmonic signals also helps decreasing the velocity estimate error. For a Doppler log transmitting a pulse at 153.6 kHz using 250-W input power with a nominal range of 400 m, the attainable range for the second harmonic signal is estimated to around 221 m.

    @Article{prieurHansenJOE2013SASImprovementsUsingSecondHarmonicInAcousticDopplerCurrentProfilers,
    author = {F. Prieur and Hansen, Roy E.},
    title = {Theoretical Improvements When Using the Second Harmonic Signal in Acoustic {D}oppler Current Profilers},
    journal = {IEEE Journal of Oceanic Engineering},
    year = {2013},
    volume = {38},
    number = {2},
    pages = {275-284},
    month = {April},
    issn = {0364-9059},
    abstract = {Acoustic Doppler current profilers and velocity logs are devices that compute the Doppler frequency shift undergone by a pulse after reflection by floating particles in water or by the seafloor. Using this Doppler shift, the velocity of the water currents carrying the reflecting particles or the speed of a vessel relative to the sea bottom can be estimated. The attainable performance of Doppler logs in terms of range and velocity estimate error are directly linked to the physical dimensions and geometry of the transceivers as well as the nature of the pulse transmitted. Beyond a certain transmitted power, distortion of the transmitted pulse due to nonlinear effects is significant. The second harmonic signal generated in that case can be used to estimate velocity in conjunction with the fundamental signal. It has a narrower mainlobe and a higher mainlobe-to-sidelobe ratio compared to the fundamental signal. Such geometrical properties contribute to a more localized velocity determination with less perturbations coming from scatterers away from the region of interest. Combining the velocity estimates using the fundamental and second harmonic signals also helps decreasing the velocity estimate error. For a Doppler log transmitting a pulse at 153.6 kHz using 250-W input power with a nominal range of 400 m, the attainable range for the second harmonic signal is estimated to around 221 m.},
    doi = {10.1109/JOE.2012.2226520},
    file = {:prieurHansenJOE2013SASImprovementsUsingSecondHarmonicInAcousticDopplerCurrentProfilers.pdf:PDF},
    keywords = {Synthetic Aperture Sonar, SAS,Doppler shift;acoustic pulses;acoustic signal processing;acoustic wave velocity;autonomous underwater vehicles;harmonic generation;signal generators;underwater sound;Doppler frequency shift;Doppler log transmission;acoustic Doppler current profilers;floating particles;frequency 153.6 kHz;geometrical properties;geometry;harmonic signal generation;mainlobe-to-sidelobe ratio;perturbations;power 250 W;pulse transmission;sea bottom;second harmonic signal;size 400 m;velocity estimation error;velocity logs;vessel relative;water currents;Acoustic beams;Doppler shift;Estimation;Harmonic analysis;Transducers;Vectors;Current profiler;Doppler;harmonic;nonlinearity},
    
    }
    


  26. Diego Reale, Gianfranco Fornaro, and Antonio Pauciullo. Extension of 4-D SAR imaging to the monitoring of thermally dilating scatterers. IEEE Transactions on Geoscience and Remote Sensing, 51(12):5296-5306, 2013.
    @Article{realeFornaroPauciulloTGRS2013Tomo4DThermal,
    author = {Reale, Diego and Fornaro, Gianfranco and Pauciullo, Antonio},
    title = {Extension of {4-D} {SAR} imaging to the monitoring of thermally dilating scatterers},
    year = {2013},
    volume = {51},
    number = {12},
    pages = {5296--5306},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    owner = {ofrey},
    publisher = {IEEE},
    
    }
    


  27. Andreas Reigber, Rolf Scheiber, Marc Jäger, Pau Prats-Iraola, Irena Hajnsek, Thomas Jagdhuber, Konstantinos P. Papathanassiou, Matteo Nannini, Esteban Aguilera, S. Baumgartner, Ralf Horn, Anton Nottensteiner, and Alberto Moreira. Very-High-Resolution Airborne Synthetic Aperture Radar Imaging: Signal Processing and Applications. Proceedings of the IEEE, 101(3):759-783, March 2013. Keyword(s): Applications, high resolution, signal processing, synthetic aperture radar (SAR);.
    Abstract: During the last decade, synthetic aperture radar (SAR) became an indispensable source of information in Earth observation. This has been possible mainly due to the current trend toward higher spatial resolution and novel imaging modes. A major driver for this development has been and still is the airborne SAR technology, which is usually ahead of the capabilities of spaceborne sensors by several years. Today's airborne sensors are capable of delivering high-quality SAR data with decimeter resolution and allow the development of novel approaches in data analysis and information extraction from SAR. In this paper, a review about the abilities and needs of today's very high-resolution airborne SAR sensors is given, based on and summarizing the longtime experience of the German Aerospace Center (DLR) with airborne SAR technology and its applications. A description of the specific requirements of high-resolution airborne data processing is presented, followed by an extensive overview of emerging applications of high-resolution SAR. In many cases, information extraction from high-resolution airborne SAR imagery has achieved a mature level, turning SAR technology more and more into an operational tool. Such abilities, which are today mostly limited to airborne SAR, might become typical in the next generation of spaceborne SAR missions.

    @Article{reigberEtAlProcIEEE2012,
    author = {Reigber, Andreas and Scheiber, Rolf and J{\"a}ger, Marc and Prats-Iraola, Pau and Hajnsek, Irena and Jagdhuber, Thomas and Papathanassiou, Konstantinos P. and Nannini, Matteo and Aguilera, Esteban and Baumgartner, S. and Horn, Ralf and Nottensteiner, Anton and Moreira, Alberto},
    title = {Very-High-Resolution Airborne Synthetic Aperture Radar Imaging: Signal Processing and Applications},
    journal = {Proceedings of the IEEE},
    year = {2013},
    volume = {101},
    number = {3},
    pages = {759-783},
    month = mar,
    issn = {0018-9219},
    abstract = {During the last decade, synthetic aperture radar (SAR) became an indispensable source of information in Earth observation. This has been possible mainly due to the current trend toward higher spatial resolution and novel imaging modes. A major driver for this development has been and still is the airborne SAR technology, which is usually ahead of the capabilities of spaceborne sensors by several years. Today's airborne sensors are capable of delivering high-quality SAR data with decimeter resolution and allow the development of novel approaches in data analysis and information extraction from SAR. In this paper, a review about the abilities and needs of today's very high-resolution airborne SAR sensors is given, based on and summarizing the longtime experience of the German Aerospace Center (DLR) with airborne SAR technology and its applications. A description of the specific requirements of high-resolution airborne data processing is presented, followed by an extensive overview of emerging applications of high-resolution SAR. In many cases, information extraction from high-resolution airborne SAR imagery has achieved a mature level, turning SAR technology more and more into an operational tool. Such abilities, which are today mostly limited to airborne SAR, might become typical in the next generation of spaceborne SAR missions.},
    doi = {10.1109/JPROC.2012.2220511},
    file = {:reigberEtAlProcIEEE2012.pdf:PDF},
    keywords = {Applications;high resolution;signal processing;synthetic aperture radar (SAR);},
    pdf = {../../../docs/reigberEtAlProcIEEE2012.pdf},
    
    }
    


  28. Maxwell L Rudolph, Manoochehr Shirzaei, M Manga, and Y Fukushima. Evolution and future of the Lusi mud eruption inferred from ground deformation. Geophysical Research Letters, 40(6):1089-1092, 2013.
    @Article{Rudolph2013,
    author = {Rudolph, Maxwell L and Shirzaei, Manoochehr and Manga, M and Fukushima, Y},
    title = {Evolution and future of the Lusi mud eruption inferred from ground deformation},
    year = {2013},
    volume = {40},
    number = {6},
    pages = {1089--1092},
    journal = {Geophysical Research Letters},
    owner = {ofrey},
    publisher = {Wiley Online Library},
    
