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Publications of year 2011

Articles in journal or book chapters

  1. S. Auer, S. Gernhardt, and Richard Bamler. Ghost Persistent Scatterers Related to Multiple Signal Reflections. IEEE Geosci. Remote Sens. Lett., 8(5):919-923, September 2011. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, 3D SAR simulation methods, SAR data stack, TerraSAR-X, building structures, ghost persistent scatterers, multiple signal reflections, persistent scatterer interferometry, reflection levels, synthetic aperture radar, geophysical image processing, geophysical techniques, remote sensing by radar, synthetic aperture radar;.
    Abstract: Persistent scatterer interferometry using stacks of very high resolution synthetic aperture radar (SAR) data reveals that single or even patterns of scatterers representing building structures may wrongly be localized below the ground level. In this letter, a case study on a test building model is presented using 3-D SAR simulation methods in order to explain the underlying localization problem. The case study indicates that Ghost-PSs are likely to be related to reflection levels that are higher than three. Moreover, the temporal stability of the amplitude of fivefold bounce signals is confirmed for a SAR data stack.

    @Article{auerGernhardtBamler2011,
    Title = {Ghost Persistent Scatterers Related to Multiple Signal Reflections},
    Author = {Auer, S. and Gernhardt, S. and Bamler, Richard},
    Doi = {10.1109/LGRS.2011.2134066},
    ISSN = {1545-598X},
    Month = sep,
    Number = {5},
    Pages = {919-923},
    Volume = {8},
    Year = {2011},
    Abstract = {Persistent scatterer interferometry using stacks of very high resolution synthetic aperture radar (SAR) data reveals that single or even patterns of scatterers representing building structures may wrongly be localized below the ground level. In this letter, a case study on a test building model is presented using 3-D SAR simulation methods in order to explain the underlying localization problem. The case study indicates that Ghost-PSs are likely to be related to reflection levels that are higher than three. Moreover, the temporal stability of the amplitude of fivefold bounce signals is confirmed for a SAR data stack.},
    Journal = {IEEE Geosci. Remote Sens. Lett.},
    Keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI,3D SAR simulation methods;SAR data stack;TerraSAR-X;building structures;ghost persistent scatterers;multiple signal reflections;persistent scatterer interferometry;reflection levels;synthetic aperture radar;geophysical image processing;geophysical techniques;remote sensing by radar;synthetic aperture radar;} 
    }
    


  2. A. Budillon, A. Evangelista, and G. Schirinzi. Three-Dimensional SAR Focusing From Multipass Signals Using Compressive Sampling. IEEE Trans. Geosci. Remote Sens., 49(1):488 -499, jan. 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, 3D SAR data imaging, SAR tomography, compressive sampling, image formation, multipass SAR data, multipass signals, optimization problem, spaced acquisition orbits, three-dimensional synthetic aperture radar, tomographic imaging, truncated singular value decomposition technique, image sampling, optimisation, radar imaging, synthetic aperture radar, tomography;.
    Abstract: Three-dimensional synthetic aperture radar (SAR) image formation provides the scene reflectivity estimation along azimuth, range, and elevation coordinates. It is based on multipass SAR data obtained usually by nonuniformly spaced acquisition orbits. A common 3-D SAR focusing approach is Fourier-based SAR tomography, but this technique brings about image quality problems because of the low number of acquisitions and their not regular spacing. Moreover, attained resolution in elevation is limited by the overall acquisitions baseline extent. In this paper, a novel 3-D SAR data imaging based on Compressive Sampling theory is presented. It is shown that since the image to be focused has usually a sparse representation along the elevation direction (i.e., only few scatterers with different elevation are present in the same range-azimuth resolution cell), it suffices to have a small number of measurements to construct the 3-D image. Furthermore, the method allows super-resolution imaging, overcoming the limitation imposed by the overall baseline span. Tomographic imaging is performed by solving an optimization problem which enforces sparsity through #x2113;1-norm minimization. Numerical results on simulated and real data validate the method and have been compared with the truncated singular value decomposition technique.

    @Article{5549892,
    author = {Budillon, A. and Evangelista, A. and Schirinzi, G.},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Three-Dimensional SAR Focusing From Multipass Signals Using Compressive Sampling},
    year = {2011},
    issn = {0196-2892},
    month = {jan.},
    number = {1},
    pages = {488 -499},
    volume = {49},
    abstract = {Three-dimensional synthetic aperture radar (SAR) image formation provides the scene reflectivity estimation along azimuth, range, and elevation coordinates. It is based on multipass SAR data obtained usually by nonuniformly spaced acquisition orbits. A common 3-D SAR focusing approach is Fourier-based SAR tomography, but this technique brings about image quality problems because of the low number of acquisitions and their not regular spacing. Moreover, attained resolution in elevation is limited by the overall acquisitions baseline extent. In this paper, a novel 3-D SAR data imaging based on Compressive Sampling theory is presented. It is shown that since the image to be focused has usually a sparse representation along the elevation direction (i.e., only few scatterers with different elevation are present in the same range-azimuth resolution cell), it suffices to have a small number of measurements to construct the 3-D image. Furthermore, the method allows super-resolution imaging, overcoming the limitation imposed by the overall baseline span. Tomographic imaging is performed by solving an optimization problem which enforces sparsity through #x2113;1-norm minimization. Numerical results on simulated and real data validate the method and have been compared with the truncated singular value decomposition technique.},
    doi = {10.1109/TGRS.2010.2054099},
    keywords = {SAR Processing, SAR Tomography, Tomography,3D SAR data imaging;SAR tomography;compressive sampling;image formation;multipass SAR data;multipass signals;optimization problem;spaced acquisition orbits;three-dimensional synthetic aperture radar;tomographic imaging;truncated singular value decomposition technique;image sampling;optimisation;radar imaging;synthetic aperture radar;tomography;},
    
    }
    


  3. Mariko S. Burgin, D. Clewley, R. M. Lucas, and Mahta Moghaddam. A Generalized Radar Backscattering Model Based on Wave Theory for Multilayer Multispecies Vegetation. IEEE Transactions on Geoscience and Remote Sensing, 49(12):4832-4845, December 2011. Keyword(s): backscatter, radar polarimetry, remote sensing by radar, vegetation, AIRSAR data, ALOS PALSAR, Advanced Land Observing Satellite, Airborne Synthetic Aperture Radar data, Australia, NASA JPL, NASA Jet Propulsion Laboratory, Phased Arrayed L-band Synthetic Aperture Radar data, Queensland, distorted Born approximation, generalized radar backscattering model, microwave interaction, multilayer multispecies vegetation, polarimetric radar backscattering coefficients, single species discrete scatterer model, soil moisture, structurally complex vegetation, surface model, surface roughness parameterization, two layer crown trunk models, wave theory, wooded savanna sites, Backscatter, Data models, Mathematical model, Scattering, Synthetic aperture radar, Vegetation, Forest scattering, multispecies vegetation, synthetic aperture radar (SAR) backscattering, wave theory.
    Abstract: A generalized radar scattering model based on wave theory is described. The model predicts polarimetric radar backscattering coefficients for structurally complex vegetation comprised of multiple species and layers. Compared to conventional two-layer crown-trunk models, modeling of actual forests has been improved substantially, allowing better understanding of microwave interaction with vegetation. The model generalizes an existing single-species discrete scatterer model and, by including scattering and propagation effects through judiciously defined vegetation layers, enables its application to an arbitrary number of species types. The scatterers within each layer are modeled as finite cylinders or disks having arbitrary size, density, and orientation, as in the predecessor model. The distorted Born approximation is used to represent the propagation through each layer, while scattering from each is modeled as a linear superposition of scattering from its respective random collection of scatterers. Interactions of waves within and between each layer and direct scattering from the ground are accounted for. Validation of the model is presented based on its application to 23 wooded savanna sites located in Queensland, Australia, and comparison with Advanced Land Observing Satellite (ALOS) Phased Arrayed L-band Synthetic Aperture Radar (PALSAR) and National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) Airborne Synthetic Aperture Radar (AIRSAR) data. Results indicate good agreement between simulated and actual backscattering coefficients, particularly at HH and VV polarizations. More discrepancies are found at HV polarizations and can be explained by uncertainties in the knowledge of input parameters, such as inaccuracies in the surface model, surface roughness parameterization, and soil moisture.

    @Article{burginClewleyLucasMoghaddamTGRS2011RadarBackscatterModelBasedonWaveTheoryForMultilayerMultispeciesVeg,
    author = {Mariko S. Burgin and D. Clewley and R. M. Lucas and Mahta Moghaddam},
    title = {A Generalized Radar Backscattering Model Based on Wave Theory for Multilayer Multispecies Vegetation},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2011},
    volume = {49},
    number = {12},
    pages = {4832-4845},
    month = dec,
    issn = {0196-2892},
    abstract = {A generalized radar scattering model based on wave theory is described. The model predicts polarimetric radar backscattering coefficients for structurally complex vegetation comprised of multiple species and layers. Compared to conventional two-layer crown-trunk models, modeling of actual forests has been improved substantially, allowing better understanding of microwave interaction with vegetation. The model generalizes an existing single-species discrete scatterer model and, by including scattering and propagation effects through judiciously defined vegetation layers, enables its application to an arbitrary number of species types. The scatterers within each layer are modeled as finite cylinders or disks having arbitrary size, density, and orientation, as in the predecessor model. The distorted Born approximation is used to represent the propagation through each layer, while scattering from each is modeled as a linear superposition of scattering from its respective random collection of scatterers. Interactions of waves within and between each layer and direct scattering from the ground are accounted for. Validation of the model is presented based on its application to 23 wooded savanna sites located in Queensland, Australia, and comparison with Advanced Land Observing Satellite (ALOS) Phased Arrayed L-band Synthetic Aperture Radar (PALSAR) and National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) Airborne Synthetic Aperture Radar (AIRSAR) data. Results indicate good agreement between simulated and actual backscattering coefficients, particularly at HH and VV polarizations. More discrepancies are found at HV polarizations and can be explained by uncertainties in the knowledge of input parameters, such as inaccuracies in the surface model, surface roughness parameterization, and soil moisture.},
    doi = {10.1109/TGRS.2011.2172949},
    file = {:burginClewleyLucasMoghaddamTGRS2011RadarBackscatterModelBasedonWaveTheoryForMultilayerMultispeciesVeg.pdf:PDF},
    keywords = {backscatter;radar polarimetry;remote sensing by radar;vegetation;AIRSAR data;ALOS PALSAR;Advanced Land Observing Satellite;Airborne Synthetic Aperture Radar data;Australia;NASA JPL;NASA Jet Propulsion Laboratory;Phased Arrayed L-band Synthetic Aperture Radar data;Queensland;distorted Born approximation;generalized radar backscattering model;microwave interaction;multilayer multispecies vegetation;polarimetric radar backscattering coefficients;single species discrete scatterer model;soil moisture;structurally complex vegetation;surface model;surface roughness parameterization;two layer crown trunk models;wave theory;wooded savanna sites;Backscatter;Data models;Mathematical model;Scattering;Synthetic aperture radar;Vegetation;Forest scattering;multispecies vegetation;synthetic aperture radar (SAR) backscattering;wave theory},
    
    }
    


  4. E.J. Candes and Y. Plan. A Probabilistic and RIPless Theory of Compressed Sensing. IEEE Transactions on Information Theory, 57(11):7235-7254, November 2011. Keyword(s): Fourier coefficients, Gaussian model, RIPless theory, compressed sensing, frequency measurements, probabilistic theory, probability distribution, restricted isometry property, signal random model, sparse signals, Fourier analysis, data compression, random processes, signal reconstruction, statistical distributions;.
    Abstract: This paper introduces a simple and very general theory of compressive sensing. In this theory, the sensing mechanism simply selects sensing vectors independently at random from a probability distribution F; it includes all standard models-e.g., Gaussian, frequency measurements-discussed in the literature, but also provides a framework for new measurement strategies as well. We prove that if the probability distribution F obeys a simple incoherence property and an isotropy property, one can faithfully recover approximately sparse signals from a minimal number of noisy measurements. The novelty is that our recovery results do not require the restricted isometry property (RIP) to hold near the sparsity level in question, nor a random model for the signal. As an example, the paper shows that a signal with s nonzero entries can be faithfully recovered from about s logn Fourier coefficients that are contaminated with noise.

    @Article{5967912,
    Title = {A Probabilistic and RIPless Theory of Compressed Sensing},
    Author = {Candes, E.J. and Plan, Y.},
    Doi = {10.1109/TIT.2011.2161794},
    ISSN = {0018-9448},
    Month = nov,
    Number = {11},
    Pages = {7235-7254},
    Volume = {57},
    Year = {2011},
    Abstract = {This paper introduces a simple and very general theory of compressive sensing. In this theory, the sensing mechanism simply selects sensing vectors independently at random from a probability distribution F; it includes all standard models-e.g., Gaussian, frequency measurements-discussed in the literature, but also provides a framework for new measurement strategies as well. We prove that if the probability distribution F obeys a simple incoherence property and an isotropy property, one can faithfully recover approximately sparse signals from a minimal number of noisy measurements. The novelty is that our recovery results do not require the restricted isometry property (RIP) to hold near the sparsity level in question, nor a random model for the signal. As an example, the paper shows that a signal with s nonzero entries can be faithfully recovered from about s logn Fourier coefficients that are contaminated with noise.},
    Journal = {IEEE Transactions on Information Theory},
    Keywords = {Fourier coefficients;Gaussian model;RIPless theory;compressed sensing;frequency measurements;probabilistic theory;probability distribution;restricted isometry property;signal random model;sparse signals;Fourier analysis;data compression;random processes;signal reconstruction;statistical distributions;} 
    }
    


  5. Hubert M.J. Cantalloube and Carole E. Nahum. Multiscale Local Map-Drift-Driven Multilateration SAR Autofocus Using Fast Polar Format Image Synthesis. IEEE Trans. Geosci. Remote Sens., 49(10):3730-3736, 2011. Keyword(s): SAR Processing, Autofocus, SAR Autofocus, MoComp, Motion Compensation, Map-Drift Autofocus, Multiscale Local Map-Drift, geophysical image processing, geophysical techniques, image registration, remote sensing by radar, synthetic aperture radar, SAR high-resolution imaging, autofocus method, bistatic errors, bistatic synthetic aperture radar autofocus, clock drift errors, coarse-to-fine resolution, fast polar format image synthesis, frequency-domain polar format algorithm, local images, multilateration, range-clipped Doppler low-filtered profiles, target points, Doppler effect, Equations, Image resolution, Optical transmitters, Receivers, Synthetic aperture radar, Trajectory, Airborne radar, bistatic synthetic aperture radar (SAR), focusing.
    Abstract: This new autofocus method is based on multilateration by ranging to small target areas at independent directions on the ground. Range-clipped Doppler low-filtered profiles around target points are used to compute local images using frequency-domain polar format algorithm. Images obtained from adjacent subapertures are registered, and the displacements yield elevation, trajectory, or clock drift (bistatic case) errors. To alleviate the insensitivity of map drift to error fluctuation faster than subaperture duration, the algorithm is reiterated with coarse-to-fine resolution, yielding high to low frequency errors. This allowed true bistatic synthetic aperture radar (SAR) autofocus (without monostatic image), autofocus in circular SAR on remote areas, and, as a side product, our first successful air-to-air inverse SAR high-resolution imaging.