    }
    


  29. T. O. Saebo, S. A. V. Synnes, and Roy E. Hansen. Wideband Interferometry in Synthetic Aperture Sonar. IEEE Transactions on Geoscience and Remote Sensing, 51(8):4450-4459, August 2013. Keyword(s): Synthetic Aperture Sonar, SAS, autonomous aerial vehicles, geophysical image processing, image resolution, oceanographic equipment, oceanographic techniques, radar imaging, radar interferometry, remote sensing by radar, synthetic aperture radar, Goldstein branch cut phase unwrapping algorithm, HISAS wideband interferometric SAS, HUGIN autonomous underwater vehicle, SAS interferometry, absolute phase difference, advanced phase unwrapping techniques, complex cross correlation technique, direct phase difference estimation, final phase estimate, high resolution images, interferometric data processing, misregistrated areas, multiband split spectrum technique, multichromatic approach, narrowband interferometry processing, phase ambiguities, seafloor, synthetic aperture sonar interferometry, topographic maps, wideband interferometry techniques, Delay effects, Interferometry, Maximum likelihood estimation, Synthetic aperture sonar, Wideband, Complex cross correlation, multichromatic analysis, split spectrum algorithm, synthetic aperture radar (SAR), synthetic aperture sonar (SAS), wideband interferometry.
    Abstract: Synthetic aperture sonar (SAS) interferometry can provide very high resolution images and topographic maps of the seafloor over large swaths. Processing of interferometric data to retrieve reliable depth estimates of the seafloor is, however, nontrivial. Traditional narrowband interferometry processing relies on advanced phase unwrapping techniques, constraints, and prior knowledge to resolve phase ambiguities. These methods all have dependencies throughout the dataset, e.g., a small error in the assumption may cause a global error in the final phase estimate. For wideband systems, there are alternative techniques to estimate the absolute (or ambiguity-free) phase difference directly. We consider four different wideband interferometry techniques for direct phase difference estimation: complex cross correlation, split-spectrum algorithm, and the multichromatic approach. In addition, we develop a weighted split-spectrum algorithm, where the weights minimize the variance in the absolute phase estimate. We benchmark these techniques on simulated data and demonstrate the techniques on real data from the HISAS wideband interferometric SAS on a HUGIN autonomous underwater vehicle. We have found the following: the cross correlation technique always outperforms the other techniques in misregistrated areas caused by severe topographic changes. The split spectrum techniques are substantially faster than the cross correlation technique. The multichromatic approach has similar performance as the multiband split spectrum technique for the same choice of bands. We demonstrate that all the wideband interferometry techniques outperform a standard Goldstein's Branch cut phase unwrapping algorithm on real data from a complicated scene containing an elevated target and severe layover.

    @Article{saeboSynnesHansenTGRS2013WidebandInterferometryInSyntheticApertureSonar,
    author = {T. O. Saebo and S. A. V. Synnes and Roy E. Hansen},
    title = {Wideband Interferometry in Synthetic Aperture Sonar},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2013},
    volume = {51},
    number = {8},
    pages = {4450-4459},
    month = aug,
    issn = {0196-2892},
    abstract = {Synthetic aperture sonar (SAS) interferometry can provide very high resolution images and topographic maps of the seafloor over large swaths. Processing of interferometric data to retrieve reliable depth estimates of the seafloor is, however, nontrivial. Traditional narrowband interferometry processing relies on advanced phase unwrapping techniques, constraints, and prior knowledge to resolve phase ambiguities. These methods all have dependencies throughout the dataset, e.g., a small error in the assumption may cause a global error in the final phase estimate. For wideband systems, there are alternative techniques to estimate the absolute (or ambiguity-free) phase difference directly. We consider four different wideband interferometry techniques for direct phase difference estimation: complex cross correlation, split-spectrum algorithm, and the multichromatic approach. In addition, we develop a weighted split-spectrum algorithm, where the weights minimize the variance in the absolute phase estimate. We benchmark these techniques on simulated data and demonstrate the techniques on real data from the HISAS wideband interferometric SAS on a HUGIN autonomous underwater vehicle. We have found the following: the cross correlation technique always outperforms the other techniques in misregistrated areas caused by severe topographic changes. The split spectrum techniques are substantially faster than the cross correlation technique. The multichromatic approach has similar performance as the multiband split spectrum technique for the same choice of bands. We demonstrate that all the wideband interferometry techniques outperform a standard Goldstein's Branch cut phase unwrapping algorithm on real data from a complicated scene containing an elevated target and severe layover.},
    doi = {10.1109/TGRS.2013.2244900},
    file = {:saeboSynnesHansenTGRS2013WidebandInterferometryInSyntheticApertureSonar.pdf:PDF},
    keywords = {Synthetic Aperture Sonar, SAS,autonomous aerial vehicles;geophysical image processing;image resolution;oceanographic equipment;oceanographic techniques;radar imaging;radar interferometry;remote sensing by radar;synthetic aperture radar;Goldstein branch cut phase unwrapping algorithm;HISAS wideband interferometric SAS;HUGIN autonomous underwater vehicle;SAS interferometry;absolute phase difference;advanced phase unwrapping techniques;complex cross correlation technique;direct phase difference estimation;final phase estimate;high resolution images;interferometric data processing;misregistrated areas;multiband split spectrum technique;multichromatic approach;narrowband interferometry processing;phase ambiguities;seafloor;synthetic aperture sonar interferometry;topographic maps;wideband interferometry techniques;Delay effects;Interferometry;Maximum likelihood estimation;Synthetic aperture sonar;Wideband;Complex cross correlation;multichromatic analysis;split spectrum algorithm;synthetic aperture radar (SAR);synthetic aperture sonar (SAS);wideband interferometry},
    
    }
    


  30. Manoochehr Shirzaei. A wavelet-based multitemporal DInSAR algorithm for monitoring ground surface motion. IEEE Geoscience and Remote Sensing Letters, 10(3):456-460, 2013.
    @Article{Shirzaei2013a,
    author = {Shirzaei, Manoochehr},
    title = {A wavelet-based multitemporal DInSAR algorithm for monitoring ground surface motion},
    year = {2013},
    volume = {10},
    number = {3},
    pages = {456--460},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    owner = {ofrey},
    publisher = {IEEE},
    
    }
    


  31. Manoochehr Shirzaei and Roland Bürgmann. Time-dependent model of creep on the Hayward fault from joint inversion of 18 years of InSAR and surface creep data. Journal of Geophysical Research: Solid Earth, 118(4):1733-1746, 2013.
    @Article{Shirzaei2013,
    author = {Shirzaei, Manoochehr and B{\"u}rgmann, Roland},
    title = {Time-dependent model of creep on the Hayward fault from joint inversion of 18 years of InSAR and surface creep data},
    year = {2013},
    volume = {118},
    number = {4},
    pages = {1733--1746},
    journal = {Journal of Geophysical Research: Solid Earth},
    owner = {ofrey},
    publisher = {Wiley Online Library},
    
    }
    


  32. Manoochehr Shirzaei, R Bürgmann, J Foster, TR Walter, and BA Brooks. Aseismic deformation across the Hilina fault system, Hawaii, revealed by wavelet analysis of InSAR and GPS time series. Earth and Planetary Science Letters, 376:12-19, 2013.
    @Article{Shirzaei2013b,
    author = {Shirzaei, Manoochehr and B{\"u}rgmann, R and Foster, J and Walter, TR and Brooks, BA},
    title = {Aseismic deformation across the Hilina fault system, Hawaii, revealed by wavelet analysis of InSAR and GPS time series},
    year = {2013},
    volume = {376},
    pages = {12--19},
    journal = {Earth and Planetary Science Letters},
    owner = {ofrey},
    publisher = {Elsevier},
    
    }
    


  33. Manoochehr Shirzaei, Thomas R Walter, and Roland Bürgmann. Coupling of Hawaiian volcanoes only during overpressure condition. Geophysical Research Letters, 40(10):1994-1999, 2013.
    @Article{Shirzaei2013d,
    author = {Shirzaei, Manoochehr and Walter, Thomas R and B{\"u}rgmann, Roland},
    title = {Coupling of Hawaiian volcanoes only during overpressure condition},
    year = {2013},
    volume = {40},
    number = {10},
    pages = {1994--1999},
    journal = {Geophysical Research Letters},
    owner = {ofrey},
    publisher = {Wiley Online Library},
    
    }
    


  34. Luigi Tosi, Pietro Teatini, and Tazio Strozzi. Natural versus anthropogenic subsidence of Venice. Scientific Reports, 3:2710-, September 2013.
    @Article{tosiTeatiniStrozziScientificRepNature2013SubsidenceVenice,
    author = {Tosi, Luigi and Teatini, Pietro and Strozzi, Tazio},
    title = {Natural versus anthropogenic subsidence of {Venice}},
    journal = {Scientific Reports},
    year = {2013},
    volume = {3},
    pages = {2710--},
    month = sep,
    file = {:tosiTeatiniStrozziScientificRepNature2013SubsidenceVenice.pdf:PDF},
    owner = {ofrey},
    pdf = {../../../docs/tosiTeatiniStrozziScientificRepNature2013SubsidenceVenice.pdf},
    url = {http://dx.doi.org/10.1038/srep02710},
    
    }
    


  35. Viet Thuy Vu, Thomas K. Sjogren, and Mats I. Pettersson. Fast Time-Domain Algorithms for UWB Bistatic SAR Processing. IEEE Trans. Aerosp. Electron. Syst., 49(3):1982-1994, July 2013. Keyword(s): SAR Processing, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, Bistatic SAR, Bistatic Fast-Factorized Back-Projection, BiFFBP, radar cross-sections, radar imaging, synthetic aperture radar, time-domain analysis, ultra wideband radar, BiFFBP, CARABAS-II, UWB bistatic SAR, bistatic fast factorized backprojection, radar echo, radar signal processing, subaperture, subimage basis, synthetic aperture radar, time-domain algorithm, ultra wideband radar, ultra widebeam radar, Radar imaging, Receivers, Signal processing algorithms, Synthetic aperture radar, Time-domain analysis, Transmitters.
    Abstract: Two fast time-domain algorithms are introduced for ultrawideband-ultrawidebeam (UWB) bistatic synthetic aperture radar (SAR) processing; they are bistatic fast backprojection (BiFBP) and bistatic fast factorized backprojection (BiFFBP). Both algorithms process radar echoes on a subaperture and subimage basis in order to minimize processing time. They are shown to work with any configuration of bistatic SAR. They also own time-domain characteristics, which are essential for UWB radar signal processing. BiFBP and BiFFBP are experimented successfully on the CARABAS-II simulated data.

    @Article{vuSjogrenPetterssonTAES2013BiFFBP,
    author = {Vu, Viet Thuy and Sjogren, Thomas K. and Pettersson, Mats I.},
    title = {Fast Time-Domain Algorithms for {UWB} Bistatic {SAR} Processing},
    journal = {IEEE Trans. Aerosp. Electron. Syst.},
    year = {2013},
    volume = {49},
    number = {3},
    pages = {1982-1994},
    month = jul,
    issn = {0018-9251},
    abstract = {Two fast time-domain algorithms are introduced for ultrawideband-ultrawidebeam (UWB) bistatic synthetic aperture radar (SAR) processing; they are bistatic fast backprojection (BiFBP) and bistatic fast factorized backprojection (BiFFBP). Both algorithms process radar echoes on a subaperture and subimage basis in order to minimize processing time. They are shown to work with any configuration of bistatic SAR. They also own time-domain characteristics, which are essential for UWB radar signal processing. BiFBP and BiFFBP are experimented successfully on the CARABAS-II simulated data.},
    doi = {10.1109/TAES.2013.6558032},
    file = {:vuSjogrenPetterssonTAES2013BiFFBP.pdf:PDF},
    keywords = {SAR Processing, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, Bistatic SAR, Bistatic Fast-Factorized Back-Projection, BiFFBP, radar cross-sections;radar imaging;synthetic aperture radar;time-domain analysis;ultra wideband radar;BiFFBP;CARABAS-II;UWB bistatic SAR;bistatic fast factorized backprojection;radar echo;radar signal processing;subaperture;subimage basis;synthetic aperture radar;time-domain algorithm;ultra wideband radar;ultra widebeam radar;Radar imaging;Receivers;Signal processing algorithms;Synthetic aperture radar;Time-domain analysis;Transmitters},
    pdf = {../../../docs/vuSjogrenPetterssonTAES2013BiFFBP.pdf},
    
    }
    


  36. Viet Thuy Vu, Thomas K. Sjogren, and Pettersson. Phase Error Calculation for Fast Time-Domain Bistatic SAR Algorithms. IEEE Trans. Aerosp. Electron. Syst., 49(1):631-639, 2013. Keyword(s): SAR Processing, Time-Domain Back-Projection, Back-Projection, TDBP, SAR image processing, Fast Factorized Back-Projection, FFBP, Bistatic SAR, Phase Error, Bistatic Fast Factorized Back-Projection, Motion Compensation, MoComp, Airborne SAR radar imaging, synthetic aperture radar, BiFFBP, SAR image quality, bistatic fast factorized backprojection, monostatic SAR, phase error calculation, synthetic aperture radar, time domain bistatic SAR, Apertures, Radar tracking, Receivers, Synthetic aperture radar, Target tracking, Transmitters CARABAS, LORA.
    Abstract: In synthetic aperture radar (SAR) processing, there is a trade-off between accuracy and speed. The approximations in an algorithm help to increase the algorithm's speed but cause deterministic phase errors which directly affect the SAR image quality. This paper discusses the phase error calculations for bistatic fast backprojection (BiFBP) and bistatic fast factorized backprojection (BiFFBP) which are essential for setting their parameters. The phase error calculation principle for bistatic SAR in comparison to monostatic SAR is presented. This principle is used to derive the maximum phase error equation.

    @Article{vuSjogrenPettersson2013BiFFBP,
    author = {Viet Thuy Vu and Sjogren, Thomas K. and Pettersson},
    journal = {IEEE Trans. Aerosp. Electron. Syst.},
    title = {Phase Error Calculation for Fast Time-Domain Bistatic SAR Algorithms},
    year = {2013},
    issn = {0018-9251},
    number = {1},
    pages = {631-639},
    volume = {49},
    abstract = {In synthetic aperture radar (SAR) processing, there is a trade-off between accuracy and speed. The approximations in an algorithm help to increase the algorithm's speed but cause deterministic phase errors which directly affect the SAR image quality. This paper discusses the phase error calculations for bistatic fast backprojection (BiFBP) and bistatic fast factorized backprojection (BiFFBP) which are essential for setting their parameters. The phase error calculation principle for bistatic SAR in comparison to monostatic SAR is presented. This principle is used to derive the maximum phase error equation.},
    doi = {10.1109/TAES.2013.6404127},
    file = {:vuSjogrenPettersson2013BiFFBP.pdf:PDF},
    keywords = {SAR Processing, Time-Domain Back-Projection, Back-Projection, TDBP, SAR image processing, Fast Factorized Back-Projection,FFBP, Bistatic SAR, Phase Error, Bistatic Fast Factorized Back-Projection, Motion Compensation, MoComp, Airborne SAR radar imaging;synthetic aperture radar;BiFFBP;SAR image quality;bistatic fast factorized backprojection;monostatic SAR;phase error calculation;synthetic aperture radar;time domain bistatic SAR;Apertures;Radar tracking;Receivers;Synthetic aperture radar;Target tracking;Transmitters CARABAS, LORA},
    pdf = {../../../docs/vuSjogrenPettersson2013BiFFBP.pdf},
    
    }
    


  37. Viet Thuy Vu, Thomas K. Sjogren, and Mats I. Pettersson. Phase Error Calculation for Fast Time-Domain Bistatic SAR Algorithms. IEEE Trans. Aerosp. Electron. Syst., 49(1):631-639, January 2013. Keyword(s): radar imaging, synthetic aperture radar, BiFFBP, SAR image quality, bistatic fast factorized backprojection, monostatic SAR, phase error calculation, synthetic aperture radar, time domain bistatic SAR, Apertures, Radar tracking, Receivers, Synthetic aperture radar, Target tracking, Transmitters.
    Abstract: In synthetic aperture radar (SAR) processing, there is a trade-off between accuracy and speed. The approximations in an algorithm help to increase the algorithm's speed but cause deterministic phase errors which directly affect the SAR image quality. This paper discusses the phase error calculations for bistatic fast backprojection (BiFBP) and bistatic fast factorized backprojection (BiFFBP) which are essential for setting their parameters. The phase error calculation principle for bistatic SAR in comparison to monostatic SAR is presented. This principle is used to derive the maximum phase error equation.