    @Article{cantalloubeNahumTGRS2011Autofocus,
    author = {Cantalloube, Hubert M.J. and Nahum, Carole E.},
    title = {Multiscale Local Map-Drift-Driven Multilateration {SAR} Autofocus Using Fast Polar Format Image Synthesis},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2011},
    volume = {49},
    number = {10},
    pages = {3730-3736},
    issn = {0196-2892},
    abstract = {This new autofocus method is based on multilateration by ranging to small target areas at independent directions on the ground. Range-clipped Doppler low-filtered profiles around target points are used to compute local images using frequency-domain polar format algorithm. Images obtained from adjacent subapertures are registered, and the displacements yield elevation, trajectory, or clock drift (bistatic case) errors. To alleviate the insensitivity of map drift to error fluctuation faster than subaperture duration, the algorithm is reiterated with coarse-to-fine resolution, yielding high to low frequency errors. This allowed true bistatic synthetic aperture radar (SAR) autofocus (without monostatic image), autofocus in circular SAR on remote areas, and, as a side product, our first successful air-to-air inverse SAR high-resolution imaging.},
    doi = {10.1109/TGRS.2011.2161319},
    file = {:cantalloubeNahumTGRS2011Autofocus.pdf:PDF},
    keywords = {SAR Processing, Autofocus, SAR Autofocus, MoComp, Motion Compensation,Map-Drift Autofocus, Multiscale Local Map-Drift, geophysical image processing;geophysical techniques;image registration;remote sensing by radar;synthetic aperture radar;SAR high-resolution imaging;autofocus method;bistatic errors;bistatic synthetic aperture radar autofocus;clock drift errors;coarse-to-fine resolution;fast polar format image synthesis;frequency-domain polar format algorithm;local images;multilateration;range-clipped Doppler low-filtered profiles;target points;Doppler effect;Equations;Image resolution;Optical transmitters;Receivers;Synthetic aperture radar;Trajectory;Airborne radar;bistatic synthetic aperture radar (SAR);focusing},
    pdf = {../../../docs/cantalloubeNahumTGRS2011Autofocus.pdf},
    
    }
    


  6. M. C. Cuenca, A. J. Hooper, and Ramon F. Hanssen. A New Method for Temporal Phase Unwrapping of Persistent Scatterers InSAR Time Series. IEEE Trans. Geosci. Remote Sens., 49(11):4606-4615, November 2011. Keyword(s): Bayesian theory, InSAR time series, Southern Netherlands, persistent scatterer technique, probability density function, radar time series, spatially correlated information, temporal algorithm, temporal phase unwrapping, Bayes methods, geophysical image processing, radar imaging, radar interferometry, spatiotemporal phenomena, synthetic aperture radar, time series;.
    Abstract: The analysis of radar time series with persistent scatterer techniques usually relies on temporal unwrapping, because phase behavior can be often described by simple models. However, one of the major limitations of temporal algorithms is that they do not take advantage of spatially correlated information. Here, we focus on two types of information that can be spatially estimated, namely, observation precision and the probability density function of the model parameters. We introduce them in phase unwrapping using Bayesian theory. We test the proposed method using simulated data. We also apply them to a small area in the southern Netherlands and compare with conventional temporal unwrapping methods.

    @Article{cuencaHooperHanssen,
    Title = {A New Method for Temporal Phase Unwrapping of Persistent Scatterers InSAR Time Series},
    Author = {Cuenca, M. C. and Hooper, A. J. and Hanssen, Ramon F.},
    Doi = {10.1109/TGRS.2011.2143722},
    ISSN = {0196-2892},
    Month = nov,
    Number = {11},
    Pages = {4606-4615},
    Volume = {49},
    Year = {2011},
    Abstract = {The analysis of radar time series with persistent scatterer techniques usually relies on temporal unwrapping, because phase behavior can be often described by simple models. However, one of the major limitations of temporal algorithms is that they do not take advantage of spatially correlated information. Here, we focus on two types of information that can be spatially estimated, namely, observation precision and the probability density function of the model parameters. We introduce them in phase unwrapping using Bayesian theory. We test the proposed method using simulated data. We also apply them to a small area in the southern Netherlands and compare with conventional temporal unwrapping methods.},
    Journal = {IEEE Trans. Geosci. Remote Sens.},
    Keywords = {Bayesian theory;InSAR time series;Southern Netherlands;persistent scatterer technique;probability density function;radar time series;spatially correlated information;temporal algorithm;temporal phase unwrapping;Bayes methods;geophysical image processing;radar imaging;radar interferometry;spatiotemporal phenomena;synthetic aperture radar;time series;} 
    }
    


  7. Francesco De Zan and Paco Lopez-Dekker. SAR Image Stacking for the Exploitation of Long-Term Coherent Targets. IEEE Geosci. Remote Sens. Lett., 8(3):502-506, May 2011. Keyword(s): SAR Processing, interferometry, SAR interferometry, Stacking, covariance matrices, filtering theory, radar imaging, synthetic aperture radar, SAR image stacking, long-term coherent targets, synthetic aperture radar images, coherent temporal filtering, signal to noise ratio, TerraSAR-X data, long-term interferograms, covariance matrix, Coherence, Interferometry, Decorrelation, Estimation, Noise, Stacking, Synthetic aperture radar, Synthetic aperture radar interferometry.
    Abstract: This letter shows that in a repeat-pass data set of synthetic aperture radar (SAR) images, a long-term coherent component, when present, can be recovered by coherent temporal filtering of the SAR images and can successively form interferograms with higher signal-to-noise ratio. The validity of the idea is confirmed through simulations and one example with real TerraSAR-X data. The theoretical necessity of using long-term interferograms is also discussed and linked to autoregressive processes, starting from the observation that the optimal weighting is given by the inverse of the covariance matrix.

    @Article{deZanLopezDekkerGRSL2011InSARStackingLongTimeSeries,
    author = {{De Zan}, Francesco and {Lopez-Dekker},Paco},
    title = {{SAR} Image Stacking for the Exploitation of Long-Term Coherent Targets},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2011},
    volume = {8},
    number = {3},
    pages = {502-506},
    month = may,
    issn = {1545-598X},
    abstract = {This letter shows that in a repeat-pass data set of synthetic aperture radar (SAR) images, a long-term coherent component, when present, can be recovered by coherent temporal filtering of the SAR images and can successively form interferograms with higher signal-to-noise ratio. The validity of the idea is confirmed through simulations and one example with real TerraSAR-X data. The theoretical necessity of using long-term interferograms is also discussed and linked to autoregressive processes, starting from the observation that the optimal weighting is given by the inverse of the covariance matrix.},
    doi = {10.1109/LGRS.2010.2089494},
    file = {:deZanLopezDekkerGRSL2011InSARStackingLongTimeSeries.pdf:PDF},
    keywords = {SAR Processing, interferometry, SAR interferometry, Stacking, covariance matrices;filtering theory;radar imaging;synthetic aperture radar;SAR image stacking;long-term coherent targets;synthetic aperture radar images;coherent temporal filtering;signal to noise ratio;TerraSAR-X data;long-term interferograms;covariance matrix;Coherence;Interferometry;Decorrelation;Estimation;Noise;Stacking;Synthetic aperture radar;Synthetic aperture radar interferometry},
    owner = {ofrey},
    
    }
    


  8. Francesco De Zan and Paco López-Dekker. SAR Image Stacking for the Exploitation of Long-Term Coherent Targets. IEEE Geosci. Remote Sens. Lett., 8(3):502-506, May 2011. Keyword(s): SAR Processing, SAR interferometry, Interferometry, differential interferometry, InSAR, DInSAR, Coherence, Decorrelation, Estimation, Interferometry, Noise, Stacking, Synthetic aperture radar, covariance matrices, filtering theory, radar imaging, synthetic aperture radar, SAR image stacking, TerraSAR-X data, coherent temporal filtering, covariance matrix, long-term coherent targets, long-term interferograms, signal to noise ratio, synthetic aperture radar images, Synthetic aperture radar interferometry;.
    Abstract: This letter shows that in a repeat-pass data set of synthetic aperture radar (SAR) images, a long-term coherent component, when present, can be recovered by coherent temporal filtering of the SAR images and can successively form interferograms with higher signal-to-noise ratio. The validity of the idea is confirmed through simulations and one example with real TerraSAR-X data. The theoretical necessity of using long-term interferograms is also discussed and linked to autoregressive processes, starting from the observation that the optimal weighting is given by the inverse of the covariance matrix.

    @Article{deZanLopezDekkerGRSL2011,
    author = {De Zan, Francesco and L\'opez-Dekker, Paco},
    title = {SAR Image Stacking for the Exploitation of Long-Term Coherent Targets},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2011},
    volume = {8},
    number = {3},
    pages = {502-506},
    month = may,
    issn = {1545-598X},
    abstract = {This letter shows that in a repeat-pass data set of synthetic aperture radar (SAR) images, a long-term coherent component, when present, can be recovered by coherent temporal filtering of the SAR images and can successively form interferograms with higher signal-to-noise ratio. The validity of the idea is confirmed through simulations and one example with real TerraSAR-X data. The theoretical necessity of using long-term interferograms is also discussed and linked to autoregressive processes, starting from the observation that the optimal weighting is given by the inverse of the covariance matrix.},
    doi = {10.1109/LGRS.2010.2089494},
    file = {:deZanLopezDekkerGRSL2011.pdf:PDF},
    keywords = {SAR Processing, SAR interferometry, Interferometry, differential interferometry, InSAR, DInSAR,Coherence;Decorrelation;Estimation;Interferometry;Noise;Stacking;Synthetic aperture radar;covariance matrices;filtering theory; radar imaging;synthetic aperture radar;SAR image stacking;TerraSAR-X data;coherent temporal filtering;covariance matrix; long-term coherent targets;long-term interferograms;signal to noise ratio;synthetic aperture radar images;Synthetic aperture radar interferometry;},
    pdf = {../../../docs/deZanLopezDekkerGRSL2011.pdf},
    
    }
    


  9. M. Eineder, C. Minet, P. Steigenberger, Xiaoying Cong, and T. Fritz. Imaging Geodesy: Toward Centimeter-Level Ranging Accuracy With TerraSAR-X. IEEE Transactions on Geoscience and Remote Sensing, 49(2):661-671, February 2011. Keyword(s): TerraSAR-X radar image, corner reflector technique, geodesy imaging method, glacier measurement, image correlation technique, large-scale Earth surface displacement, solid Earth tide motion vector, spaceborne radar amplitude image, synthetic aperture radar image correlation technique, tropospheric water vapor variation, volcano measurement, geodesy, geophysical image processing, geophysical techniques, ionosphere, radar imaging, remote sensing by radar, synthetic aperture radar, tides, troposphere.
    Abstract: In this paper, we report on experiments to measure large-scale Earth surface displacements, such as those caused by solid Earth tides, with centimeter-level accuracy using TerraSAR-X radar images. With two totally different approaches, corner reflectors and image correlation techniques, we show the clear interrelation between the radar range measurements and the projection of the solid Earth tide motion vector onto the radar line of sight. Pixel location accuracies of up to 2.6-cm standard deviation can be achieved after a single calibration. We further demonstrate that solid Earth tides and tropospheric water vapor variations are the largest sources of ranging error if not compensated for. Alternatively, tropospheric water vapor can be estimated with centimeter accuracy using our proposed technique of synthetic aperture radar (SAR) image correlation and solid Earth motion compensation by the existing models. We also consider ionospheric delays which improve the results marginally in the X-band. Our results show the best ranging accuracies so far reported for spaceborne radar amplitude images and make TerraSAR-X-together with our simple compensation methodology-suitable for the imaging of centimeter-level Earth displacements. Absolute measurements of volcanoes or glaciers are possible without the use of ground equipment and without the use of SAR interferometry, thus avoiding the associated problems of phase ambiguity, phase unwrapping, and reference points.

    @Article{einederMinetSteigenbergerXiaoyingCongFritz2011,
    author = {Eineder, M. and Minet, C. and Steigenberger, P. and Xiaoying Cong and Fritz, T.},
    title = {Imaging Geodesy: Toward Centimeter-Level Ranging Accuracy With {TerraSAR-X}},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2011},
    volume = {49},
    number = {2},
    pages = {661-671},
    month = feb,
    issn = {0196-2892},
    abstract = {In this paper, we report on experiments to measure large-scale Earth surface displacements, such as those caused by solid Earth tides, with centimeter-level accuracy using TerraSAR-X radar images. With two totally different approaches, corner reflectors and image correlation techniques, we show the clear interrelation between the radar range measurements and the projection of the solid Earth tide motion vector onto the radar line of sight. Pixel location accuracies of up to 2.6-cm standard deviation can be achieved after a single calibration. We further demonstrate that solid Earth tides and tropospheric water vapor variations are the largest sources of ranging error if not compensated for. Alternatively, tropospheric water vapor can be estimated with centimeter accuracy using our proposed technique of synthetic aperture radar (SAR) image correlation and solid Earth motion compensation by the existing models. We also consider ionospheric delays which improve the results marginally in the X-band. Our results show the best ranging accuracies so far reported for spaceborne radar amplitude images and make TerraSAR-X-together with our simple compensation methodology-suitable for the imaging of centimeter-level Earth displacements. Absolute measurements of volcanoes or glaciers are possible without the use of ground equipment and without the use of SAR interferometry, thus avoiding the associated problems of phase ambiguity, phase unwrapping, and reference points.},
    doi = {10.1109/TGRS.2010.2060264},
    file = {:einederMinetSteigenbergerXiaoyingCongFritz2011.pdf:PDF},
    keywords = {TerraSAR-X radar image;corner reflector technique;geodesy imaging method;glacier measurement;image correlation technique;large-scale Earth surface displacement;solid Earth tide motion vector;spaceborne radar amplitude image;synthetic aperture radar image correlation technique;tropospheric water vapor variation;volcano measurement;geodesy;geophysical image processing;geophysical techniques;ionosphere;radar imaging;remote sensing by radar;synthetic aperture radar;tides;troposphere},
    pdf = {../../../docs/einederMinetSteigenbergerXiaoyingCongFritz2011.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5570983},
    
    }
    


  10. A. Elsherbini and K. Sarabandi. Dual-Polarized Coupled Sectorial Loop Antennas for UWB Applications. IEEE_J_AWPL, 10:75-78, 2011. Keyword(s): antenna feeds, antenna radiation patterns, directive antennas, electromagnetic wave polarisation, loop antennas, radar antennas, ultra wideband antennas, ultra wideband communication, ultra wideband radar, communications applications, compact dual-polarized UWB antennas, coupled sectorial loop antenna concept, crossed dipole configuration, directional dual-polarized cavity-backed asymmetric CSLA, dual-polarized coupled sectorial loop antennas, integrated balun feed, planar CSLA, radar applications, Antenna measurements, Cavity resonators, Directive antennas, Feeds, Impedance matching, Ultra wideband antennas, Dual-polarized antenna, radar antenna, ultrawideband (UWB) antenna.
    @Article{Elsherbini2011f,
    author = {A. Elsherbini and K. Sarabandi},
    title = {Dual-Polarized Coupled Sectorial Loop Antennas for {UWB} Applications},
    journal = IEEE_J_AWPL,
    year = {2011},
    volume = {10},
    pages = {75--78},
    issn = {1536-1225},
    doi = {10.1109/LAWP.2011.2109366},
    keywords = {antenna feeds, antenna radiation patterns, directive antennas, electromagnetic wave polarisation, loop antennas, radar antennas, ultra wideband antennas, ultra wideband communication, ultra wideband radar, communications applications, compact dual-polarized UWB antennas, coupled sectorial loop antenna concept, crossed dipole configuration, directional dual-polarized cavity-backed asymmetric CSLA, dual-polarized coupled sectorial loop antennas, integrated balun feed, planar CSLA, radar applications, Antenna measurements, Cavity resonators, Directive antennas, Feeds, Impedance matching, Ultra wideband antennas, Dual-polarized antenna, radar antenna, ultrawideband (UWB) antenna},
    owner = {ofrey},
    
    }
    


  11. Geir Engen and Yngvar Larsen. Efficient Full Aperture Processing of TOPS Mode Data Using the Moving Band Chirp Z -Transform. IEEE Trans. Geosci. Remote Sens., 49(10):3688-3693, October 2011. Keyword(s): SAR Processing, TOPS, Terrain Observation by Progressive Scans, Z transforms, artificial satellites, satellite communication, European Space Agency, Sentinel-1 operational satellite, TOPS mode data, Terrain Observation by Progressive Scans, azimuth aperture, full aperture processing, imaging mode, moving band chirp Z-transform, signal transform, wavenumber domain processor, Antennas, Azimuth, Bandwidth, Chirp, Doppler effect, Focusing, Time frequency analysis, SAR processing, synthetic aperture radar (SAR), terrain observation by progressive scans (TOPS).
    Abstract: The main operational mode of the European Space Agency's upcoming Sentinel-1 operational satellite will be the Terrain Observation by Progressive Scans (TOPS) imaging mode. This paper presents a very efficient wavenumber domain processor for the processing of TOPS mode data. In particular, a novel signal transform, called a moving band chirp Z-transform, is introduced in order to allow the entire azimuth aperture to be focused simultaneously without any need for temporary unaliasing, which requires upsampling, or subaperture processing.