    @Article{vuSjogrenPetterssonTAES2014PhaseErrorBistatic,
    Title = {Phase Error Calculation for Fast Time-Domain Bistatic {SAR} Algorithms},
    Author = {Vu, Viet Thuy and Sjogren, Thomas K. and Pettersson, Mats I.},
    Doi = {10.1109/TAES.2013.6404127},
    ISSN = {0018-9251},
    Month = {Jan},
    Number = {1},
    Pages = {631-639},
    Volume = {49},
    Year = {2013},
    Abstract = {In synthetic aperture radar (SAR) processing, there is a trade-off between accuracy and speed. The approximations in an algorithm help to increase the algorithm's speed but cause deterministic phase errors which directly affect the SAR image quality. This paper discusses the phase error calculations for bistatic fast backprojection (BiFBP) and bistatic fast factorized backprojection (BiFFBP) which are essential for setting their parameters. The phase error calculation principle for bistatic SAR in comparison to monostatic SAR is presented. This principle is used to derive the maximum phase error equation.},
    Journal = {IEEE Trans. Aerosp. Electron. Syst.},
    Keywords = {radar imaging;synthetic aperture radar;BiFFBP;SAR image quality;bistatic fast factorized backprojection;monostatic SAR;phase error calculation;synthetic aperture radar;time domain bistatic SAR;Apertures;Radar tracking;Receivers;Synthetic aperture radar;Target tracking;Transmitters} 
    }
    


  38. Enes Yigit, Sevket Demirci, Caner Ozdemir, and Mustafa Tekbas. Short-range ground-based synthetic aperture radar imaging: performance comparison between frequency-wavenumber migration and back-projection algorithms. Journal of Applied Remote Sensing, 7(1):1-13, 2013. Keyword(s): GBSAR, SAR Processing, Ground-based SAR, Synthetic aperture radar, TDBP, Time-Domain Back-Projection, omega-k, Range Migration Algorithm, Wavenumber Domain Algorithm.
    Abstract: Two popular synthetic aperture radar (SAR) reconstruction algorithms, namely the back-projection (BP) and the frequency wavenumber (omega-k) algorithms, were tested and compared against each other, especially for their use in ground-based (GB) SAR applications directed to foreign object debris removal. For this purpose, an experimental setup in a semi-anechoic chamber room was accomplished to obtain near-field SAR images of objects on the ground. Then, the 90 to 95 GHz scattering data were acquired by using a stepped frequency continuous-wave radar operation. The performances of the setup and the imaging algorithms were then assessed by exploiting various metrics including point spread function, signal-to-clutter ratio, integrated side-lobe ratio, and computational complexity. Results demonstrate that although both algorithms produce almost accurate images of targets, the BP algorithm is shown to be superior to the omega-k algorithm due to its some inherent advantages specifically suited for short-range GB-SAR applications.

    @Article{yigitDemirciOzdemirTekbasJARS2013GBSAR,
    author = {Yigit, Enes and Demirci, Sevket and Ozdemir, Caner and Tekbas, Mustafa},
    title = {Short-range ground-based synthetic aperture radar imaging: performance comparison between frequency-wavenumber migration and back-projection algorithms},
    journal = {Journal of Applied Remote Sensing},
    year = {2013},
    volume = {7},
    number = {1},
    pages = {1-13},
    abstract = {Two popular synthetic aperture radar (SAR) reconstruction algorithms, namely the back-projection (BP) and the frequency wavenumber (omega-k) algorithms, were tested and compared against each other, especially for their use in ground-based (GB) SAR applications directed to foreign object debris removal. For this purpose, an experimental setup in a semi-anechoic chamber room was accomplished to obtain near-field SAR images of objects on the ground. Then, the 90 to 95 GHz scattering data were acquired by using a stepped frequency continuous-wave radar operation. The performances of the setup and the imaging algorithms were then assessed by exploiting various metrics including point spread function, signal-to-clutter ratio, integrated side-lobe ratio, and computational complexity. Results demonstrate that although both algorithms produce almost accurate images of targets, the BP algorithm is shown to be superior to the omega-k algorithm due to its some inherent advantages specifically suited for short-range GB-SAR applications.},
    doi = {10.1117/1.JRS.7.073483},
    file = {:yigitDemirciOzdemirTekbasJARS2013GBSAR.pdf:PDF},
    isbn = {1931-3195},
    keywords = {GBSAR, SAR Processing, Ground-based SAR, Synthetic aperture radar, TDBP, Time-Domain Back-Projection, omega-k, Range Migration Algorithm, Wavenumber Domain Algorithm},
    pdf = {../../../docs/yigitDemirciOzdemirTekbasJARS2013GBSAR.pdf},
    url = {http://dx.doi.org/10.1117/1.JRS.7.073483},
    
    }
    


  39. Bing Yu, Guoxiang Liu, Zhilin Li, Rui Zhang, Hongguo Jia, Xiaowen Wang, and Guolin Cai. Subsidence detection by TerraSAR-X interferometry on a network of natural persistent scatterers and artificial corner reflectors. Computers & Geosciences, 58:126-136, 2013.
    @Article{yuGuoxiangLiZhangJiaWangCai2013SubsidenceTerraSARX,
    author = {Yu, Bing and Liu, Guoxiang and Li, Zhilin and Zhang, Rui and Jia, Hongguo and Wang, Xiaowen and Cai, Guolin},
    title = {Subsidence detection by {TerraSAR-X} interferometry on a network of natural persistent scatterers and artificial corner reflectors},
    journal = {Computers \& Geosciences},
    year = {2013},
    volume = {58},
    pages = {126--136},
    owner = {ofrey},
    publisher = {Elsevier},
    
    }
    


  40. Lei Zhang, Hao-lin Li, Zhi-Jun Qiao, Meng-Dao Xing, and Zheng Bao. Integrating Autofocus Techniques With Fast Factorized Back-Projection for High-Resolution Spotlight SAR Imaging. IEEE Geosci. Remote Sens. Lett., 10(6):1394-1398, November 2013. Keyword(s): SAR Processing, Fast-Factorized Back-Projection, FFBP, Time-Domain Back-Projection, TDBP, Fourier transforms, geophysical techniques, remote sensing by radar, synthetic aperture radar, BP coordinate, BP imagery, FFBP SA images, FFBP recursion, FFBP sub-aperture images, Fourier transform, MAMD algorithm, MAMD recursion, conventional autofocus techniques integration, fast factorized back-projection, high efficiency FFBP, high precision FFBP, high-resolution SAR imaging, high-resolution spotlight SAR imaging, high-resolution synthetic aperture radar imaging, novel multiple aperture map drift algorithm, phase correction, phase error function, range-compressed phase history data, raw data, real data experiments, well-focused imagery, Apertures, Azimuth, Doppler effect, Fourier transforms, History, Signal processing algorithms, Synthetic aperture radar, Autofocus, back-projection (BP), fast factorized back-projection (FFBP), multiple aperture map drift (MAMD), synthetic aperture radar (SAR).
    Abstract: Back-projection (BP) is considered as an ideal methodology for the high-resolution synthetic aperture radar (SAR) imaging. However, applying conventional autofocus techniques to BP imagery requires a special consideration and is usually difficult to implement. In this letter, we present a scheme to compatibly blending a novel multiple aperture map drift (MAMD) algorithm with fast factorized back-projection (FFBP). Through an elaborate BP coordinate, we construct the Fourier transform relationship between FFBP sub-aperture (SA) images and the corresponding range-compressed phase history data. The phase error function is achieved by the MAMD within FFBP recursions, and well-focused imagery is obtained by phase correction on the range-compressed phase history data. The proposed scheme inherits the advantages of high precision and efficiency of the FFBP, and is suitable for high-resolution spotlight SAR imaging with raw data. Real data experiments guarantee the effectiveness of our proposed scheme.

    @Article{zhangLiQiaoXingBaoGRSL2013AutofocusFFBP,
    author = {Lei Zhang and Hao-lin Li and Zhi-Jun Qiao and Meng-Dao Xing and Zheng Bao},
    title = {Integrating Autofocus Techniques With Fast Factorized Back-Projection for High-Resolution Spotlight {SAR} Imaging},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2013},
    volume = {10},
    number = {6},
    pages = {1394-1398},
    month = nov,
    issn = {1545-598X},
    abstract = {Back-projection (BP) is considered as an ideal methodology for the high-resolution synthetic aperture radar (SAR) imaging. However, applying conventional autofocus techniques to BP imagery requires a special consideration and is usually difficult to implement. In this letter, we present a scheme to compatibly blending a novel multiple aperture map drift (MAMD) algorithm with fast factorized back-projection (FFBP). Through an elaborate BP coordinate, we construct the Fourier transform relationship between FFBP sub-aperture (SA) images and the corresponding range-compressed phase history data. The phase error function is achieved by the MAMD within FFBP recursions, and well-focused imagery is obtained by phase correction on the range-compressed phase history data. The proposed scheme inherits the advantages of high precision and efficiency of the FFBP, and is suitable for high-resolution spotlight SAR imaging with raw data. Real data experiments guarantee the effectiveness of our proposed scheme.},
    doi = {10.1109/LGRS.2013.2258886},
    file = {:zhangLiQiaoXingBaoGRSL2013AutofocusFFBP.pdf:PDF},
    keywords = {SAR Processing, Fast-Factorized Back-Projection, FFBP, Time-Domain Back-Projection, TDBP, Fourier transforms;geophysical techniques;remote sensing by radar;synthetic aperture radar;BP coordinate;BP imagery;FFBP SA images;FFBP recursion;FFBP sub-aperture images;Fourier transform;MAMD algorithm;MAMD recursion;conventional autofocus techniques integration;fast factorized back-projection;high efficiency FFBP;high precision FFBP;high-resolution SAR imaging;high-resolution spotlight SAR imaging;high-resolution synthetic aperture radar imaging;novel multiple aperture map drift algorithm;phase correction;phase error function;range-compressed phase history data;raw data;real data experiments;well-focused imagery;Apertures;Azimuth;Doppler effect;Fourier transforms;History;Signal processing algorithms;Synthetic aperture radar;Autofocus;back-projection (BP);fast factorized back-projection (FFBP);multiple aperture map drift (MAMD);synthetic aperture radar (SAR)},
    pdf = {../../../docs/zhangLiQiaoXingBaoGRSL2013AutofocusFFBP.pdf},
    
    }
    


  41. D. Zhu, R. Jiang, X. Mao, and Z. Zhu. Multi-Subaperture PGA for SAR Autofocusing. IEEE Transactions on Aerospace and Electronic Systems, 49(1):468-488, January 2013. Keyword(s): SAR Processing, Autofocus, synthetic aperture radar, SAR autofocusing, spotlight mode synthetic aperture radar, full-aperture phase gradient autofocus, PGA algorithm, high-order phase error, residual range cell migration, RCM, coherent processing interval, stripmap data, multisubaperture PGA algorithm, map drift technique, subaperture phase error, PGA-MD, Electronics packaging, Synthetic aperture radar, Azimuth, Image resolution, Accuracy, Polynomials, Estimation.
    Abstract: For spotlight mode synthetic aperture radar (SAR) autofocusing, the traditional full-aperture phase gradient autofocus (PGA) algorithm might suffer from performance degradation in the presence of significant high-order phase error and residual range cell migration (RCM), which tend to occur when the coherent processing interval (CPI) is long. Meanwhile, PGA does not perform satisfactorily when applied directly on the stripmap data. To address these shortcomings, we present a multi-subaperture PGA algorithm, which takes advantage of the map drift (MD) technique. It smoothly incorporates the estimation of residual RCM and combines the subaperture phase error (SPE) estimated by PGA in a very precise manner. The methodology and accuracy of PGA-MD are investigated in detail. Experimental results indicate the effectiveness of PGA-MD in both the spotlight and the stripmap modes.

    @Article{zhuJiangMaoZhuTAES2013MultiSubaperturePGAforSARAutofocusing,
    author = {D. {Zhu} and R. {Jiang} and X. {Mao} and Z. {Zhu}},
    journal = {IEEE Transactions on Aerospace and Electronic Systems},
    title = {Multi-Subaperture {PGA} for {SAR} Autofocusing},
    year = {2013},
    issn = {1557-9603},
    month = {Jan},
    number = {1},
    pages = {468-488},
    volume = {49},
    abstract = {For spotlight mode synthetic aperture radar (SAR) autofocusing, the traditional full-aperture phase gradient autofocus (PGA) algorithm might suffer from performance degradation in the presence of significant high-order phase error and residual range cell migration (RCM), which tend to occur when the coherent processing interval (CPI) is long. Meanwhile, PGA does not perform satisfactorily when applied directly on the stripmap data. To address these shortcomings, we present a multi-subaperture PGA algorithm, which takes advantage of the map drift (MD) technique. It smoothly incorporates the estimation of residual RCM and combines the subaperture phase error (SPE) estimated by PGA in a very precise manner. The methodology and accuracy of PGA-MD are investigated in detail. Experimental results indicate the effectiveness of PGA-MD in both the spotlight and the stripmap modes.},
    doi = {10.1109/TAES.2013.6404115},
    file = {:zhuJiangMaoZhuTAES2013MultiSubaperturePGAforSARAutofocusing.pdf:PDF},
    keywords = {SAR Processing, Autofocus, synthetic aperture radar;SAR autofocusing;spotlight mode synthetic aperture radar;full-aperture phase gradient autofocus;PGA algorithm;high-order phase error;residual range cell migration;RCM;coherent processing interval;stripmap data;multisubaperture PGA algorithm;map drift technique;subaperture phase error;PGA-MD;Electronics packaging;Synthetic aperture radar;Azimuth;Image resolution;Accuracy;Polynomials;Estimation},
    owner = {ofrey},
    
    }
    


Conference articles

  1. Kerry E. Dungan, LeRoy A. Gorham, and Linda J. Moore. SAR digital spotlight implementation in MATLAB. In Proc. SPIE, volume 8746, pages 1-11, 2013. Keyword(s): SAR Processing, Azimuth Focusing, Digital Spotlighting, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, MATLAB.
    Abstract: Legacy synthetic aperture radar (SAR) exploitation algorithms were image-based algorithms, designed to exploit complex and/or detected SAR imagery. In order to improve the efficiency of the algorithms, image chips, or region of interest (ROI) chips, containing candidate targets were extracted. These image chips were then used directly by exploitation algorithms for the purposes of target discrimination or identification. Recent exploitation research has suggested that performance can be improved by processing the underlying phase history data instead of standard SAR imagery. Digital Spotlighting takes the phase history data of a large image and extracts the phase history data corresponding to a smaller spatial subset of the image. In a typical scenario, this spotlighted phase history data will contain much fewer samples than the original data but will still result in an alias-free image of the ROI. The Digital Spotlight algorithm can be considered the first stage in a ``two-stage backprojection'' image formation process. As the first stage in two-stage backprojection, Digital Spotlighting filters the original phase history data into a number of ``pseudo''-phase histories that segment the scene into patches, each of which contain a reduced number of samples compared to the original data. The second stage of the imaging process consists of standard backprojection. The data rate reduction offered by Digital Spotlighting improves the computational efficiency of the overall imaging process by significantly reducing the total number of backprojection operations. This paper describes the Digital Spotlight algorithm in detail and provides an implementation in MATLAB.

    @InProceedings{dunganGorhamMooreSPIE2013DigitalSpotlightWithMatlabCode,
    author = {Dungan, Kerry E. and Gorham, LeRoy A. and Moore, Linda J.},
    title = {{SAR} digital spotlight implementation in {MATLAB}},
    booktitle = {Proc. SPIE},
    year = {2013},
    volume = {8746},
    pages = {1-11},
    abstract = {Legacy synthetic aperture radar (SAR) exploitation algorithms were image-based algorithms, designed to exploit complex and/or detected SAR imagery. In order to improve the efficiency of the algorithms, image chips, or region of interest (ROI) chips, containing candidate targets were extracted. These image chips were then used directly by exploitation algorithms for the purposes of target discrimination or identification. Recent exploitation research has suggested that performance can be improved by processing the underlying phase history data instead of standard SAR imagery. Digital Spotlighting takes the phase history data of a large image and extracts the phase history data corresponding to a smaller spatial subset of the image. In a typical scenario, this spotlighted phase history data will contain much fewer samples than the original data but will still result in an alias-free image of the ROI. The Digital Spotlight algorithm can be considered the first stage in a ``two-stage backprojection'' image formation process. As the first stage in two-stage backprojection, Digital Spotlighting filters the original phase history data into a number of ``pseudo''-phase histories that segment the scene into patches, each of which contain a reduced number of samples compared to the original data. The second stage of the imaging process consists of standard backprojection. The data rate reduction offered by Digital Spotlighting improves the computational efficiency of the overall imaging process by significantly reducing the total number of backprojection operations. This paper describes the Digital Spotlight algorithm in detail and provides an implementation in MATLAB.},
    doi = {10.1117/12.2020884},
    file = {:dunganGorhamMooreSPIE2013DigitalSpotlightWithMatlabCode.pdf:PDF},
    keywords = {SAR Processing, Azimuth Focusing, Digital Spotlighting, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, MATLAB},
    owner = {ofrey},
    pdf = {../../../docs/dunganGorhamMooreSPIE2013DigitalSpotlightWithMatlabCode.pdf},
    url = {https://doi.org/10.1117/12.2020884},
    