    @Article{engenLarsenTGARS2011TOPSwithChirpZTransform,
    author = {Engen, Geir and Larsen, Yngvar},
    title = {Efficient Full Aperture Processing of {TOPS} Mode Data Using the Moving Band Chirp {Z} -Transform},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2011},
    volume = {49},
    number = {10},
    pages = {3688-3693},
    month = {Oct},
    issn = {0196-2892},
    abstract = {The main operational mode of the European Space Agency's upcoming Sentinel-1 operational satellite will be the Terrain Observation by Progressive Scans (TOPS) imaging mode. This paper presents a very efficient wavenumber domain processor for the processing of TOPS mode data. In particular, a novel signal transform, called a moving band chirp Z-transform, is introduced in order to allow the entire azimuth aperture to be focused simultaneously without any need for temporary unaliasing, which requires upsampling, or subaperture processing.},
    doi = {10.1109/TGRS.2011.2145384},
    file = {:engenLarsenTGARS2011TOPSwithChirpZTransform.pdf:PDF},
    keywords = {SAR Processing, TOPS, Terrain Observation by Progressive Scans, Z transforms;artificial satellites;satellite communication;European Space Agency;Sentinel-1 operational satellite;TOPS mode data;Terrain Observation by Progressive Scans;azimuth aperture;full aperture processing;imaging mode;moving band chirp Z-transform;signal transform;wavenumber domain processor;Antennas;Azimuth;Bandwidth;Chirp;Doppler effect;Focusing;Time frequency analysis;SAR processing;synthetic aperture radar (SAR);terrain observation by progressive scans (TOPS)},
    pdf = {../../../docs/engenLarsenTGARS2011TOPSwithChirpZTransform.pdf},
    
    }
    


  12. A. Ferretti, A. Fumagalli, F. Novali, C. Prati, F. Rocca, and A. Rucci. A New Algorithm for Processing Interferometric Data-Stacks: SqueeSAR. IEEE Trans. Geosci. Remote Sens., 49(9):3460-3470, September 2011. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, Alpine area, PSInSAR, SqueeSAR, city, coherence matrix, coherent radar targets, distributed scatterers, geophysical parameters, high phase stability, interferograms, interferometric data-stacks processing algorithm, man-made objects, permanent scatterer SAR interferometry, point-wise objects, statistical behavior, data analysis, geophysical techniques, radar interferometry, radar signal processing, remote sensing by radar, synthetic aperture radar;.
    Abstract: Permanent Scatterer SAR Interferometry (PSInSAR) aims to identify coherent radar targets exhibiting high phase stability over the entire observation time period. These targets often correspond to point-wise, man-made objects widely available over a city, but less present in non-urban areas. To overcome the limits of PSInSAR, analysis of interferometric data-stacks should aim at extracting geophysical parameters not only from point-wise deterministic objects (i.e., PS), but also from distributed scatterers (DS). Rather than developing hybrid processing chains where two or more algorithms are applied to the same data-stack, and results are then combined, in this paper we introduce a new approach, SqueeSAR, to jointly process PS and DS, taking into account their different statistical behavior. As it will be shown, PS and DS can be jointly processed without the need for significant changes to the traditional PSInSAR processing chain and without the need to unwrap hundreds of interferograms, provided that the coherence matrix associated with each DS is properly squeezed to provide a vector of optimum (wrapped) phase values. Results on real SAR data, acquired over an Alpine area, challenging for any InSAR analysis, confirm the effectiveness of this new approach.

    @Article{ferrettiFumagalliNovaliPratiRoccaRucci2011PSISqueeSAR,
    author = {Ferretti, A. and Fumagalli, A. and Novali, F. and Prati, C. and Rocca, F. and Rucci, A.},
    title = {A New Algorithm for Processing Interferometric Data-Stacks: {SqueeSAR}},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2011},
    volume = {49},
    number = {9},
    pages = {3460-3470},
    month = sep,
    issn = {0196-2892},
    abstract = {Permanent Scatterer SAR Interferometry (PSInSAR) aims to identify coherent radar targets exhibiting high phase stability over the entire observation time period. These targets often correspond to point-wise, man-made objects widely available over a city, but less present in non-urban areas. To overcome the limits of PSInSAR, analysis of interferometric data-stacks should aim at extracting geophysical parameters not only from point-wise deterministic objects (i.e., PS), but also from distributed scatterers (DS). Rather than developing hybrid processing chains where two or more algorithms are applied to the same data-stack, and results are then combined, in this paper we introduce a new approach, SqueeSAR, to jointly process PS and DS, taking into account their different statistical behavior. As it will be shown, PS and DS can be jointly processed without the need for significant changes to the traditional PSInSAR processing chain and without the need to unwrap hundreds of interferograms, provided that the coherence matrix associated with each DS is properly squeezed to provide a vector of optimum (wrapped) phase values. Results on real SAR data, acquired over an Alpine area, challenging for any InSAR analysis, confirm the effectiveness of this new approach.},
    doi = {10.1109/TGRS.2011.2124465},
    file = {:ferrettiFumagalliNovaliPratiRoccaRucci2011PSISqueeSAR.pdf:PDF},
    keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI, Alpine area;PSInSAR;SqueeSAR;city;coherence matrix;coherent radar targets;distributed scatterers;geophysical parameters;high phase stability;interferograms;interferometric data-stacks processing algorithm;man-made objects;permanent scatterer SAR interferometry;point-wise objects;statistical behavior;data analysis;geophysical techniques;radar interferometry;radar signal processing;remote sensing by radar;synthetic aperture radar;},
    pdf = {../../../docs/ferrettiFumagalliNovaliPratiRoccaRucci2011PSISqueeSAR.pdf},
    
    }
    


  13. G. Fornaro, A. Pauciullo, and D. Reale. A Null-Space Method for the Phase Unwrapping of Multitemporal SAR Interferometric Stacks. IEEE Transactions on Geoscience and Remote Sensing, 49(6):2323-2334, June 2011. Keyword(s): SAR Processing, DInSAR, SAR Interferometry, Phase unwrapping, 2-D azimuth-range domain, Earth surface displacement, MCF algorithm, data analysis, full 3-D unwrapping method, interferogram generation scheme, interferogram spatial structure, multitemporal SAR interferometric stack analysis, multitemporal differential interferometric synthetic aperture radar analysis, null-space method, optimization technique, phase unwrapping method, spatial baseline domain, time series, unrestricted phase signal reconstruction, data analysis, geophysical techniques, radar interferometry, synthetic aperture radar, time series, topography (Earth).
    Abstract: Multitemporal differential interferometric synthetic aperture radar analysis is of fundamental importance in the monitoring of Earth surface displacements. In this context, a key role for the reconstruction of the deformation maps and time series is played by the phase unwrapping (PhU) that reconstructs the unrestricted phase signals starting from the measured wrapped versions, i.e., the interferograms. PhU is typically carried out independently for each interferogram in the 2-D azimuth-range domain via the efficient minimum cost flow (MCF) optimization technique. Recently, it has been proposed a two-step (TS) strategy that exploits both the temporal and the spatial structures of the available interferograms. The MCF algorithm is applied in this case also in the temporal/spatial baseline domain, and this step is combined with the classical 2-D space unwrapping. However, the restriction on the use of the MCF algorithm in the baseline domain poses limitations on the interferogram generation scheme. We present a formulation which makes use of the overdetermined nature of the operator that relates the phase differences to the absolute phase values: the problem is addressed in a more general framework that can cope with the 3-D (2-D space and time) nature of the data. This formulation is derived with reference to the sequential (TS) approach to overcome its restrictions on the interferogram generation. The new algorithm is validated on both simulated and real data. Moreover, the use of this new formulation for a full 3-D unwrapping is also addressed.

    @Article{fornaroPauciulloRealeTGRS2011PhaseUnwrapInSARStacks,
    Title = {A Null-Space Method for the Phase Unwrapping of Multitemporal {SAR} Interferometric Stacks},
    Author = {Fornaro, G. and Pauciullo, A. and Reale, D.},
    Doi = {10.1109/TGRS.2010.2102767},
    ISSN = {0196-2892},
    Month = jun,
    Number = {6},
    Pages = {2323-2334},
    Volume = {49},
    Year = {2011},
    Abstract = {Multitemporal differential interferometric synthetic aperture radar analysis is of fundamental importance in the monitoring of Earth surface displacements. In this context, a key role for the reconstruction of the deformation maps and time series is played by the phase unwrapping (PhU) that reconstructs the unrestricted phase signals starting from the measured wrapped versions, i.e., the interferograms. PhU is typically carried out independently for each interferogram in the 2-D azimuth-range domain via the efficient minimum cost flow (MCF) optimization technique. Recently, it has been proposed a two-step (TS) strategy that exploits both the temporal and the spatial structures of the available interferograms. The MCF algorithm is applied in this case also in the temporal/spatial baseline domain, and this step is combined with the classical 2-D space unwrapping. However, the restriction on the use of the MCF algorithm in the baseline domain poses limitations on the interferogram generation scheme. We present a formulation which makes use of the overdetermined nature of the operator that relates the phase differences to the absolute phase values: the problem is addressed in a more general framework that can cope with the 3-D (2-D space and time) nature of the data. This formulation is derived with reference to the sequential (TS) approach to overcome its restrictions on the interferogram generation. The new algorithm is validated on both simulated and real data. Moreover, the use of this new formulation for a full 3-D unwrapping is also addressed.},
    Journal = {IEEE Transactions on Geoscience and Remote Sensing},
    Keywords = {SAR Processing, DInSAR, SAR Interferometry, Phase unwrapping, 2-D azimuth-range domain;Earth surface displacement;MCF algorithm;data analysis;full 3-D unwrapping method;interferogram generation scheme;interferogram spatial structure;multitemporal SAR interferometric stack analysis;multitemporal differential interferometric synthetic aperture radar analysis;null-space method;optimization technique;phase unwrapping method;spatial baseline domain;time series;unrestricted phase signal reconstruction;data analysis;geophysical techniques;radar interferometry;synthetic aperture radar;time series;topography (Earth)} 
    }
    


  14. Othmar Frey and Erich Meier. 3-D Time-Domain SAR Imaging of a Forest Using Airborne Multibaseline Data at L- and P-Bands. IEEE Trans. Geosci. Remote Sens., 49(10):3660-3664, October 2011. Keyword(s): Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, synthetic aperture radar, SAR, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation.
    Abstract: In this paper, a time-domain back-projection based tomographic processing approach to a 3-D reconstruction grid is detailed, with the focusing in the third dimension being either modified versions of multilook standard beamforming, robust Capon beamforming, or multiple signal classification. The novel feature of the proposed approach compared to previous synthetic aperture radar (SAR) tomography approaches is that it allows for an approximation-free height-dependent calculation of the sample covariance matrix by exploiting the azimuth-focused data on the 3-D reconstruction grid. The method is applied to experimental multibaseline quad-pol SAR data at L- and P-bands acquired by German Aerospace Center's (DLR) E-SAR sensor: Tomographic images of a partially forested area, including a 3-D voxel plot that visualizes the very high level of detail of the tomographic image, are shown, and an analysis of the focusing performance is given for the full as well as reduced synthetic aperture in the normal direction.

    @Article{freyMeier2010:TGARS,
    author = {Othmar Frey and Erich Meier},
    title = {{3-D} Time-Domain {SAR} Imaging of a Forest Using Airborne Multibaseline Data at {L}- and {P}-Bands},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2011},
    volume = {49},
    number = {10},
    pages = {3660-3664},
    month = oct,
    abstract = {In this paper, a time-domain back-projection based tomographic processing approach to a 3-D reconstruction grid is detailed, with the focusing in the third dimension being either modified versions of multilook standard beamforming, robust Capon beamforming, or multiple signal classification. The novel feature of the proposed approach compared to previous synthetic aperture radar (SAR) tomography approaches is that it allows for an approximation-free height-dependent calculation of the sample covariance matrix by exploiting the azimuth-focused data on the 3-D reconstruction grid. The method is applied to experimental multibaseline quad-pol SAR data at L- and P-bands acquired by German Aerospace Center's (DLR) E-SAR sensor: Tomographic images of a partially forested area, including a 3-D voxel plot that visualizes the very high level of detail of the tomographic image, are shown, and an analysis of the focusing performance is given for the full as well as reduced synthetic aperture in the normal direction.},
    doi = {10.1109/TGRS.2011.2128875},
    file = {:freyMeierTomoProcessing2011.pdf:PDF},
    keywords = {Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, synthetic aperture radar, SAR, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyMeierTomoProcessing2011.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5756480},
    
    }
    


  15. Othmar Frey and Erich Meier. Analyzing Tomographic SAR Data of a Forest With Respect to Frequency, Polarization, and Focusing Technique. IEEE Trans. Geosci. Remote Sens., 49(10):3648-3659, October 2011. Keyword(s): Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, synthetic aperture radar, SAR, scattering, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation.
    Abstract: Forest canopies are semitransparent to microwaves at both L- and P-bands. Thus, a number of scattering sources and different types of scattering mechanisms may contribute to a single range cell of a synthetic aperture radar (SAR) image. By appropriately combining the SAR data of multiple parallel flight paths, a large 2-D aperture is synthesized, which allows for tomographic imaging of the 3-D structure of such semitransparent media and the underlying ground. A separate paper deals with the actual tomographic imaging part that leads to the 3-D data cube. In particular, three focusing techniques are described and analyzed: multilook beamforming, robust Capon beamforming, and multiple signal classification beamforming. In this paper, the resulting data products obtained by tomographically focusing two airborne multibaseline SAR data sets of a partially forested area, one at L-band and another at P-band, are subject to a detailed analysis with respect to the location and the type of backscattering sources. In particular, the following aspects are investigated: 1) The forest structure, as obtained from the vertical profiles of intensities at sample plot locations within the forest, is compared to the height distribution of the top of the forest canopy, as derived from airborne laser scanning data, and profiles are presented for all polarimetric channels and focusing techniques, as well as at both frequencies; 2) the type and location of scattering mechanisms are analyzed as functions of height for the two frequencies, namely, L- and P-bands, and using the polarimetric channels, as well as the Pauli and Cloude-Pottier decompositions thereof; and 3) the accuracy of the ground elevation estimation obtained from the different focusing techniques and the two frequencies is assessed with the help of a lidar-derived digital elevation model.

    @Article{freyMeier2010DataAnalysis:TGARS,
    author = {Othmar Frey and Erich Meier},
    title = {Analyzing Tomographic {SAR} Data of a Forest With Respect to Frequency, Polarization, and Focusing Technique},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    year = {2011},
    volume = {49},
    number = {10},
    pages = {3648-3659},
    month = oct,
    abstract = {Forest canopies are semitransparent to microwaves at both L- and P-bands. Thus, a number of scattering sources and different types of scattering mechanisms may contribute to a single range cell of a synthetic aperture radar (SAR) image. By appropriately combining the SAR data of multiple parallel flight paths, a large 2-D aperture is synthesized, which allows for tomographic imaging of the 3-D structure of such semitransparent media and the underlying ground. A separate paper deals with the actual tomographic imaging part that leads to the 3-D data cube. In particular, three focusing techniques are described and analyzed: multilook beamforming, robust Capon beamforming, and multiple signal classification beamforming. In this paper, the resulting data products obtained by tomographically focusing two airborne multibaseline SAR data sets of a partially forested area, one at L-band and another at P-band, are subject to a detailed analysis with respect to the location and the type of backscattering sources. In particular, the following aspects are investigated: 1) The forest structure, as obtained from the vertical profiles of intensities at sample plot locations within the forest, is compared to the height distribution of the top of the forest canopy, as derived from airborne laser scanning data, and profiles are presented for all polarimetric channels and focusing techniques, as well as at both frequencies; 2) the type and location of scattering mechanisms are analyzed as functions of height for the two frequencies, namely, L- and P-bands, and using the polarimetric channels, as well as the Pauli and Cloude-Pottier decompositions thereof; and 3) the accuracy of the ground elevation estimation obtained from the different focusing techniques and the two frequencies is assessed with the help of a lidar-derived digital elevation model.},
    doi = {10.1109/TGRS.2011.2125972},
    file = {:freyMeierTomoAnalysis2011.pdf:PDF},
    keywords = {Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, synthetic aperture radar, SAR, scattering, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyMeierTomoAnalysis2011.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5751670},
    
    }
    


  16. Guido Gatti, Stefano Tebaldini, Mauro Mariotti d'Alessandro, and Fabio Rocca. ALGAE: A Fast Algebraic Estimation of Interferogram Phase Offsets in Space-Varying Geometries. IEEE Trans. Geosci. Remote Sens., 49(6):2343-2353, June 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, ALGAE, DLR, E-SAR airborne system, ESA BIOSAR 2008 campaign, European Space Agency, Experimental SAR airborne system, German Aerospace Center, P-band data set, airborne multipass interferometric campaigns, data stack phase locking, incidence angle sensitivity, interferogram phase offset algebraic estimation, interferogram phase offset compensation, multipass InSAR analysis, null space component identification, space varying geometries, synthetic aperture radar interferometry, system geometry space varying nature, system geometry variation, terrain topography estimation, terrain topography retrieval, geophysical signal processing, linear algebra, radar interferometry, radar signal processing, remote sensing by radar, synthetic aperture radar, terrain mapping, topography (Earth);.
    Abstract: This paper deals with the estimation of terrain topography from multipass synthetic aperture radar (SAR) interferometry (InSAR), focusing on the case where variation of the system geometry within the imaged swath is relevant. A typical case is represented by airborne multipass interferometric campaigns where, due to the closeness between the radar sensor and the targets, the incidence-angle sensitivity undergoes a dramatic increase with respect to the spaceborne case, resulting in a high spatial variability of the normal baselines. The space-varying nature of the system geometry gives rise to a major issue in multipass InSAR analyses in that it prevents from compensating for the presence of interferogram phase offsets by simply phase locking the data stack to a reference point, therefore hindering the retrieval of terrain topography. To cope with this issue properly, we propose a novel approach that exploits the algebraic properties of the problem. Such an approach allows casting the problem in terms of identification of a null-space component for terrain topography after which both topography and the interferogram phase offsets are quickly obtained without exploiting calibration points. Experimental results are shown based on a P-band data set acquired by the Experimental SAR (E-SAR) airborne system, operated by the German Aerospace Center (DLR), in the framework of the European Space Agency (ESA) campaign BIOSAR 2008.

    @Article{gattiTebaldiniMariottidAlessandroRocca2010ALGAE,
    Title = {ALGAE: A Fast Algebraic Estimation of Interferogram Phase Offsets in Space-Varying Geometries},
    Author = {Gatti, Guido and Tebaldini, Stefano and Mariotti d'Alessandro, Mauro and Rocca, Fabio},
    Doi = {10.1109/TGRS.2010.2091278},
    ISSN = {0196-2892},
    Month = jun,
    Number = {6},
    Pages = {2343-2353},
    Volume = {49},
    Year = {2011},
    Abstract = {This paper deals with the estimation of terrain topography from multipass synthetic aperture radar (SAR) interferometry (InSAR), focusing on the case where variation of the system geometry within the imaged swath is relevant. A typical case is represented by airborne multipass interferometric campaigns where, due to the closeness between the radar sensor and the targets, the incidence-angle sensitivity undergoes a dramatic increase with respect to the spaceborne case, resulting in a high spatial variability of the normal baselines. The space-varying nature of the system geometry gives rise to a major issue in multipass InSAR analyses in that it prevents from compensating for the presence of interferogram phase offsets by simply phase locking the data stack to a reference point, therefore hindering the retrieval of terrain topography. To cope with this issue properly, we propose a novel approach that exploits the algebraic properties of the problem. Such an approach allows casting the problem in terms of identification of a null-space component for terrain topography after which both topography and the interferogram phase offsets are quickly obtained without exploiting calibration points. Experimental results are shown based on a P-band data set acquired by the Experimental SAR (E-SAR) airborne system, operated by the German Aerospace Center (DLR), in the framework of the European Space Agency (ESA) campaign BIOSAR 2008.},
    Journal = {IEEE Trans. Geosci. Remote Sens.},
    Keywords = {SAR Processing, SAR Tomography, Tomography, ALGAE;DLR;E-SAR airborne system;ESA BIOSAR 2008 campaign;European Space Agency;Experimental SAR airborne system;German Aerospace Center;P-band data set;airborne multipass interferometric campaigns;data stack phase locking;incidence angle sensitivity;interferogram phase offset algebraic estimation;interferogram phase offset compensation;multipass InSAR analysis;null space component identification;space varying geometries;synthetic aperture radar interferometry;system geometry space varying nature;system geometry variation;terrain topography estimation;terrain topography retrieval;geophysical signal processing;linear algebra;radar interferometry;radar signal processing;remote sensing by radar;synthetic aperture radar;terrain mapping;topography (Earth);} 
    }
    


  17. K. Goel and N. Adam. Three-Dimensional Positioning of Point Scatterers Based on Radargrammetry. IEEE Trans. Geosci. Remote Sens., PP(99):1-9, 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography.
    Abstract: This paper presents a new technique for the retrieval of 3-D point scatterer (PS) location and resolution cell configuration exploiting only the intensity of synthetic aperture radar (SAR) images. The implemented method is based on the principle of radargrammetry and makes use of Bayesian inference, wherein, directed graphs are utilized to represent dependencies of random variables and probability density functions are modeled by particle filter representations. Compared to published radargrammetric work, the newly developed algorithm optimally exploits stacks of acquisitions taken with at least three different incidence angles. Due to the large angular diversity, the method is insensitive to atmospheric propagation effects and motion of the scatterers in contrast to the coherent phase-based techniques such as persistent scatterer interferometry and SAR Tomography. Additionally, the method estimates absolute height, which is a big advantage compared to the relative estimates provided by the phase-based techniques, which moreover encounter phase unwrapping errors and temporal decorrelation. High-resolution spotlight TerraSAR-X data of Berlin central station is used as a processing example for this technique. The test case demonstrates the unambiguous absolute height estimation of PSs and resolving of complicated scattering situations (e.g., layover) in urban areas.

    @Article{6087374,
    author = {Goel, K. and Adam, N.},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Three-Dimensional Positioning of Point Scatterers Based on Radargrammetry},
    year = {2011},
    issn = {0196-2892},
    number = {99},
    pages = {1-9},
    volume = {PP},
    abstract = {This paper presents a new technique for the retrieval of 3-D point scatterer (PS) location and resolution cell configuration exploiting only the intensity of synthetic aperture radar (SAR) images. The implemented method is based on the principle of radargrammetry and makes use of Bayesian inference, wherein, directed graphs are utilized to represent dependencies of random variables and probability density functions are modeled by particle filter representations. Compared to published radargrammetric work, the newly developed algorithm optimally exploits stacks of acquisitions taken with at least three different incidence angles. Due to the large angular diversity, the method is insensitive to atmospheric propagation effects and motion of the scatterers in contrast to the coherent phase-based techniques such as persistent scatterer interferometry and SAR Tomography. Additionally, the method estimates absolute height, which is a big advantage compared to the relative estimates provided by the phase-based techniques, which moreover encounter phase unwrapping errors and temporal decorrelation. High-resolution spotlight TerraSAR-X data of Berlin central station is used as a processing example for this technique. The test case demonstrates the unambiguous absolute height estimation of PSs and resolving of complicated scattering situations (e.g., layover) in urban areas.},
    doi = {10.1109/TGRS.2011.2171975},
    keywords = {SAR Processing, SAR Tomography, Tomography},
    
    }
    


  18. Roy E. Hansen, H. J. Callow, T. O. Sabo, and S. A. V. Synnes. Challenges in Seafloor Imaging and Mapping With Synthetic Aperture Sonar. IEEE Transactions on Geoscience and Remote Sensing, 49(10):3677-3687, October 2011. Keyword(s): Synthetic Aperture Sonar, SAS, bathymetry, oceanographic equipment, radar imaging, radar interferometry, seafloor phenomena, synthetic aperture sonar, underwater sound, HISAS 1030 interferometric SAS, acoustic signals, aided inertial navigation, bathymetry, centimeter resolution, coherence, grating lobes, image focusing, nonstraight tracks, ocean environment, real aperture interferometry, sea surface, seafloor imaging, seafloor mapping, shallow waters, sonar positioning, sound velocity, synthetic aperture sonar, vehicle instability, Apertures, Image resolution, Imaging, Sonar navigation, Synthetic aperture sonar, Vehicles, Interferometry, multiple reflections, navigation, nonlinear tracks, seafloor imaging, sound velocity errors, synthetic aperture radar (SAR), synthetic aperture sonar (SAS), topography errors.
    Abstract: Synthetic aperture sonar (SAS) is emerging as an imaging technology that can provide centimeter resolution over hundreds-of-meter range on the seafloor. Although the principle of SAS has been known for more than 30 years, SAS systems have only recently become commercially available. The success of SAS is critically dependent on overcoming several challenges related to the ocean environment. The sonar has to be positioned with accuracy better than a fraction of a wavelength along the synthetic aperture. We use the sensor itself for navigation, in combination with aided inertial navigation. The sound velocity has to be accurately estimated for successful focusing of SAS images. We calculate a simple rule of thumb for tolerance and show the effect of incorrect sound velocity. For nonstraight synthetic apertures, the bathymetry must be estimated. We use real aperture interferometry to map the scene before SAS processing. We calculate the required bathymetry accuracy and show the effects of insufficient mapping. Vehicle instability and nonstraight tracks, in combination with insufficient navigation accuracy, can cause grating lobes in the SAS images, which is not common in single-channel synthetic aperture radars. We show example imagery with severe grating lobes. In shallow waters, the acoustic signals will interact with the sea surface, possibly causing multipath. This will reduce the SAS quality. We use coherence to map the signal to multipath and, thereby, the valid sensor range. This paper illustrates the different challenges using examples from the HISAS 1030 interferometric SAS.

    @Article{hansenCallowSaboSynnesTGRS2011ChallengesInSeafloorImaginingWithSASonar,
    author = {Roy E. Hansen and H. J. Callow and T. O. Sabo and S. A. V. Synnes},
    title = {Challenges in Seafloor Imaging and Mapping With Synthetic Aperture Sonar},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    year = {2011},
    volume = {49},
    number = {10},
    pages = {3677-3687},
    month = {Oct},
    issn = {0196-2892},
    abstract = {Synthetic aperture sonar (SAS) is emerging as an imaging technology that can provide centimeter resolution over hundreds-of-meter range on the seafloor. Although the principle of SAS has been known for more than 30 years, SAS systems have only recently become commercially available. The success of SAS is critically dependent on overcoming several challenges related to the ocean environment. The sonar has to be positioned with accuracy better than a fraction of a wavelength along the synthetic aperture. We use the sensor itself for navigation, in combination with aided inertial navigation. The sound velocity has to be accurately estimated for successful focusing of SAS images. We calculate a simple rule of thumb for tolerance and show the effect of incorrect sound velocity. For nonstraight synthetic apertures, the bathymetry must be estimated. We use real aperture interferometry to map the scene before SAS processing. We calculate the required bathymetry accuracy and show the effects of insufficient mapping. Vehicle instability and nonstraight tracks, in combination with insufficient navigation accuracy, can cause grating lobes in the SAS images, which is not common in single-channel synthetic aperture radars. We show example imagery with severe grating lobes. In shallow waters, the acoustic signals will interact with the sea surface, possibly causing multipath. This will reduce the SAS quality. We use coherence to map the signal to multipath and, thereby, the valid sensor range. This paper illustrates the different challenges using examples from the HISAS 1030 interferometric SAS.},
    doi = {10.1109/TGRS.2011.2155071},
    file = {:hansenCallowSaboSynnesTGRS2011ChallengesInSeafloorImaginingWithSASonar.pdf:PDF},
    keywords = {Synthetic Aperture Sonar, SAS,bathymetry;oceanographic equipment;radar imaging;radar interferometry;seafloor phenomena;synthetic aperture sonar;underwater sound;HISAS 1030 interferometric SAS;acoustic signals;aided inertial navigation;bathymetry;centimeter resolution;coherence;grating lobes;image focusing;nonstraight tracks;ocean environment;real aperture interferometry;sea surface;seafloor imaging;seafloor mapping;shallow waters;sonar positioning;sound velocity;synthetic aperture sonar;vehicle instability;Apertures;Image resolution;Imaging;Sonar navigation;Synthetic aperture sonar;Vehicles;Interferometry;multiple reflections;navigation;nonlinear tracks;seafloor imaging;sound velocity errors;synthetic aperture radar (SAR);synthetic aperture sonar (SAS);topography errors},
    
    }
    


  19. Lorenzo Iannini and Andrea Monti Guarnieri. Atmospheric Phase Screen in Ground-Based Radar: Statistics and Compensation. IEEE Geoscience and Remote Sensing Letters, 8(3):537-541, May 2011. Keyword(s): atmospheric electromagnetic wave propagation, atmospheric humidity, atmospheric pressure, atmospheric techniques, atmospheric temperature, radiowave propagation, remote sensing by radar, APS removal, Bolzano, Italy, atmospheric humidity, atmospheric phase screen evaluation, atmospheric phase screen removal, atmospheric pressure, atmospheric temperature, compensation approach, ground based radar, initial calibration step, meteorological parameters, time varying delay statistics, Atmospheric modeling, Calibration, Coherence, Delay, Humidity, Radar, Refractive index, Atmospheric artifact compensation, differential interferometry, ground-based radar (GB-RADAR).
    Abstract: In this letter, we face one of the main issues in ground-based radar applications, i.e., the evaluation and removal of the atmospheric phase screen (APS). The time-varying delay statistics are assessed by means of both radars and meteo simulated data sets and are critically interpreted with particular reference to the entailed compensation issues. A compensation approach based on the available on-site meteo parameters (pressure, temperature, and humidity) is then investigated. The technique proposes an initial calibration step on humidity which leads to significant improvements in the APS removal. The results of the technique are discussed in the case of a real campaign data set (Bolzano, Italy) that covers a temporal baseline of about one week.

    @Article{ianniniMontiGuarnieriGRSL2011AtmosphereStatisticsGBSAR,
    author = {Lorenzo Iannini and Monti Guarnieri, Andrea},
    title = {Atmospheric Phase Screen in Ground-Based Radar: Statistics and Compensation},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    year = {2011},
    volume = {8},
    number = {3},
    pages = {537-541},
    month = may,
    issn = {1545-598X},
    abstract = {In this letter, we face one of the main issues in ground-based radar applications, i.e., the evaluation and removal of the atmospheric phase screen (APS). The time-varying delay statistics are assessed by means of both radars and meteo simulated data sets and are critically interpreted with particular reference to the entailed compensation issues. A compensation approach based on the available on-site meteo parameters (pressure, temperature, and humidity) is then investigated. The technique proposes an initial calibration step on humidity which leads to significant improvements in the APS removal. The results of the technique are discussed in the case of a real campaign data set (Bolzano, Italy) that covers a temporal baseline of about one week.},
    doi = {10.1109/LGRS.2010.2090647},
    file = {:ianniniMontiGuarnieriGRSL2011AtmosphereStatisticsGBSAR.pdf:PDF},
    keywords = {atmospheric electromagnetic wave propagation;atmospheric humidity;atmospheric pressure;atmospheric techniques;atmospheric temperature;radiowave propagation;remote sensing by radar;APS removal;Bolzano;Italy;atmospheric humidity;atmospheric phase screen evaluation;atmospheric phase screen removal;atmospheric pressure;atmospheric temperature;compensation approach;ground based radar;initial calibration step;meteorological parameters;time varying delay statistics;Atmospheric modeling;Calibration;Coherence;Delay;Humidity;Radar;Refractive index;Atmospheric artifact compensation;differential interferometry;ground-based radar (GB-RADAR)},
    owner = {ofrey},
    pdf = {../../../docs/ianniniMontiGuarnieriGRSL2011AtmosphereStatisticsGBSAR.pdf},
    
    }
    


  20. Tom R. Lauknes, Howard A. Zebker, and Y. Larsen. InSAR Deformation Time Series Using an L1-Norm Small-Baseline Approach. IEEE Trans. Geosci. Remote Sens., 49(1):536-546, January 2011. Keyword(s): SAR Processing, InSAR deformation time series, L1-norm small-baseline approach, displacement phase, land displacement monitoring, reweighted least squares algorithm, satellite data, satellite synthetic aperture radar interferometry, sparse data set, surface displacement, two-dimensional unwrapping, unwrapped interferogram, least squares approximations, radar interferometry, spaceborne radar, synthetic aperture radar, time series;.
    Abstract: Satellite synthetic aperture radar interferometry (InSAR) is an invaluable tool for land displacement monitoring. Improved access to time series of satellite data has led to the development of several innovative multitemporal algorithms. Small baseline (SB) is one such time-series InSAR method, based on combining and inverting a set of unwrapped interferograms for surface displacement. Two-dimensional unwrapping of sparse data sets is a challenging task, and unwrapping errors can lead to incorrectly estimated deformation time series. It is well known that L1-norm is more robust than L2-norm cost function minimization if the data set has a large number of outlying points. In this paper, we present an L1-norm-based SB method using an iteratively reweighted least squares algorithm. We show that the displacement phase of both synthetic data, as well as a real data set that covers the San Francisco Bay area, is recovered more accurately than with L2-norm solutions.