    }
    


  2. Othmar Frey, Irena Hajnsek, and Urs Wegmuller. Spaceborne SAR Tomography in Urban Areas. In Proc. IEEE Int. Geosci. Remote Sens. Symp., Melbourne, AUS, pages 69-72, July 2013. Keyword(s): SAR Processing, SAR Tomography, Tomography, SVD, truncated SVD, tikhonov regularization, PSI, Persistent Scatterer Interferometry, Spaceborne SAR, InSAR, DInSAR, geophysical image processing, geophysical techniques, radar interferometry, synthetic aperture radar, Bucarest, PanGEO, ENVISAT, ASAR, ENVISAT ASAR, interferometric technique, Differential SAR Interferometry, single polarization SAR, terrain deformation phenomena, Coherence, Correlation, Interferometry, Synthetic aperture radar, Vectors, Coherence, Terrain deformation, multi-baseline, Spaceborne SAR.
    Abstract: Persistent scatterer interferometry relies on the assumption that only one dominant scatterer is present per range-azimuth resolution cell. If this criterion is not met the point target candidate is discarded during the iterative processing sequence. This one-scatterer assumption contrasts with the fact that in urban scenarios layover is an ubiquitous phenomenon, and, therefore two or even more scatterers per resolution cell occur frequently. SAR tomography has the potential to support persistent scatterer interferometry in urban areas by providing a means to identify and separate two scatterers in elevation direction. In this paper, we explore an interferometric stack consisting of 25 ENVISAT/ASAR SLC images over Bucharest using SAR tomography approaches combined with interferometric point target processing. Elevation profiles are extracted using beamforming and truncated singular value decomposition focusing approaches.

    @InProceedings{freyHajnsekWegmullerIGARSS2013Tomo,
    author = {Frey, Othmar and Hajnsek, Irena and Wegmuller, Urs},
    title = {Spaceborne {SAR} Tomography in Urban Areas},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2013},
    pages = {69-72},
    address = {Melbourne, AUS},
    month = jul,
    abstract = {Persistent scatterer interferometry relies on the assumption that only one dominant scatterer is present per range-azimuth resolution cell. If this criterion is not met the point target candidate is discarded during the iterative processing sequence. This one-scatterer assumption contrasts with the fact that in urban scenarios layover is an ubiquitous phenomenon, and, therefore two or even more scatterers per resolution cell occur frequently. SAR tomography has the potential to support persistent scatterer interferometry in urban areas by providing a means to identify and separate two scatterers in elevation direction. In this paper, we explore an interferometric stack consisting of 25 ENVISAT/ASAR SLC images over Bucharest using SAR tomography approaches combined with interferometric point target processing. Elevation profiles are extracted using beamforming and truncated singular value decomposition focusing approaches.},
    doi = {10.1109/IGARSS.2013.6721094},
    file = {:freyHajnsekWegmullerIGARSS2013Tomo.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Tomography, SVD, truncated SVD, tikhonov regularization, PSI, Persistent Scatterer Interferometry, Spaceborne SAR, InSAR, DInSAR, geophysical image processing;geophysical techniques; radar interferometry; synthetic aperture radar;Bucarest;PanGEO; ENVISAT, ASAR, ENVISAT ASAR, interferometric technique; Differential SAR Interferometry; single polarization SAR;terrain deformation phenomena;Coherence;Correlation;Interferometry;Synthetic aperture radar;Vectors;Coherence;Terrain deformation;multi-baseline, Spaceborne SAR},
    owner = {ofrey},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyHajnsekWegmullerIGARSS2013Tomo.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6721094},
    
    }
    


  3. Othmar Frey, Charles L. Werner, Urs Wegmuller, Andreas Wiesmann, Daniel Henke, and Christophe Magnard. A car-borne SAR and InSAR experiment. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 93-96, 2013. Keyword(s): SAR Processing, Time-Domain Back-Projection, TDBP, dechirp-on-receive, FMCW, Frequency-modulated continous wave, Ground-based SAR, car-borne SAR, CARSAR, InSAR, DInSAR, geophysical techniques, ground-based SAR system, radar interferometry, synthetic aperture radar, GAMMA Portable Radar Interferometer (GPRI), GPRI, GPRI-II, PanGEO, interferometric technique, Coherence, Correlation, Interferometry, agile platform,.
    Abstract: In this contribution, a car-borne SAR and InSAR experiment is described. The slope of a valley was imaged by means of a single-pass InSAR system mounted on a car driving on roads along the bottom of the valley. The GAMMA portable radar interferometer {GPRI-II} hardware with a modified antenna configuration was used for data acquisition. The experimental setup (1), SAR imagery focused along a slightly curved sensor trajectory (2), and first interferometric results (3) obtained using this configuration are presented.

    @InProceedings{freyWernerWegmullerWiesmannHenkeMagnardIGARSS2013CARSAR,
    author = {Othmar Frey and Charles L. Werner and Urs Wegmuller and Andreas Wiesmann and Daniel Henke and Christophe Magnard},
    title = {A car-borne {SAR} and {InSAR} experiment},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2013},
    pages = {93-96},
    abstract = {In this contribution, a car-borne SAR and InSAR experiment is described. The slope of a valley was imaged by means of a single-pass InSAR system mounted on a car driving on roads along the bottom of the valley. The GAMMA portable radar interferometer {GPRI-II} hardware with a modified antenna configuration was used for data acquisition. The experimental setup (1), SAR imagery focused along a slightly curved sensor trajectory (2), and first interferometric results (3) obtained using this configuration are presented.},
    doi = {10.1109/IGARSS.2013.6721100},
    file = {:freyWernerWegmullerWiesmannHenkeMagnardIGARSS2013CARSAR.pdf:PDF},
    keywords = {SAR Processing, Time-Domain Back-Projection, TDBP, dechirp-on-receive, FMCW, Frequency-modulated continous wave, Ground-based SAR, car-borne SAR, CARSAR, InSAR, DInSAR,geophysical techniques; ground-based SAR system, radar interferometry;synthetic aperture radar; GAMMA Portable Radar Interferometer (GPRI), GPRI, GPRI-II,PanGEO; interferometric technique; Coherence;Correlation;Interferometry, agile platform,},
    owner = {ofrey},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyWernerWegmullerWiesmannHenkeMagnardIGARSS2013CARSAR.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6721100},
    
    }
    


  4. Giorgio Gomba, Michael Eineder, Thomas Fritz, and Alessandro Parizzi. Simulation of ionospheric effects on L-band synthetic aperture radar images. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 4463-4466, July 2013. Keyword(s): deformation, geophysical techniques, ionospheric electromagnetic wave propagation, radar imaging, radiowave propagation, remote sensing by radar, synthetic aperture radar, L-band mission, L-band synthetic aperture radar images, arbitrary ionospheric state, deformation measurements, disrupted raw images, focused images, ionosphere effect simulation, ionosphere estimation methods, ionosphere-free real SAR images, propagation delay errors, Abstracts, Ice, Ionosphere, Monitoring, Ionosphere, Ionospheric effects simulation, SAR Interferometry errors.
    Abstract: A procedure to simulate the effects of the ionosphere on Synthetic Aperture Radar (SAR) images is presented. The propagation delay errors induced by the ionosphere have to be compensated to millimeter level in order to meet the scientific requirements for an L-band mission dedicated to deformation measurements, which are summarized in [1]. The simulator presented in this paper can be used to study the effects of an arbitrary ionospheric state on SAR images and to generate disrupted raw and focused images starting from ionospherefree real SAR images and use them to validate ionosphere estimation methods.

    @InProceedings{gombaEinederFritzParizzi2013IonoSARSimulation,
    author = {Giorgio Gomba and Michael Eineder and Thomas Fritz and Alessandro Parizzi},
    title = {Simulation of ionospheric effects on {L}-band synthetic aperture radar images},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2013},
    pages = {4463--4466},
    month = jul,
    abstract = {A procedure to simulate the effects of the ionosphere on Synthetic Aperture Radar (SAR) images is presented. The propagation delay errors induced by the ionosphere have to be compensated to millimeter level in order to meet the scientific requirements for an L-band mission dedicated to deformation measurements, which are summarized in [1]. The simulator presented in this paper can be used to study the effects of an arbitrary ionospheric state on SAR images and to generate disrupted raw and focused images starting from ionospherefree real SAR images and use them to validate ionosphere estimation methods.},
    doi = {10.1109/IGARSS.2013.6723826},
    issn = {2153-6996},
    keywords = {deformation, geophysical techniques, ionospheric electromagnetic wave propagation, radar imaging, radiowave propagation, remote sensing by radar, synthetic aperture radar, L-band mission, L-band synthetic aperture radar images, arbitrary ionospheric state, deformation measurements, disrupted raw images, focused images, ionosphere effect simulation, ionosphere estimation methods, ionosphere-free real SAR images, propagation delay errors, Abstracts, Ice, Ionosphere, Monitoring, Ionosphere, Ionospheric effects simulation, SAR Interferometry errors},
    owner = {ofrey},
    
    }
    


  5. Stephan Palm, Anika Maresch, and Uwe Stilla. Investigation on Circular Mapping by FMCW-SAR on Small Airplanes. In International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-1/W1, ISPRS Hannover Workshop, 2013.
    Abstract: The evaluation of local damages after natural disasters by using remote sensing demands for flexible platforms as well as sensor systems,which guarantee both weather- and daylight-independence. Due to the fact of small energy consumption, small size and lightweight millimeter-wave FMCW radar sensors on small airplanes are very promising for this task. Especially in urban environments theside looking SAR geometry causes shadowing and foreshortening effects, which lead to gaps in the reconstructed scene and misinterpretation. Multiple views from different aspect angles can reduce the shadowing effects but especially in unknown areas the best lineof sight cannot be investigated in advance. This is achievable by performing circular flight trajectories. However, as millimeter-waveFMCW radar sensors typically have very narrow beams and small airplanes are sensitive to air turbulences, a beam stabilization method is necessary to provide full illumination of the target scene. In this paper the calculations for system specific optimal flight parameters are demonstrated and validated by simulations. The impact of air turbulences, causing angular deviations to the sensor and thus misplacementof the main beam lobe on the ground are explored by experimental data performed with our SUMATRA system. The effects of a potential mechanical beam stabilization are visualized and requirements for such a system are formulated. Our experiments showthat for typical flight conditions a stabilized platform is well suitable to stabilize a narrow radar beam in order to keep a target sceneconstantly illuminated over a full circular trajectory. Typically these stabilized platforms can handle angular corrections in all threegeometries (pitch, roll, squint) of up to 12 deg - 15 deg by a speed of 15 deg per second. Therefore a more cost intensive full gimbal systemwhich is known to be used in optical applications and which can handle a full 360 deg tracking is not neccessarily needed.

    @InProceedings{palmMareschStillaISPRS2013FMCWCircularSAR,
    author = {Stephan Palm and Anika Maresch and Uwe Stilla},
    booktitle = {International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-1/W1, ISPRS Hannover Workshop},
    title = {Investigation on Circular Mapping by {FMCW-SAR} on Small Airplanes},
    year = {2013},
    abstract = {The evaluation of local damages after natural disasters by using remote sensing demands for flexible platforms as well as sensor systems,which guarantee both weather- and daylight-independence. Due to the fact of small energy consumption, small size and lightweight millimeter-wave FMCW radar sensors on small airplanes are very promising for this task. Especially in urban environments theside looking SAR geometry causes shadowing and foreshortening effects, which lead to gaps in the reconstructed scene and misinterpretation. Multiple views from different aspect angles can reduce the shadowing effects but especially in unknown areas the best lineof sight cannot be investigated in advance. This is achievable by performing circular flight trajectories. However, as millimeter-waveFMCW radar sensors typically have very narrow beams and small airplanes are sensitive to air turbulences, a beam stabilization method is necessary to provide full illumination of the target scene. In this paper the calculations for system specific optimal flight parameters are demonstrated and validated by simulations. The impact of air turbulences, causing angular deviations to the sensor and thus misplacementof the main beam lobe on the ground are explored by experimental data performed with our SUMATRA system. The effects of a potential mechanical beam stabilization are visualized and requirements for such a system are formulated. Our experiments showthat for typical flight conditions a stabilized platform is well suitable to stabilize a narrow radar beam in order to keep a target sceneconstantly illuminated over a full circular trajectory. Typically these stabilized platforms can handle angular corrections in all threegeometries (pitch, roll, squint) of up to 12 deg - 15 deg by a speed of 15 deg per second. Therefore a more cost intensive full gimbal systemwhich is known to be used in optical applications and which can handle a full 360 deg tracking is not neccessarily needed.},
    owner = {ofrey},
    pdf = {../../../docs/palmMareschStillaISPRS2013FMCWCircularSAR.pdf},
    url = {https://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XL-1-W1/281/2013/isprsarchives-XL-1-W1-281-2013.pdf},
    
    }
    


  6. O. Ponce, P. Prats, R. Scheiber, A. Reigber, and A. Moreira. Analysis and optimization of multi-circular SAR for fully polarimetric holographic tomography over forested areas. In Proc. IEEE Int. Geoscience and Remote Sensing Symp. - IGARSS, pages 2365-2368, July 2013. Keyword(s): geophysical image processing, holography, radar imaging, radar polarimetry, synthetic aperture radar, vegetation, 3D resolution, DLR F-SAR sensor, GLRT algorithm, Germany, IRF, Kauf-beuren, L-band, acquisition geometry, anisotropic analysis, forested areas, fully polarimetric holographic tomography, generalized likelihood ratio test, holographic SAR tomograms, impulse response function, incoherent imaging, multicircular SAR analysis, multicircular SAR optimization, polarimetric MCSAR campaign, scatterers, sidelobe suppression, system bandwidth, Apertures, Bandwidth, Geometry, Image resolution, Imaging, L-band, Synthetic aperture radar, Anisotropy, compressive sensing (CS), fast factorized back-projection (FFBP), holographic tomography, multi-circular synthetic aperture radar (MCSAR), polarimetric synthetic aperture radar (PolSAR).
    @InProceedings{Ponce2013,
    author = {O. Ponce and P. Prats and R. Scheiber and A. Reigber and A. Moreira},
    title = {Analysis and optimization of multi-circular {SAR} for fully polarimetric holographic tomography over forested areas},
    booktitle = {Proc. IEEE Int. Geoscience and Remote Sensing Symp. - IGARSS},
    year = {2013},
    month = jul,
    pages = {2365--2368},
    doi = {10.1109/IGARSS.2013.6723294},
    issn = {2153-6996},
    keywords = {geophysical image processing, holography, radar imaging, radar polarimetry, synthetic aperture radar, vegetation, 3D resolution, DLR F-SAR sensor, GLRT algorithm, Germany, IRF, Kauf-beuren, L-band, acquisition geometry, anisotropic analysis, forested areas, fully polarimetric holographic tomography, generalized likelihood ratio test, holographic SAR tomograms, impulse response function, incoherent imaging, multicircular SAR analysis, multicircular SAR optimization, polarimetric MCSAR campaign, scatterers, sidelobe suppression, system bandwidth, Apertures, Bandwidth, Geometry, Image resolution, Imaging, L-band, Synthetic aperture radar, Anisotropy, compressive sensing (CS), fast factorized back-projection (FFBP), holographic tomography, multi-circular synthetic aperture radar (MCSAR), polarimetric synthetic aperture radar (PolSAR)},
    owner = {ofrey},
    