    @Article{lauknesZebkerLarsen2011,
    author = {Lauknes, Tom R. and Zebker, Howard A. and Larsen, Y.},
    title = {{InSAR} Deformation Time Series Using an {L1}-Norm Small-Baseline Approach},
    journal = {{IEEE} Trans. Geosci. Remote Sens.},
    year = {2011},
    volume = {49},
    number = {1},
    pages = {536-546},
    month = jan,
    issn = {0196-2892},
    abstract = {Satellite synthetic aperture radar interferometry (InSAR) is an invaluable tool for land displacement monitoring. Improved access to time series of satellite data has led to the development of several innovative multitemporal algorithms. Small baseline (SB) is one such time-series InSAR method, based on combining and inverting a set of unwrapped interferograms for surface displacement. Two-dimensional unwrapping of sparse data sets is a challenging task, and unwrapping errors can lead to incorrectly estimated deformation time series. It is well known that L1-norm is more robust than L2-norm cost function minimization if the data set has a large number of outlying points. In this paper, we present an L1-norm-based SB method using an iteratively reweighted least squares algorithm. We show that the displacement phase of both synthetic data, as well as a real data set that covers the San Francisco Bay area, is recovered more accurately than with L2-norm solutions.},
    doi = {10.1109/TGRS.2010.2051951},
    file = {:lauknesZebkerLarsen2011.pdf:PDF},
    keywords = {SAR Processing, InSAR deformation time series;L1-norm small-baseline approach;displacement phase;land displacement monitoring;reweighted least squares algorithm;satellite data;satellite synthetic aperture radar interferometry;sparse data set;surface displacement;two-dimensional unwrapping;unwrapped interferogram;least squares approximations;radar interferometry;spaceborne radar;synthetic aperture radar;time series;},
    owner = {ofrey},
    pdf = {../../../docs/lauknesZebkerLarsen2011.pdf},
    
    }
    


  21. Yun Lin, Wen Hong, Weixian Tan, Yanping Wang, and Yirong Wu. Interferometric Circular SAR Method for Three-Dimensional Imaging. IEEE Geosci. Remote Sens. Lett., 8(6):1026-1030, November 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, circular apertures, coherence, interferometric CSAR method, phase cycle ambiguities, phase difference, three dimensional imaging, tomographic imaging capability, coherence, radar imaging, remote sensing by radar, synthetic aperture radar;.
    Abstract: The aperture of 360 #x00B0; gives circular synthetic aperture radar (SAR) (CSAR) the capability to detect hidden target when its orientation is unknown. Subwavelength resolution can also be achieved when the target in the spotted area is observed under a complete circular aperture. Furthermore, the aspect angle diversity inherent to the circular trajectory makes possible a 3-D target reconstruction. However, the latter two potentials require certain target reflectivity homogeneity. For a highly directive scatterer, it has no resolving ability in the direction normal to the data collection plane. In this letter, a new interferometric CSAR method is presented to enhance the tomographic imaging capability for highly directive scatterers without sacrificing other scatterers' resolutions. This method takes advantage of the coherence and the phase difference between a pair of 3-D SAR images formed from data collected at two separate circular apertures to eliminate targets that focused at a wrong elevation. In addition, it uses two different transmit frequencies to solve the problem of phase cycle ambiguities. Finally, simulation results validate this new approach.

    @Article{5875868,
    Title = {Interferometric Circular SAR Method for Three-Dimensional Imaging},
    Author = {Yun Lin and Wen Hong and Weixian Tan and Yanping Wang and Yirong Wu},
    Doi = {10.1109/LGRS.2011.2150732},
    ISSN = {1545-598X},
    Month = nov,
    Number = {6},
    Pages = {1026-1030},
    Volume = {8},
    Year = {2011},
    Abstract = {The aperture of 360 #x00B0; gives circular synthetic aperture radar (SAR) (CSAR) the capability to detect hidden target when its orientation is unknown. Subwavelength resolution can also be achieved when the target in the spotted area is observed under a complete circular aperture. Furthermore, the aspect angle diversity inherent to the circular trajectory makes possible a 3-D target reconstruction. However, the latter two potentials require certain target reflectivity homogeneity. For a highly directive scatterer, it has no resolving ability in the direction normal to the data collection plane. In this letter, a new interferometric CSAR method is presented to enhance the tomographic imaging capability for highly directive scatterers without sacrificing other scatterers' resolutions. This method takes advantage of the coherence and the phase difference between a pair of 3-D SAR images formed from data collected at two separate circular apertures to eliminate targets that focused at a wrong elevation. In addition, it uses two different transmit frequencies to solve the problem of phase cycle ambiguities. Finally, simulation results validate this new approach.},
    Journal = {IEEE Geosci. Remote Sens. Lett.},
    Keywords = {SAR Processing, SAR Tomography, Tomography, circular apertures;coherence;interferometric CSAR method;phase cycle ambiguities;phase difference;three dimensional imaging;tomographic imaging capability;coherence;radar imaging;remote sensing by radar;synthetic aperture radar;} 
    }
    


  22. Yun Lin, Wen Hong, Weixian Tan, Yanping Wang, and Yirong Wu. Interferometric Circular SAR Method for Three-Dimensional Imaging. IEEE Geosci. Remote Sens. Lett., 8(6):1026-1030, November 2011. Keyword(s): circular apertures, coherence, interferometric CSAR method, phase cycle ambiguities, phase difference, three dimensional imaging, tomographic imaging capability, coherence, radar imaging, remote sensing by radar, synthetic aperture radar;.
    Abstract: The aperture of 360 #x00B0; gives circular synthetic aperture radar (SAR) (CSAR) the capability to detect hidden target when its orientation is unknown. Subwavelength resolution can also be achieved when the target in the spotted area is observed under a complete circular aperture. Furthermore, the aspect angle diversity inherent to the circular trajectory makes possible a 3-D target reconstruction. However, the latter two potentials require certain target reflectivity homogeneity. For a highly directive scatterer, it has no resolving ability in the direction normal to the data collection plane. In this letter, a new interferometric CSAR method is presented to enhance the tomographic imaging capability for highly directive scatterers without sacrificing other scatterers' resolutions. This method takes advantage of the coherence and the phase difference between a pair of 3-D SAR images formed from data collected at two separate circular apertures to eliminate targets that focused at a wrong elevation. In addition, it uses two different transmit frequencies to solve the problem of phase cycle ambiguities. Finally, simulation results validate this new approach.

    @Article{linHongTanWangWu2011,
    Title = {Interferometric Circular {SAR} Method for Three-Dimensional Imaging},
    Author = {Yun Lin and Wen Hong and Weixian Tan and Yanping Wang and Yirong Wu},
    Doi = {10.1109/LGRS.2011.2150732},
    ISSN = {1545-598X},
    Month = nov,
    Number = {6},
    Pages = {1026-1030},
    Volume = {8},
    Year = {2011},
    Abstract = {The aperture of 360 #x00B0; gives circular synthetic aperture radar (SAR) (CSAR) the capability to detect hidden target when its orientation is unknown. Subwavelength resolution can also be achieved when the target in the spotted area is observed under a complete circular aperture. Furthermore, the aspect angle diversity inherent to the circular trajectory makes possible a 3-D target reconstruction. However, the latter two potentials require certain target reflectivity homogeneity. For a highly directive scatterer, it has no resolving ability in the direction normal to the data collection plane. In this letter, a new interferometric CSAR method is presented to enhance the tomographic imaging capability for highly directive scatterers without sacrificing other scatterers' resolutions. This method takes advantage of the coherence and the phase difference between a pair of 3-D SAR images formed from data collected at two separate circular apertures to eliminate targets that focused at a wrong elevation. In addition, it uses two different transmit frequencies to solve the problem of phase cycle ambiguities. Finally, simulation results validate this new approach.},
    Journal = {IEEE Geosci. Remote Sens. Lett.},
    Keywords = {circular apertures;coherence;interferometric CSAR method;phase cycle ambiguities;phase difference;three dimensional imaging;tomographic imaging capability;coherence;radar imaging;remote sensing by radar;synthetic aperture radar;} 
    }
    


  23. Guoxiang Liu, Hongguo Jia, Rui Zhang, Huixin Zhang, Hongliang Jia, Bing Yu, and Mingzhi Sang. Exploration of Subsidence Estimation by Persistent Scatterer InSAR on Time Series of High Resolution TerraSAR-X Images. Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of, 4(1):159 -170, march 2011. Keyword(s): China, Jinghai County, Jinghu high-speed railway, Tianjin, X-band radar sensor, buildings, data reduction procedures, engineering risk assessment, ground subsidence, groundwater, high resolution TerraSAR-X images, in situ data, land use planning, manhole covers, persistent scatterer InSAR, radar line-of-sight direction, street lamps, subsidence estimation, time series, wavelength 3.1 cm, geomorphology, geophysical techniques, radar interferometry, remote sensing by radar, synthetic aperture radar;.
    Abstract: Ground subsidence is a major concern for land use planning and engineering risk assessment. This paper explores subsidence detection by the persistent scatterer (PS) interferometric synthetic aperture radar (InSAR) technique using the multitemporal high resolution spaceborne SAR images. We first describe the mathematical models and the data reduction procedures of the PS solution. The experiments of subsidence detection are then carried out over the Jinghai County in Tianjin (China) which has been sinking due to overuse of groundwater. The time series of high resolution SAR images collected by the X-band radar sensor onboard the satellite TerraSAR-X (TSX) are utilized for the PS detection, PS networking and subsidence estimation. The experimental results demonstrate that the high resolution of TSX SAR images can dramatically increase the PSs' density and coverage extent, especially in the built-up areas. Subsidence values can be extracted on the individual objects like buildings, street lamps and manhole covers, and on the linear engineering structures like the Jinghu high-speed railway. The PS InSAR with short radar wavelength (3.1 cm) is quite sensitive to ground displacement in the radar line-of-sight direction, and the derived subsidence measurements are in good agreement with the in situ data taken by optical leveling.

    @Article{5560692,
    author = {Guoxiang Liu and Hongguo Jia and Rui Zhang and Huixin Zhang and Hongliang Jia and Bing Yu and Mingzhi Sang},
    journal = {Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of},
    title = {Exploration of Subsidence Estimation by Persistent Scatterer InSAR on Time Series of High Resolution TerraSAR-X Images},
    year = {2011},
    issn = {1939-1404},
    month = {march},
    number = {1},
    pages = {159 -170},
    volume = {4},
    abstract = {Ground subsidence is a major concern for land use planning and engineering risk assessment. This paper explores subsidence detection by the persistent scatterer (PS) interferometric synthetic aperture radar (InSAR) technique using the multitemporal high resolution spaceborne SAR images. We first describe the mathematical models and the data reduction procedures of the PS solution. The experiments of subsidence detection are then carried out over the Jinghai County in Tianjin (China) which has been sinking due to overuse of groundwater. The time series of high resolution SAR images collected by the X-band radar sensor onboard the satellite TerraSAR-X (TSX) are utilized for the PS detection, PS networking and subsidence estimation. The experimental results demonstrate that the high resolution of TSX SAR images can dramatically increase the PSs' density and coverage extent, especially in the built-up areas. Subsidence values can be extracted on the individual objects like buildings, street lamps and manhole covers, and on the linear engineering structures like the Jinghu high-speed railway. The PS InSAR with short radar wavelength (3.1 cm) is quite sensitive to ground displacement in the radar line-of-sight direction, and the derived subsidence measurements are in good agreement with the in situ data taken by optical leveling.},
    doi = {10.1109/JSTARS.2010.2067446},
    keywords = {China;Jinghai County;Jinghu high-speed railway;Tianjin;X-band radar sensor;buildings;data reduction procedures;engineering risk assessment;ground subsidence;groundwater;high resolution TerraSAR-X images;in situ data;land use planning;manhole covers;persistent scatterer InSAR;radar line-of-sight direction;street lamps;subsidence estimation;time series;wavelength 3.1 cm;geomorphology;geophysical techniques;radar interferometry;remote sensing by radar;synthetic aperture radar;},
    
    }
    


  24. Paco López-Dekker, Pau Prats, F. De Zan, D. Schulze, G. Krieger, and Alberto Moreira. TanDEM-X First DEM Acquisition: A Crossing Orbit Experiment. IEEE Geoscience and Remote Sensing Letters, PP(99):1-943, 2011. Keyword(s): SAR Processing, InSAR, Interferometry, SAR Interferometry, TerrSAR-X, TanDEM-X, Spaceborne SAR, Single-Pass.
    Abstract: This letter describes the first interferometric acquisitions and results obtained by the TerraSAR-X add-on for Digital Elevation Measurements mission. Due to the large along-track separation between the two satellites during the approaching maneuver and the Earth's rotation, useful interferometric acquisitions were only possible at high latitudes. This resulted in a crossing angle between the ground tracks whose impact was corrected by acquiring the two synthetic-aperture radar images with an opposite squint. The still very large 2-km cross-track baseline resulted in a 3.8-m interferometric height of ambiguity, producing extremely detailed images of the topography of the target area. Results acquired over the October Revolution Island, Russia, are shown and discussed.

    @Article{lopezDekkerPratsDeZanSchulzeKriegerMoreira2011:TanDEM,
    author = {L\'opez-Dekker, Paco and Prats, Pau and De Zan, F. and Schulze, D. and Krieger, G. and Moreira, Alberto},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    title = {{TanDEM-X} First {DEM} Acquisition: A Crossing Orbit Experiment},
    year = {2011},
    issn = {1545-598X},
    number = {99},
    pages = {1-943},
    volume = {PP},
    abstract = {This letter describes the first interferometric acquisitions and results obtained by the TerraSAR-X add-on for Digital Elevation Measurements mission. Due to the large along-track separation between the two satellites during the approaching maneuver and the Earth's rotation, useful interferometric acquisitions were only possible at high latitudes. This resulted in a crossing angle between the ground tracks whose impact was corrected by acquiring the two synthetic-aperture radar images with an opposite squint. The still very large 2-km cross-track baseline resulted in a 3.8-m interferometric height of ambiguity, producing extremely detailed images of the topography of the target area. Results acquired over the October Revolution Island, Russia, are shown and discussed.},
    doi = {10.1109/LGRS.2011.2127444},
    keywords = {SAR Processing, InSAR, Interferometry, SAR Interferometry, TerrSAR-X, TanDEM-X, Spaceborne SAR, Single-Pass},
    owner = {ofrey},
    pdf = {../../../docs/lopezDekkerPratsDeZanSchulzeKriegerMoreira2011.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5773078},
    
    }
    


  25. O. Monserrat, Michele Crosetto, M. Cuevas, and B. Crippa. The Thermal Expansion Component of Persistent Scatterer Interferometry Observations. IEEE Geosci. Remote Sens. Lett., 8(5):864 -868, September 2011. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, Barcelona metropolitan area, PSI analysis, PSI products, Spain, TerraSAR-X spaceborne sensor, X-band SAR interferometric phases, deformation velocity maps, imaged objects, persistent scatterer interferometry observations, spaceborne radar, standard two-parameter PSI model, synthetic aperture radar acquisitions, thermal dilation parameter, thermal dilation phase component, thermal expansion component, thermal map, very high resolution X-band StripMap SAR data, geophysical image processing, geophysical techniques, radar interferometry, spaceborne radar, synthetic aperture radar, thermal expansion;.
    Abstract: This letter focuses on the thermal expansion component of persistent scatterer (PS) interferometry (PSI), which is a result of temperature differences in the imaged area between synthetic aperture radar (SAR) acquisitions. This letter is based on very high resolution X-band StripMap SAR data captured by the TerraSAR-X spaceborne sensor. The X-band SAR interferometric phases are highly influenced by the thermal dilation of the imaged objects. This phenomenon can have a strong impact on the PSI products, particularly on the deformation velocity maps, if not properly handled during the PSI analysis. In this letter, we propose a strategy to deal with the thermal dilation phase component, which involves further developing the standard two-parameter PSI model (deformation velocity and residual topographic error) with a third unknown parameter called the thermal dilation parameter, which is estimated for each PS. The map obtained from plotting this parameter for all PSs of a given area is hereafter called thermal map. This letter describes the proposed model and outlines the issue of parameter estimability. In addition, the potential of exploiting the thermal maps is analyzed by illustrating two examples of the Barcelona (Spain) metropolitan area. Thermal maps provide two types of information: The first one is the coefficient of thermal expansion of the observed objects, while the second one, which is related to the pattern of the thermal dilation parameter, gives information about the static structure of these objects. Two important aspects that influence the exploitation of thermal maps are discussed in the last section of this letter: the line-of-sight nature of the derived estimates and the achievable precision in the estimation of the coefficient of thermal expansion.

    @Article{monserratCrosettoCuevasCrippa2011PSI,
    Title = {The Thermal Expansion Component of Persistent Scatterer Interferometry Observations},
    Author = {Monserrat, O. and Crosetto, Michele and Cuevas, M. and Crippa, B.},
    Doi = {10.1109/LGRS.2011.2119463},
    ISSN = {1545-598X},
    Month = sep,
    Number = {5},
    Pages = {864 -868},
    Volume = {8},
    Year = {2011},
    Abstract = {This letter focuses on the thermal expansion component of persistent scatterer (PS) interferometry (PSI), which is a result of temperature differences in the imaged area between synthetic aperture radar (SAR) acquisitions. This letter is based on very high resolution X-band StripMap SAR data captured by the TerraSAR-X spaceborne sensor. The X-band SAR interferometric phases are highly influenced by the thermal dilation of the imaged objects. This phenomenon can have a strong impact on the PSI products, particularly on the deformation velocity maps, if not properly handled during the PSI analysis. In this letter, we propose a strategy to deal with the thermal dilation phase component, which involves further developing the standard two-parameter PSI model (deformation velocity and residual topographic error) with a third unknown parameter called the thermal dilation parameter, which is estimated for each PS. The map obtained from plotting this parameter for all PSs of a given area is hereafter called thermal map. This letter describes the proposed model and outlines the issue of parameter estimability. In addition, the potential of exploiting the thermal maps is analyzed by illustrating two examples of the Barcelona (Spain) metropolitan area. Thermal maps provide two types of information: The first one is the coefficient of thermal expansion of the observed objects, while the second one, which is related to the pattern of the thermal dilation parameter, gives information about the static structure of these objects. Two important aspects that influence the exploitation of thermal maps are discussed in the last section of this letter: the line-of-sight nature of the derived estimates and the achievable precision in the estimation of the coefficient of thermal expansion.},
    Journal = {IEEE Geosci. Remote Sens. Lett.},
    Keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI, Barcelona metropolitan area;PSI analysis;PSI products;Spain;TerraSAR-X spaceborne sensor;X-band SAR interferometric phases;deformation velocity maps;imaged objects;persistent scatterer interferometry observations;spaceborne radar;standard two-parameter PSI model;synthetic aperture radar acquisitions;thermal dilation parameter;thermal dilation phase component;thermal expansion component;thermal map;very high resolution X-band StripMap SAR data;geophysical image processing;geophysical techniques;radar interferometry;spaceborne radar;synthetic aperture radar;thermal expansion;} 
    }
    


  26. Daniele Perissin and Teng Wang. Time-Series InSAR Applications Over Urban Areas in China. Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of, 4(1):92-100, March 2011. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, SAR Interferometry, InSAR, DInSAR, Interferometry, geomorphology, radar interferometry, remote sensing by radar, synthetic aperture radar, terrain mapping, time series, Badong, Dragon project, European Space Agency, NRSCC, National Remote Sensing Center of China, PS-InSAR, Permanent Scatterers, Quasi-PS InSAR, SAR interferometry, Shanghai, Three Gorges Dam, Tianjin, big man-made structures, cities growth, coherent-uncoherent analysis, landslide monitoring, subsidence monitoring, terrain movement, time-series InSAR, urban areas, urban development, Synthetic aperture radar interferometry (InSAR), Three Gorges Project (TGP), time-series analysis, urban development;.
    Abstract: In this study, we present the results achieved within the Dragon project, a cooperation program between the European Space Agency (ESA) and the National Remote Sensing Center of China (NRSCC), about monitoring subsidences and landslides in urban areas, analyzing cities growth and measuring the deformation of big man-made structures. Among the processed areas, we report here the main results we obtained in the test sites of Shanghai, Tianjin, Badong, and Three Gorges Dam. The techniques that have been used to process the data are original SAR interferometry (InSAR), Permanent Scatterers (PS-InSAR), Quasi-PS InSAR (QPS-InSAR), and a combination of coherent-uncoherent analysis. The results show that time-series InSAR techniques allow us to extract ground information with high spatial density and thus help us understanding the impact of urban development on terrain movements.

    @Article{perissinWangJSTARS2011,
    author = {Perissin, Daniele and Teng Wang},
    title = {Time-Series {InSAR} Applications Over Urban Areas in {China}},
    journal = {Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of},
    year = {2011},
    volume = {4},
    number = {1},
    pages = {92-100},
    month = mar,
    issn = {1939-1404},
    abstract = {In this study, we present the results achieved within the Dragon project, a cooperation program between the European Space Agency (ESA) and the National Remote Sensing Center of China (NRSCC), about monitoring subsidences and landslides in urban areas, analyzing cities growth and measuring the deformation of big man-made structures. Among the processed areas, we report here the main results we obtained in the test sites of Shanghai, Tianjin, Badong, and Three Gorges Dam. The techniques that have been used to process the data are original SAR interferometry (InSAR), Permanent Scatterers (PS-InSAR), Quasi-PS InSAR (QPS-InSAR), and a combination of coherent-uncoherent analysis. The results show that time-series InSAR techniques allow us to extract ground information with high spatial density and thus help us understanding the impact of urban development on terrain movements.},
    doi = {10.1109/JSTARS.2010.2046883},
    file = {:perissinWangJSTARS2011.pdf:PDF},
    keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI, SAR Interferometry, InSAR, DInSAR, Interferometry, geomorphology;radar interferometry;remote sensing by radar;synthetic aperture radar;terrain mapping;time series;Badong;Dragon project;European Space Agency;NRSCC;National Remote Sensing Center of China;PS-InSAR;Permanent Scatterers;Quasi-PS InSAR;SAR interferometry;Shanghai;Three Gorges Dam;Tianjin;big man-made structures;cities growth;coherent-uncoherent analysis;landslide monitoring;subsidence monitoring;terrain movement;time-series InSAR;urban areas;urban development;Synthetic aperture radar interferometry (InSAR);Three Gorges Project (TGP);time-series analysis;urban development;},
    pdf = {../../../docs/perissinWangJSTARS2011.pdf},
    
    }
    


  27. Diego Reale, Gianfranco Fornaro, A. Pauciullo, Xiao Xiang Zhu, and Richard Bamler. Tomographic Imaging and Monitoring of Buildings With Very High Resolution SAR Data. IEEE Geosci. Remote Sens. Lett., 8(4):661-665, July 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, InSAR, SAR Interferometry, Interferometry, DInSAR, persistent scatterer interferometry, PSI, 3-D structure, 4-D imaging, TerraSAR-X spotlight acquisitions, buildings, high-resolution sensors, impressive reconstruction, medium-resolution SAR data tomographic techniques, scatterer density, steep topography, synthetic aperture radar, tomographic imaging, urban environment, geophysical image processing, image reconstruction, image resolution, radar resolution, remote sensing by radar, synthetic aperture radar.
    Abstract: Layover is frequent in imaging and monitoring with synthetic aperture radar (SAR) areas characterized by a high density of scatterers with steep topography, e.g., in urban environment. Using medium-resolution SAR data tomographic techniques has been proven to be capable of separating multiple scatterers interfering (in layover) in the same pixel. With the advent of the new generation of high-resolution sensors, the layover effect on buildings becomes more evident. In this letter, we exploit the potential of the 4-D imaging applied to a set of TerraSAR-X spotlight acquisitions. Results show that the combination of high-resolution data and advanced coherent processing techniques can lead to impressive reconstruction and monitoring capabilities of the whole 3-D structure of buildings.

    @Article{realeFornaroPauciulloZhuBamler2011,
    author = {Reale, Diego and Fornaro, Gianfranco and Pauciullo, A. and Zhu, Xiao Xiang and Bamler, Richard},
    title = {Tomographic Imaging and Monitoring of Buildings With Very High Resolution {SAR} Data},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2011},
    volume = {8},
    number = {4},
    pages = {661-665},
    month = jul,
    issn = {1545-598X},
    abstract = {Layover is frequent in imaging and monitoring with synthetic aperture radar (SAR) areas characterized by a high density of scatterers with steep topography, e.g., in urban environment. Using medium-resolution SAR data tomographic techniques has been proven to be capable of separating multiple scatterers interfering (in layover) in the same pixel. With the advent of the new generation of high-resolution sensors, the layover effect on buildings becomes more evident. In this letter, we exploit the potential of the 4-D imaging applied to a set of TerraSAR-X spotlight acquisitions. Results show that the combination of high-resolution data and advanced coherent processing techniques can lead to impressive reconstruction and monitoring capabilities of the whole 3-D structure of buildings.},
    doi = {10.1109/LGRS.2010.2098845},
    file = {:realeFornaroPauciulloZhuBamler2011.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Tomography, InSAR, SAR Interferometry, Interferometry, DInSAR, persistent scatterer interferometry, PSI, 3-D structure;4-D imaging;TerraSAR-X spotlight acquisitions;buildings;high-resolution sensors;impressive reconstruction;medium-resolution SAR data tomographic techniques;scatterer density;steep topography;synthetic aperture radar;tomographic imaging;urban environment;geophysical image processing;image reconstruction;image resolution;radar resolution;remote sensing by radar;synthetic aperture radar},
    owner = {ofrey},
    pdf = {../../../docs/realeFornaroPauciulloZhuBamler2011.pdf},
    
    }
    


  28. D. Reale, D. O. Nitti, D. Peduto, R. Nutricato, F. Bovenga, and G. Fornaro. Postseismic Deformation Monitoring With the COSMO/SKYMED Constellation. IEEE Geoscience and Remote Sensing Letters, PP(99):696-700, 2011. Keyword(s): SAR Processing, DInSAR, Deformation monitoring, InSAR, SAR Interferometry.
    Abstract: COSMO/SKYMED is currently the unique constellation of synthetic aperture radar (SAR) sensors operative, which is also for civilian use. On April 6, 2009, an Mw 6.3 earthquake struck the city of l'Aquila in Central Italy. The constellation acquired data stacks over the hit area at an unprecedented temporal rate. In this letter, the results obtained by processing several data set via two independent multitemporal differential interferometric SAR techniques are presented to demonstrate the capability of this constellation in postseismic deformations monitoring.

    @Article{5710028,
    author = {Reale, D. and Nitti, D. O. and Peduto, D. and Nutricato, R. and Bovenga, F. and Fornaro, G.},
    journal = {IEEE Geoscience and Remote Sensing Letters},
    title = {Postseismic Deformation Monitoring With the COSMO/SKYMED Constellation},
    year = {2011},
    issn = {1545-598X},
    number = {99},
    pages = {696-700},
    volume = {PP},
    abstract = {COSMO/SKYMED is currently the unique constellation of synthetic aperture radar (SAR) sensors operative, which is also for civilian use. On April 6, 2009, an Mw 6.3 earthquake struck the city of l'Aquila in Central Italy. The constellation acquired data stacks over the hit area at an unprecedented temporal rate. In this letter, the results obtained by processing several data set via two independent multitemporal differential interferometric SAR techniques are presented to demonstrate the capability of this constellation in postseismic deformations monitoring.},
    doi = {10.1109/LGRS.2010.2100364},
    keywords = {SAR Processing, DInSAR, Deformation monitoring, InSAR, SAR Interferometry},
    
    }
    


  29. A. Refice, A. Belmonte, F. Bovenga, and G. Pasquariello. On the Use of Anisotropic Covariance Models in Estimating Atmospheric DInSAR Contributions. IEEE Geoscience and Remote Sensing Letters, 8(2):341-345, March 2011. Keyword(s): DInSAR techniques, anisotropic atmospheric signals, anisotropic covariance models, atmospheric phase delays, atmospheric phase estimation, atmospheric phase screen field, automated methods, computational cost, correlation function parameters, critical sampling conditions, differential interferometric synthetic aperture radar data, kriging reconstruction approaches, persistent scatterer interferometry, sampling density, sparse-grid point-target DInSAR applications, spatial structure, stochastic models, synthetic aperture radar interferograms, atmospheric techniques, radar interferometry, stochastic processes, synthetic aperture radar;.
    Abstract: Stochastic models are often used to describe the spatial structure of atmospheric phase delays in differential interferometric synthetic aperture radar (DInSAR) data. Synthetic aperture radar interferograms often exhibit anisotropic atmospheric signals. In view of this, the use of anisotropic models for atmospheric phase estimation is increasingly advocated. However, anisotropic models lead to increased computational complexity in estimating the correlation function parameters with respect to the isotropic case. Moreover, the performance is degraded when dealing with DInSAR techniques involving only a few sparse points usable for computations, as in the case of persistent scatterer interferometry applications, particularly when this estimation has to be done in an automated way on many interferograms. In the present work, we propose some observations about the actual advantage given by anisotropic modeling of atmospheric phase in the case of sparse-grid point-target DInSAR applications. Through analysis of simulated data, we observe that an improvement in the performances of kriging reconstruction approaches can be obtained only when sufficient sampling densities are available. In critical sampling conditions, automated methods with reasonable computational cost may improve their performance if external information on the atmospheric phase screen field is available.

    @Article{reficeBelmonteBovengaPasquariello2011,
    Title = {On the Use of Anisotropic Covariance Models in Estimating Atmospheric {DInSAR} Contributions},
    Author = {Refice, A. and Belmonte, A. and Bovenga, F. and Pasquariello, G.},
    Doi = {10.1109/LGRS.2010.2073440},
    ISSN = {1545-598X},
    Month = mar,
    Number = {2},
    Pages = {341-345},
    Volume = {8},
    Year = {2011},
    Abstract = {Stochastic models are often used to describe the spatial structure of atmospheric phase delays in differential interferometric synthetic aperture radar (DInSAR) data. Synthetic aperture radar interferograms often exhibit anisotropic atmospheric signals. In view of this, the use of anisotropic models for atmospheric phase estimation is increasingly advocated. However, anisotropic models lead to increased computational complexity in estimating the correlation function parameters with respect to the isotropic case. Moreover, the performance is degraded when dealing with DInSAR techniques involving only a few sparse points usable for computations, as in the case of persistent scatterer interferometry applications, particularly when this estimation has to be done in an automated way on many interferograms. In the present work, we propose some observations about the actual advantage given by anisotropic modeling of atmospheric phase in the case of sparse-grid point-target DInSAR applications. Through analysis of simulated data, we observe that an improvement in the performances of kriging reconstruction approaches can be obtained only when sufficient sampling densities are available. In critical sampling conditions, automated methods with reasonable computational cost may improve their performance if external information on the atmospheric phase screen field is available.},
    Journal = {IEEE Geoscience and Remote Sensing Letters},
    Keywords = {DInSAR techniques;anisotropic atmospheric signals;anisotropic covariance models;atmospheric phase delays;atmospheric phase estimation;atmospheric phase screen field;automated methods;computational cost;correlation function parameters;critical sampling conditions;differential interferometric synthetic aperture radar data;kriging reconstruction approaches;persistent scatterer interferometry;sampling density;sparse-grid point-target DInSAR applications;spatial structure;stochastic models;synthetic aperture radar interferograms;atmospheric techniques;radar interferometry;stochastic processes;synthetic aperture radar;} 
    }
    


  30. Xiaozhen Ren, Jiantao Sun, and Ruliang Yang. A New Three-Dimensional Imaging Algorithm for Airborne Forward-Looking SAR. IEEE Geosci. Remote Sens. Lett., 8(1):153-157, January 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, Fourier transform, airborne forward-looking SAR, along-track processing, echo signal, imaging geometry, multiplication operations, nonlinear frequency modulation scaling, point scatterers, synthetic aperture radar, three-dimensional imaging algorithm, Fourier transforms, airborne radar, modulation, radar imaging, synthetic aperture radar;.
    Abstract: In this letter, a new 3-D imaging algorithm is proposed for forward-looking synthetic aperture radar based on the imaging geometry and the characteristic of the echo signal. The key point of the proposed algorithm is the introduction of the nonlinear frequency modulation scaling in along-track processing to obtain accurate focusing. As the method needs only Fourier transform and multiplication operations, it is computationally efficient. Simulations with point scatterers are used to validate the method.