    }
    


  7. O. Ponce, P. Prats, R. Scheiber, A. Reigber, and A. Moreira. First demonstration of 3-D holographic tomography with fully polarimetric multi-circular SAR at L-band. In Proc. IEEE Int. Geoscience and Remote Sensing Symp. - IGARSS, pages 1127-1130, July 2013. Keyword(s): airborne radar, array signal processing, compressed sensing, geophysical image processing, holography, optical focusing, optical tomography, radar imaging, radar polarimetry, radar resolution, synthetic aperture radar, transient response, 3D holographic tomography, 3D polarimetric holographic tomogram, 3D sidelobe reduction, BF, CS, DLR F-SAR airborne system, Earth analysis, IRF, Kaufbeuren Germany, L-band, MCSAR, beamforming, coherent 3D radar backscattering, compressive sensing, dry soil, forested area, fully polarimetric multicircular SAR, ice, impulse response function, multiangular measurement acquisition, synthetic aperture radar, temporal decorrelation, volume scatterer, Apertures, Bandwidth, Image resolution, Imaging, L-band, Synthetic aperture radar, Vegetation, Circular synthetic aperture radar (CSAR), compressive sensing (CS), fast factorized back-projection (FFBP), holographic tomography, polarimetric synthetic aperture radar (PolSAR).
    @InProceedings{Ponce2013a,
    author = {O. Ponce and P. Prats and R. Scheiber and A. Reigber and A. Moreira},
    title = {First demonstration of {3-D} holographic tomography with fully polarimetric multi-circular {SAR} at L-band},
    booktitle = {Proc. IEEE Int. Geoscience and Remote Sensing Symp. - IGARSS},
    year = {2013},
    month = jul,
    pages = {1127--1130},
    doi = {10.1109/IGARSS.2013.6721363},
    issn = {2153-6996},
    keywords = {airborne radar, array signal processing, compressed sensing, geophysical image processing, holography, optical focusing, optical tomography, radar imaging, radar polarimetry, radar resolution, synthetic aperture radar, transient response, 3D holographic tomography, 3D polarimetric holographic tomogram, 3D sidelobe reduction, BF, CS, DLR F-SAR airborne system, Earth analysis, IRF, Kaufbeuren Germany, L-band, MCSAR, beamforming, coherent 3D radar backscattering, compressive sensing, dry soil, forested area, fully polarimetric multicircular SAR, ice, impulse response function, multiangular measurement acquisition, synthetic aperture radar, temporal decorrelation, volume scatterer, Apertures, Bandwidth, Image resolution, Imaging, L-band, Synthetic aperture radar, Vegetation, Circular synthetic aperture radar (CSAR), compressive sensing (CS), fast factorized back-projection (FFBP), holographic tomography, polarimetric synthetic aperture radar (PolSAR)},
    owner = {ofrey},
    
    }
    


  8. Marc Rodriguez-Cassola, Pau Prats-Iraola, Francesco De Zan, Rolf Scheiber, and Andreas Reigber. Doppler-related focusing aspects in the TOPS imaging mode. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 2043-2046, July 2013. Keyword(s): SAR Processing, TOPS, Terrain Observation by Progressive Scans, geophysical techniques, synthetic aperture radar, Doppler spectrum, ScanSAR, TOPS-mode SAR data focusing, TOPS-mode synthetic aperture radar data, Terrain Observation by Progressive Scans mode, azimuth baseband scaling operation, azimuth scaling factors, extended chirp scaling processing procedure, full-aperture imaging approach, limited azimuth-data extension, residual TOPS raw-data focusing, sliding spotlight SAR data focusing, spaceborne imaging mode, two-step focusing technique, wide-swath coverage, Azimuth, Bandwidth, Doppler effect, Focusing, Image resolution, Remote sensing, Aliasing, Terrain Observation by Progressive Scans (TOPS), deramp, extended chirp scaling, synthetic aperture radar (SAR).
    Abstract: The distortions caused in conventionally focused TOPS SAR images which originate from the azimuth-variant Doppler centroid within a burst are presented and analyzed. In particular, the azimuth distortions due to topography mismatch in focusing stages and the range distortions due to the assumption of validity for the stop-and-go approximation are expounded in detail. Compensation strategies to accommodate the two effects in an accurate and precise manner are discussed and validated with TOPS data acquired with TerraSAR-X.

    @InProceedings{rodriguezCassolaPratsDeZanScheiberReigberIGARSS2013TOPS,
    author = {Rodriguez-Cassola, Marc and Prats-Iraola, Pau and De Zan, Francesco and Scheiber, Rolf and Reigber, Andreas},
    title = {Doppler-related focusing aspects in the {TOPS} imaging mode},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2013},
    pages = {2043-2046},
    month = {July},
    abstract = {The distortions caused in conventionally focused TOPS SAR images which originate from the azimuth-variant Doppler centroid within a burst are presented and analyzed. In particular, the azimuth distortions due to topography mismatch in focusing stages and the range distortions due to the assumption of validity for the stop-and-go approximation are expounded in detail. Compensation strategies to accommodate the two effects in an accurate and precise manner are discussed and validated with TOPS data acquired with TerraSAR-X.},
    doi = {10.1109/IGARSS.2013.6723212},
    file = {:rodriguezCassolaPratsDeZanScheiberReigberIGARSS2013TOPS.pdf:PDF},
    issn = {2153-6996},
    keywords = {SAR Processing, TOPS, Terrain Observation by Progressive Scans,geophysical techniques;synthetic aperture radar;Doppler spectrum;ScanSAR;TOPS-mode SAR data focusing;TOPS-mode synthetic aperture radar data;Terrain Observation by Progressive Scans mode;azimuth baseband scaling operation;azimuth scaling factors;extended chirp scaling processing procedure;full-aperture imaging approach;limited azimuth-data extension;residual TOPS raw-data focusing;sliding spotlight SAR data focusing;spaceborne imaging mode;two-step focusing technique;wide-swath coverage;Azimuth;Bandwidth;Doppler effect;Focusing;Image resolution;Remote sensing;Aliasing;Terrain Observation by Progressive Scans (TOPS);deramp;extended chirp scaling;synthetic aperture radar (SAR)},
    pdf = {../../../docs/rodriguezCassolaPratsDeZanScheiberReigberIGARSS2013TOPS.pdf},
    
    }
    


  9. Stefano Tebaldini and Laurent Ferro-Famil. High resolution three-dimensional imaging of a snowpack from ground-based SAR data acquired at X and Ku Band. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 77-80, July 2013. Keyword(s): SAR Processing, SAR Tomography, Snow, Snowpack, X-band, Ku-band, remote sensing by radar, snow, synthetic aperture radar, 2D synthetic array, 3D imaging, AD 2010 12, Col de Porte, French Alps, GB SAR campaign, Ground Based SAR data, MeteoFrance, ice layer, snowpack, Backscatter, Focusing, Ice, Snow, Synthetic aperture radar.
    Abstract: In this paper we present experimental results relative to the vertical structure of a 60 cm snow-pack as sensed with X- and Ku-Band microwaves. The available data are from a Ground Based (GB) SAR campaign carried out by the University of Rennes I in December 2010 at Col de Porte, in the French Alps, in collaboration with Meteo-France. The data have been acquired by moving a VNA along two orthogonal directions, so as to obtain a two dimensional synthetic array. This allowed to focus the signal in the three dimensional space, thus providing a direct imaging of the vertical structure of the snow-pack at a resolution of few centimeters. Results revealed the presence of strong backscattering contributions from beneath the snow layer, that appear to be linked to the presence of an ice layer.

    @InProceedings{tebaldiniFerroFamil2013SnowTomo,
    author = {Stefano Tebaldini and Laurent Ferro-Famil},
    title = {High resolution three-dimensional imaging of a snowpack from ground-based {SAR} data acquired at {X} and {Ku} Band},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2013},
    pages = {77-80},
    month = jul,
    abstract = {In this paper we present experimental results relative to the vertical structure of a 60 cm snow-pack as sensed with X- and Ku-Band microwaves. The available data are from a Ground Based (GB) SAR campaign carried out by the University of Rennes I in December 2010 at Col de Porte, in the French Alps, in collaboration with Meteo-France. The data have been acquired by moving a VNA along two orthogonal directions, so as to obtain a two dimensional synthetic array. This allowed to focus the signal in the three dimensional space, thus providing a direct imaging of the vertical structure of the snow-pack at a resolution of few centimeters. Results revealed the presence of strong backscattering contributions from beneath the snow layer, that appear to be linked to the presence of an ice layer.},
    doi = {10.1109/IGARSS.2013.6721096},
    file = {:tebaldiniFerroFamil2013SnowTomo.pdf:PDF},
    issn = {2153-6996},
    keywords = {SAR Processing, SAR Tomography, Snow, Snowpack, X-band, Ku-band, remote sensing by radar;snow;synthetic aperture radar;2D synthetic array;3D imaging;AD 2010 12;Col de Porte;French Alps;GB SAR campaign;Ground Based SAR data;MeteoFrance;ice layer;snowpack;Backscatter;Focusing;Ice;Snow;Synthetic aperture radar},
    pdf = {../../../docs/tebaldiniFerroFamil2013SnowTomo.pdf},
    
    }
    


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This collection of SAR literature is far from being complete.
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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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