    @Article{5535115,
    Title = {A New Three-Dimensional Imaging Algorithm for Airborne Forward-Looking {SAR}},
    Author = {Xiaozhen Ren and Jiantao Sun and Ruliang Yang},
    Doi = {10.1109/LGRS.2010.2055035},
    ISSN = {1545-598X},
    Month = jan,
    Number = {1},
    Pages = {153-157},
    Volume = {8},
    Year = {2011},
    Abstract = {In this letter, a new 3-D imaging algorithm is proposed for forward-looking synthetic aperture radar based on the imaging geometry and the characteristic of the echo signal. The key point of the proposed algorithm is the introduction of the nonlinear frequency modulation scaling in along-track processing to obtain accurate focusing. As the method needs only Fourier transform and multiplication operations, it is computationally efficient. Simulations with point scatterers are used to validate the method.},
    Journal = {IEEE Geosci. Remote Sens. Lett.},
    Keywords = {SAR Processing, SAR Tomography, Tomography, Fourier transform;airborne forward-looking SAR;along-track processing;echo signal;imaging geometry;multiplication operations;nonlinear frequency modulation scaling;point scatterers;synthetic aperture radar;three-dimensional imaging algorithm;Fourier transforms;airborne radar;modulation;radar imaging;synthetic aperture radar;} 
    }
    


  31. Angel Ribalta. Time-Domain Reconstruction Algorithms for FMCW-SAR. IEEE Geosci. Remote Sens. Lett., 8(3):396-400, May 2011. Keyword(s): SAR Processing, Time-Domain Back-Projection, TDBP, frequency-modulated continuous-wave, Ka-band, SAR, airborne SAR, FMCW, COBRA, Fraunhofer, FGAN, X-Band, W-Band, 10 GHz, 35 GHz, 94 GH, 220 GHz, 4 GHz Bandwidth at 35 and 94 GHz, 8 GHz Bandwidth at 220 GHz.
    Abstract: In this letter, we develop time-domain reconstruction algorithms for frequency-modulated continuous wave synthetic aperture radar (FMCW-SAR). The algorithms considered here are the time-domain correlation algorithm, and two versions of the backprojection algorithm: the standard one based on the start-stop approximation, and a modified version that takes into account the movement of the sensor during the transmission of the pulse. Numerical simulations illustrate the performance of the algorithms, showing that the start-stop approximation may not be valid for FMCW-SAR, whereas the modified backprojection algorithm works very well here.

    @Article{ribaltaGRSL2011TDBPforFMCW,
    author = {Ribalta, Angel},
    title = {Time-Domain Reconstruction Algorithms for {FMCW}-{SAR}},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2011},
    volume = {8},
    number = {3},
    pages = {396-400},
    month = may,
    issn = {1545-598X},
    abstract = {In this letter, we develop time-domain reconstruction algorithms for frequency-modulated continuous wave synthetic aperture radar (FMCW-SAR). The algorithms considered here are the time-domain correlation algorithm, and two versions of the backprojection algorithm: the standard one based on the start-stop approximation, and a modified version that takes into account the movement of the sensor during the transmission of the pulse. Numerical simulations illustrate the performance of the algorithms, showing that the start-stop approximation may not be valid for FMCW-SAR, whereas the modified backprojection algorithm works very well here.},
    doi = {10.1109/LGRS.2010.2078486},
    file = {:ribaltaGRSL2011TDBPforFMCW.pdf:PDF},
    keywords = {SAR Processing, Time-Domain Back-Projection, TDBP, frequency-modulated continuous-wave, Ka-band, SAR, airborne SAR, FMCW, COBRA, Fraunhofer, FGAN, X-Band, W-Band, 10 GHz, 35 GHz, 94 GH, 220 GHz, 4 GHz Bandwidth at 35 and 94 GHz, 8 GHz Bandwidth at 220 GHz},
    pdf = {../../../docs/ribaltaGRSL2011TDBPforFMCW.pdf},
    
    }
    


  32. Eric J. Rignot, J. Mouginot, and Bernd Scheuchl. Ice Flow of the Antarctic Ice Sheet. Science, 333(6048):1427-1430, 2011.
    Abstract: We present a reference, comprehensive, high-resolution, digital mosaic of ice motion in Antarctica assembled from multiple satellite interferometric synthetic-aperture radar data acquired during the International Polar Year 2007 to 2009. The data reveal widespread, patterned, enhanced flow with tributary glaciers reaching hundreds to thousands of kilometers inland over the entire continent. This view of ice sheet motion emphasizes the importance of basal-slip-dominated tributary flow over deformation-dominated ice sheet flow, redefines our understanding of ice sheet dynamics, and has far-reaching implications for the reconstruction and prediction of ice sheet evolution.

    @Article{rignotMouginotScheuchlScience2011,
    author = {Rignot, Eric J. and Mouginot, J. and Scheuchl, Bernd},
    title = {Ice Flow of the Antarctic Ice Sheet},
    journal = {Science},
    year = {2011},
    volume = {333},
    number = {6048},
    pages = {1427-1430},
    abstract = {We present a reference, comprehensive, high-resolution, digital mosaic of ice motion in Antarctica assembled from multiple satellite interferometric synthetic-aperture radar data acquired during the International Polar Year 2007 to 2009. The data reveal widespread, patterned, enhanced flow with tributary glaciers reaching hundreds to thousands of kilometers inland over the entire continent. This view of ice sheet motion emphasizes the importance of basal-slip-dominated tributary flow over deformation-dominated ice sheet flow, redefines our understanding of ice sheet dynamics, and has far-reaching implications for the reconstruction and prediction of ice sheet evolution.},
    doi = {10.1126/science.1208336},
    eprint = {http://www.sciencemag.org/content/333/6048/1427.full.pdf},
    file = {:rignotMouginotScheuchlScience2011.pdf:PDF},
    pdf = {../../../docs/rignotMouginotScheuchlScience2011.pdf},
    url = {http://www.sciencemag.org/content/333/6048/1427.abstract},
    
    }
    


  33. Marc Rodriguez-Cassola, Pau Prats, Gerhard Krieger, and Alberto Moreira. Efficient Time-Domain Image Formation with Precise Topography Accommodation for General Bistatic SAR Configurations. IEEE Transactions on Aerospace and Electronic Systems, 47(4):2949-2966, October 2011. Keyword(s): SAR Processing, Bistatic SAR, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, Fast Back-Projection, Back-Projection, Doppler information, German Aerospace Center, TerraSAR-X/F-SAR bistatic data, TerraSAR-X, F-SAR, nonstationary bistatic acquisitions, phase-preserving bistatic focusing, synchronization algorithm, airborne radar, backscatter, calibration, data acquisition, geophysical signal processing, radar signal processing, remote sensing by radar, spaceborne radar, synchronisation, synthetic aperture radar.
    Abstract: Due to the lack of an appropriate symmetry in the acquisition geometry, general bistatic synthetic aperture radar (SAR) cannot benefit from the two main properties of low-to-moderate resolution monostatic SAR: azimuth-invariance and topography-insensitivity. The precise accommodation of azimuth-variance and topography is a real challenge for efficent image formation algorithms working in the Fourier domain, but can be quite naturally handled by time-domain approaches. We present an efficient and practical implementation of a generalised bistatic SAR image formation algorithm with an accurate accommodation of these two effects. The algorithm has a common structure with the monostatic fast-factorised backprojection (FFBP), and is therefore based on subaperture processing. The images computed over the different subapertures are displayed in an advantageous elliptical coordinate system capable of incorporating the topographic information of the imaged scene in an analogous manner as topography-dependent monostatic SAR algorithms do. Analytical expressions for the Nyquist requirements using this coordinate system are derived. The overall discussion includes practical implementation hints and a realistic computational burden estimation. The algorithm is tested with both simulated and actual bistatic SAR data. The actual data correspond to the spaceborne-airborne experiment between TerraSAR-X and F-SAR performed in 2007 and to the DLR-ONERA airborne experiment carried out in 2003. The presented approach proves its suitability for the precise SAR focussing of the data acquired in general bistatic configurations.

    @Article{rodriguezCassolaPratsKriegerMoreiraTAES2011,
    author = {Rodriguez-Cassola, Marc and Prats, Pau and Krieger, Gerhard and Moreira, Alberto},
    title = {Efficient Time-Domain Image Formation with Precise Topography Accommodation for General Bistatic {SAR} Configurations},
    journal = {IEEE Transactions on Aerospace and Electronic Systems},
    year = {2011},
    volume = {47},
    number = {4},
    pages = {2949-2966},
    month = oct,
    issn = {0018-9251},
    abstract = {Due to the lack of an appropriate symmetry in the acquisition geometry, general bistatic synthetic aperture radar (SAR) cannot benefit from the two main properties of low-to-moderate resolution monostatic SAR: azimuth-invariance and topography-insensitivity. The precise accommodation of azimuth-variance and topography is a real challenge for efficent image formation algorithms working in the Fourier domain, but can be quite naturally handled by time-domain approaches. We present an efficient and practical implementation of a generalised bistatic SAR image formation algorithm with an accurate accommodation of these two effects. The algorithm has a common structure with the monostatic fast-factorised backprojection (FFBP), and is therefore based on subaperture processing. The images computed over the different subapertures are displayed in an advantageous elliptical coordinate system capable of incorporating the topographic information of the imaged scene in an analogous manner as topography-dependent monostatic SAR algorithms do. Analytical expressions for the Nyquist requirements using this coordinate system are derived. The overall discussion includes practical implementation hints and a realistic computational burden estimation. The algorithm is tested with both simulated and actual bistatic SAR data. The actual data correspond to the spaceborne-airborne experiment between TerraSAR-X and F-SAR performed in 2007 and to the DLR-ONERA airborne experiment carried out in 2003. The presented approach proves its suitability for the precise SAR focussing of the data acquired in general bistatic configurations.},
    doi = {10.1109/TAES.2011.6034676},
    file = {:rodriguezCassolaPratsKriegerMoreiraTAES2011.pdf:PDF},
    keywords = {SAR Processing,Bistatic SAR, Time-Domain Back-Projection, TDBP, Fast-Factorized Back-Projection, FFBP, Fast Back-Projection, Back-Projection,Doppler information, German Aerospace Center, TerraSAR-X/F-SAR bistatic data,TerraSAR-X, F-SAR, nonstationary bistatic acquisitions, phase-preserving bistatic focusing, synchronization algorithm, airborne radar, backscatter, calibration, data acquisition, geophysical signal processing, radar signal processing, remote sensing by radar, spaceborne radar, synchronisation, synthetic aperture radar},
    owner = {ofrey},
    pdf = {../../../docs/rodriguezCassolaPratsKriegerMoreiraTAES2011.pdf},
    
    }
    


  34. S. Samsonov and K. Tiampo. Polarization Phase Difference Analysis for Selection of Persistent Scatterers in SAR Interferometry. IEEE Geoscience and Remote Sensing Letters, 8(2):331-335, March 2011. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, HH channel, SAR Interferometry, San Francisco region, VV channel, amplitude dispersion threshold, data acquisition, deformation map, normalized PPD, odd bounce scattering properties, polarization phase difference analysis, quadpol RADARSAT-2 SAR images, standard PSI technique, standard persistent scatterer interferometry, synthetic aperture radar images, geophysical image processing, geophysical techniques, radar interferometry, synthetic aperture radar;.
    Abstract: In this letter, we propose a technique for selecting persistent scatterers (PSs) based on their polarization phase difference (PPD). We analyze a normalized PPD between HH and VV channels averaged over a temporal set of images and select pixels that demonstrate predominantly even or odd bounce scattering properties. We compare selected scatterers to PSs selected by applying an amplitude dispersion threshold as suggested by a standard PS interferometry (PSI) approach and show that both methods are complementary. However, the proposed approach can be potentially used on a small set of synthetic aperture radar (SAR) images, which can be beneficial in the early stage of data acquisition. We apply the proposed technique to produce a deformation map for the San Francisco region from six quad-pol RADARSAT-2 SAR images acquired during 2008-2009. The coverage and the precision of the produced deformation map are higher than if it was calculated with the standard PSI technique applied to the same data set.

    @Article{samsonovTiampo2011,
    Title = {Polarization Phase Difference Analysis for Selection of Persistent Scatterers in SAR Interferometry},
    Author = {Samsonov, S. and Tiampo, K.},
    Doi = {10.1109/LGRS.2010.2072904},
    ISSN = {1545-598X},
    Month = mar,
    Number = {2},
    Pages = {331-335},
    Volume = {8},
    Year = {2011},
    Abstract = {In this letter, we propose a technique for selecting persistent scatterers (PSs) based on their polarization phase difference (PPD). We analyze a normalized PPD between HH and VV channels averaged over a temporal set of images and select pixels that demonstrate predominantly even or odd bounce scattering properties. We compare selected scatterers to PSs selected by applying an amplitude dispersion threshold as suggested by a standard PS interferometry (PSI) approach and show that both methods are complementary. However, the proposed approach can be potentially used on a small set of synthetic aperture radar (SAR) images, which can be beneficial in the early stage of data acquisition. We apply the proposed technique to produce a deformation map for the San Francisco region from six quad-pol RADARSAT-2 SAR images acquired during 2008-2009. The coverage and the precision of the produced deformation map are higher than if it was calculated with the standard PSI technique applied to the same data set.},
    Journal = {IEEE Geoscience and Remote Sensing Letters},
    Keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI, HH channel;SAR Interferometry;San Francisco region;VV channel;amplitude dispersion threshold;data acquisition;deformation map;normalized PPD;odd bounce scattering properties;polarization phase difference analysis;quadpol RADARSAT-2 SAR images;standard PSI technique;standard persistent scatterer interferometry;synthetic aperture radar images;geophysical image processing;geophysical techniques;radar interferometry;synthetic aperture radar;} 
    }
    


  35. Stefan Sauer, Laurent Ferro-Famil, Andreas Reigber, and Eric Pottier. Three-Dimensional Imaging and Scattering Mechanism Estimation Over Urban Scenes Using Dual-Baseline Polarimetric InSAR Observations at L-Band. IEEE Trans. Geosci. Remote Sens., PP(99):1-14, 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, Capon, MUSIC, multiple signal classification, Polarimetry, Multibaseline SAR, InSAR, Interferometry, SAR Interferometry, Urban Remote Sensing.
    Abstract: This paper introduces new polarimetric algorithms for generating 3-D images and estimating scattering mechanisms from polarimetric multibaseline (MB) interferometric synthetic aperture radar (SAR) measurements. First, an MB interferometric SAR signal model is generalized to the fully polarimetric configuration, establishing the notion of polarimetric reflectivity. Subsequently, polarimetric beamforming, Capon, and MUSIC methods that determine optimal polarization combinations for height estimation are developed. These new techniques allow for extracting the height of reflectors, the associated scattering mechanisms, and the polarimetric (pseudo)reflectivities. By means of polarimetric dual-baseline interferometric SAR observations of an urban environment, the performance of the conceived algorithms is examined in detail. Producing 3-D images of a building layover, the quality of the approaches is compared in terms of refined resolution and lowered side lobes. Furthermore, the scattering processes occurring in urban scenes are investigated thoroughly by analyzing the optimal reflection types. The algorithms are validated using dual-baseline polarimetric SAR interferometric data at L-band acquired by German Aerospace Center's experimental SAR system over Dresden city.

    @Article{sauerFerroFamilReigberPottier2011:TomoUrban,
    author = {Sauer, Stefan and Ferro-Famil, Laurent and Reigber, Andreas and Pottier, Eric},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Three-Dimensional Imaging and Scattering Mechanism Estimation Over Urban Scenes Using Dual-Baseline Polarimetric {InSAR} Observations at {L}-Band},
    year = {2011},
    issn = {0196-2892},
    number = {99},
    pages = {1-14},
    volume = {PP},
    abstract = {This paper introduces new polarimetric algorithms for generating 3-D images and estimating scattering mechanisms from polarimetric multibaseline (MB) interferometric synthetic aperture radar (SAR) measurements. First, an MB interferometric SAR signal model is generalized to the fully polarimetric configuration, establishing the notion of polarimetric reflectivity. Subsequently, polarimetric beamforming, Capon, and MUSIC methods that determine optimal polarization combinations for height estimation are developed. These new techniques allow for extracting the height of reflectors, the associated scattering mechanisms, and the polarimetric (pseudo)reflectivities. By means of polarimetric dual-baseline interferometric SAR observations of an urban environment, the performance of the conceived algorithms is examined in detail. Producing 3-D images of a building layover, the quality of the approaches is compared in terms of refined resolution and lowered side lobes. Furthermore, the scattering processes occurring in urban scenes are investigated thoroughly by analyzing the optimal reflection types. The algorithms are validated using dual-baseline polarimetric SAR interferometric data at L-band acquired by German Aerospace Center's experimental SAR system over Dresden city.},
    doi = {10.1109/TGRS.2011.2147321},
    keywords = {SAR Processing, SAR Tomography, Tomography, Capon, MUSIC, multiple signal classification, Polarimetry, Multibaseline SAR, InSAR, Interferometry, SAR Interferometry, Urban Remote Sensing},
    owner = {ofrey},
    pdf = {../../../docs/sauerFerroFamilReigberPottier2011.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5887412},
    
    }
    


  36. D.J. Sego, H. Griffiths, and M.C. Wicks. Waveform and aperture design for low-frequency RF tomography. IET Radar, Sonar Navigation, 5(6):686-696, July 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, RF spectral environment, aperture Fourier surface, frequency selection, high vertical resolution circular SAR, image quality metrics, image resolution, image sidelobe, low-frequency RF tomography, spectrally sparse narrowband waveforms, ultrawideband waveforms, image resolution, radar imaging, synthetic aperture radar, tomography;.
    Abstract: Multiple applications would benefit from low frequency, three-dimensional (3-D), high resolution, imagery, among them remote archeological survey through foliage, and detecting voids in collapsed structures and underground. High vertical resolution circular SAR requires ultrawideband waveforms, a problematic aspect in the modern RF spectral environment, particularly at lower frequencies. RF tomography offers the potential to yield high, 3-D resolution using spectrally sparse, narrowband waveforms simultaneously with operation at frequencies that have demonstrated favourable penetration through intervening dielectric media. In this paper, we explore this potential; evaluating minimal spatial support tomographic apertures, combining diverse narrowband signals with 2- and 3-dimensional monostatic and bistatic apertures. Results are presented in terms of image quality metrics: resolution and sidelobe levels. It is shown that, generally, frequency selection is a soft constraint in terms of the achievable resolution and sidelobe levels, that the tomographic aperture with spatial sampling that is linearly continuous and substantially less than hemispherical yields high spatial resolution, and that there is interaction between the tomographic aperture and the waveform set as evidenced in the point spread function. Additionally the bistatic contribution of the collection aperture Fourier surface is demonstrated to enhance image quality when combined in a hybrid monostatic-bistatic aperture.

    @Article{5940386,
    Title = {Waveform and aperture design for low-frequency RF tomography},
    Author = {Sego, D.J. and Griffiths, H. and Wicks, M.C.},
    Doi = {10.1049/iet-rsn.2011.0014},
    ISSN = {1751-8784},
    Month = jul,
    Number = {6},
    Pages = {686-696},
    Volume = {5},
    Year = {2011},
    Abstract = {Multiple applications would benefit from low frequency, three-dimensional (3-D), high resolution, imagery, among them remote archeological survey through foliage, and detecting voids in collapsed structures and underground. High vertical resolution circular SAR requires ultrawideband waveforms, a problematic aspect in the modern RF spectral environment, particularly at lower frequencies. RF tomography offers the potential to yield high, 3-D resolution using spectrally sparse, narrowband waveforms simultaneously with operation at frequencies that have demonstrated favourable penetration through intervening dielectric media. In this paper, we explore this potential; evaluating minimal spatial support tomographic apertures, combining diverse narrowband signals with 2- and 3-dimensional monostatic and bistatic apertures. Results are presented in terms of image quality metrics: resolution and sidelobe levels. It is shown that, generally, frequency selection is a soft constraint in terms of the achievable resolution and sidelobe levels, that the tomographic aperture with spatial sampling that is linearly continuous and substantially less than hemispherical yields high spatial resolution, and that there is interaction between the tomographic aperture and the waveform set as evidenced in the point spread function. Additionally the bistatic contribution of the collection aperture Fourier surface is demonstrated to enhance image quality when combined in a hybrid monostatic-bistatic aperture.},
    Journal = {IET Radar, Sonar Navigation},
    Keywords = {SAR Processing, SAR Tomography, Tomography,RF spectral environment;aperture Fourier surface;frequency selection;high vertical resolution circular SAR;image quality metrics;image resolution;image sidelobe;low-frequency RF tomography;spectrally sparse narrowband waveforms;ultrawideband waveforms;image resolution;radar imaging;synthetic aperture radar;tomography;} 
    }
    


  37. Piyush Shanker Agram, F. Casu, Howard A. Zebker, and R. Lanari. Comparison of Persistent Scatterers and Small Baseline Time-Series InSAR Results: A Case Study of the San Francisco Bay Area. IEEE Geosci. Remote Sens. Lett., 8(4):592-596, July 2011. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, Small Baseline Subset Algorithm, SBAS, Interferometry, InSAR, SAR Interferometry, Deformation, Deformation Monitoring.
    Abstract: Time-series interferometric synthetic aperture radar (InSAR) methods estimate the spatiotemporal evolution of deformation over large areas by incorporating information from multiple SAR interferograms. Persistent scatterer (PS) and small baseline (SB) methods, which identify areas where the surface is least affected by geometric and temporal decorrelation, represent two families of time-series InSAR techniques to study successfully a wide spectrum of ground deformation phenomena worldwide. However, little is known comparatively about the performance of PS and SB techniques applied to the same region. Here, we compare quantitatively and cross validate the time-series InSAR results generated using two representative algorithms -- the maximum likelihood PS method and the small baseline subset algorithm -- in selected test sites, over the San Francisco Bay Area imaged by European Remote Sensing (ERS) sensors during 1995-2000. We present line of sight (LOS) velocities and deformation time series using both techniques and show that the root mean squared differences of the estimated mean velocities and deformation from each method are about 1 mm/year and 5 mm, respectively. These values are within expected noise levels and a characteristic of the pixel selection parameters for both the time-series techniques. We validate our deformation estimates against creep measurements from alignment arrays along the Hayward Fault and show that our estimates agree to within 0.5 mm/year LOS velocity and 1.5 mm LOS displacement.

    @Article{shankerAgramCasuZebkerLanari2011:PSI_SBAS,
    Title = {Comparison of Persistent Scatterers and Small Baseline Time-Series {InSAR} Results: A Case Study of the {San Francisco} Bay Area},
    Author = {Shanker Agram, Piyush and Casu, F. and Zebker, Howard A. and Lanari, R.},
    Doi = {10.1109/LGRS.2010.2095829},
    ISSN = {1545-598X},
    Month = jul,
    Number = {4},
    Pages = {592-596},
    Volume = {8},
    Year = {2011},
    Abstract = {Time-series interferometric synthetic aperture radar (InSAR) methods estimate the spatiotemporal evolution of deformation over large areas by incorporating information from multiple SAR interferograms. Persistent scatterer (PS) and small baseline (SB) methods, which identify areas where the surface is least affected by geometric and temporal decorrelation, represent two families of time-series InSAR techniques to study successfully a wide spectrum of ground deformation phenomena worldwide. However, little is known comparatively about the performance of PS and SB techniques applied to the same region. Here, we compare quantitatively and cross validate the time-series InSAR results generated using two representative algorithms -- the maximum likelihood PS method and the small baseline subset algorithm -- in selected test sites, over the San Francisco Bay Area imaged by European Remote Sensing (ERS) sensors during 1995-2000. We present line of sight (LOS) velocities and deformation time series using both techniques and show that the root mean squared differences of the estimated mean velocities and deformation from each method are about 1 mm/year and 5 mm, respectively. These values are within expected noise levels and a characteristic of the pixel selection parameters for both the time-series techniques. We validate our deformation estimates against creep measurements from alignment arrays along the Hayward Fault and show that our estimates agree to within 0.5 mm/year LOS velocity and 1.5 mm LOS displacement.},
    Journal = {{IEEE} Geosci. Remote Sens. Lett.},
    Keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI, Small Baseline Subset Algorithm, SBAS, Interferometry, InSAR, SAR Interferometry, Deformation, Deformation Monitoring},
    Owner = {ofrey},
    Pdf = {../../../docs/shankerAgramCasuZebkerLanari2011.pdf} 
    }
    


  38. Manoochehr Shirzaei and Thomas R Walter. Estimating the effect of satellite orbital error using wavelet-based robust regression applied to InSAR deformation data. IEEE Transactions on Geoscience and Remote Sensing, 49(11):4600-4605, 2011.
    @Article{Shirzaei2011,
    author = {Shirzaei, Manoochehr and Walter, Thomas R},
    title = {Estimating the effect of satellite orbital error using wavelet-based robust regression applied to InSAR deformation data},
    year = {2011},
    volume = {49},
    number = {11},
    pages = {4600--4605},
    journal = {IEEE Transactions on Geoscience and Remote Sensing},
    owner = {ofrey},
    publisher = {IEEE},
    
    }
    


  39. Manoochehr Shirzaei, TR Walter, HR Nankali, and EP Holohan. Gravity-driven deformation of Damavand volcano, Iran, detected through InSAR time series. Geology, 39(3):251-254, 2011.
    @Article{Shirzaei2011a,
    author = {Shirzaei, Manoochehr and Walter, TR and Nankali, HR and Holohan, EP},
    title = {Gravity-driven deformation of Damavand volcano, Iran, detected through InSAR time series},
    year = {2011},
    volume = {39},
    number = {3},
    pages = {251--254},
    journal = {Geology},
    owner = {ofrey},
    publisher = {Geological Society of America},
    
    }
    


  40. David Small. Flattening Gamma: Radiometric Terrain Correction for SAR Imagery. IEEE Trans. Geosci. Remote Sens., 49(8):3081-3093, August 2011. Keyword(s): SAR Processing, ASAR, ERS-1, Earth ellipsoid model, Earth terrain-model, PALSAR, RADARSAT-1, SAR sensors, TerraSAR-X, beta nought SAR radiometry, elevation models, gamma nought SAR radiometry, image geolocation accuracy, radar cross section, radar imaging, radar measurements, radar scattering, radar terrain factors, radiometric calibration, radiometric normalisation standard, sigma nought SAR radiometry, terrain variations, radar cross-sections, radar imaging, radiometry, synthetic aperture radar, terrain mapping.
    Abstract: Enabling intercomparison of synthetic aperture radar (SAR) imagery acquired from different sensors or acquisition modes requires accurate modeling of not only the geometry of each scene, but also of systematic influences on the radiometry of individual scenes. Terrain variations affect not only the position of a given point on the earth's surface but also the brightness of the radar return as expressed in radar geometry. Without treatment, the hill-slope modulations of the radiometry threaten to overwhelm weaker thematic land cover induced backscatter differences, and comparison of backscatter from multiple satellites, modes, or tracks loses meaning. The ASAR and PALSAR sensors provide state vectors and timing with higher absolute accuracy than was previously available, allowing them to directly support accurate tie-point-free geolocation and radiometric normalization of their imagery. Given accurate knowledge of the acquisition geometry of a SAR image together with a digital height model (DHM) of the area imaged, radiometric image simulation is applied to estimate the local illuminated area for each point in the image. Ellipsoid-based or sigma naught $(sigma^{0})$ based incident angle approximations that fail to reproduce the effect of topographic variation in their sensor model are contrasted with a new method that integrates terrain variations with the concept of gamma naught $(gamma^{0})$ backscatter, converting directly from beta naught $(beta^{0})$ to a newly introduced terrain-flattened $gamma^{0}$ normalization convention. The interpretability of imagery treated in this manner is improved in comparison to processing based on conventional ellipsoid or local incident angle based $sigma^{0}$ normalization.

    @Article{small2011:TGRSRadiometricCalibration,
    Title = {Flattening Gamma: Radiometric Terrain Correction for {SAR} Imagery},
    Author = {Small, David},
    Doi = {10.1109/TGRS.2011.2120616},
    ISSN = {0196-2892},
    Month = aug,
    Number = {8},
    Pages = {3081-3093},
    Url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5752845},
    Volume = {49},
    Year = {2011},
    Abstract = {Enabling intercomparison of synthetic aperture radar (SAR) imagery acquired from different sensors or acquisition modes requires accurate modeling of not only the geometry of each scene, but also of systematic influences on the radiometry of individual scenes. Terrain variations affect not only the position of a given point on the earth's surface but also the brightness of the radar return as expressed in radar geometry. Without treatment, the hill-slope modulations of the radiometry threaten to overwhelm weaker thematic land cover induced backscatter differences, and comparison of backscatter from multiple satellites, modes, or tracks loses meaning. The ASAR and PALSAR sensors provide state vectors and timing with higher absolute accuracy than was previously available, allowing them to directly support accurate tie-point-free geolocation and radiometric normalization of their imagery. Given accurate knowledge of the acquisition geometry of a SAR image together with a digital height model (DHM) of the area imaged, radiometric image simulation is applied to estimate the local illuminated area for each point in the image. Ellipsoid-based or sigma naught $(sigma^{0})$ based incident angle approximations that fail to reproduce the effect of topographic variation in their sensor model are contrasted with a new method that integrates terrain variations with the concept of gamma naught $(gamma^{0})$ backscatter, converting directly from beta naught $(beta^{0})$ to a newly introduced terrain-flattened $gamma^{0}$ normalization convention. The interpretability of imagery treated in this manner is improved in comparison to processing based on conventional ellipsoid or local incident angle based $sigma^{0}$ normalization.},
    Journal = {IEEE Trans. Geosci. Remote Sens.},
    Keywords = {SAR Processing, ASAR;ERS-1;Earth ellipsoid model;Earth terrain-model;PALSAR;RADARSAT-1;SAR sensors;TerraSAR-X;beta nought SAR radiometry;elevation models;gamma nought SAR radiometry;image geolocation accuracy;radar cross section;radar imaging;radar measurements;radar scattering;radar terrain factors;radiometric calibration;radiometric normalisation standard;sigma nought SAR radiometry;terrain variations;radar cross-sections;radar imaging;radiometry;synthetic aperture radar;terrain mapping},
    Owner = {ofrey},
    Pdf = {../../../docs/small2011.pdf} 
    }
    


  41. Guangcai Sun, Mengdao Xing, Yong Wang, Yufeng Wu, YiRong Wu, and Zheng Bao. Sliding Spotlight and TOPS SAR Data Processing Without Subaperture. IEEE Geosci. Remote Sens. Lett., 8(6):1036-1040, November 2011. Keyword(s): SAR Processing, TOPS, Terrain Observation by Progressive Scans, data acquisition, synthetic aperture radar, Doppler domain, TOPS SAR data processing, azimuth bandwidth, azimuth signal aliasing, data acquisition, imaging algorithm, instantaneous bandwidth, progressive scan, pulse repetition frequency, sliding spotlight, subaperture method, synthetic aperture radar, terrain observation, Azimuth, Bandwidth, Chirp, Focusing, Signal processing algorithms, Synthetic aperture radar, Sliding spotlight synthetic aperture radar (SAR), subaperture, terrain observation by progressive scan (TOPS) SAR.
    Abstract: During the data acquisition of a sliding spotlight or terrain observation by progressive scan (TOPS) synthetic aperture radar (SAR), the steering of the antenna main beam increases the azimuth bandwidth but could result in the azimuth signal aliasing in the Doppler domain. To remove the aliasing, one has used a subaperture method. In this letter, we show a focusing scheme without the use of the subaperture for both sliding spotlight and TOPS SARs. In doing so, we eliminated the obvious increase in data volume or the subaperture division by choosing the pulse repetition frequency that is only 20% greater than the instantaneous bandwidth. The method was incorporated with an available imaging algorithm and then used to process simulated and collected data of the sliding spotlight and TOPS SARs. Well-focused results without aliasing were obtained.

    @Article{sunXingWangWuWuBaoGRSL2011TOPSwithoutSubaperture,
    author = {Guangcai Sun and Mengdao Xing and Yong Wang and Yufeng Wu and YiRong Wu and Zheng Bao},
    title = {Sliding Spotlight and {TOPS} {SAR} Data Processing Without Subaperture},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2011},
    volume = {8},
    number = {6},
    pages = {1036-1040},
    month = {Nov},
    issn = {1545-598X},
    abstract = {During the data acquisition of a sliding spotlight or terrain observation by progressive scan (TOPS) synthetic aperture radar (SAR), the steering of the antenna main beam increases the azimuth bandwidth but could result in the azimuth signal aliasing in the Doppler domain. To remove the aliasing, one has used a subaperture method. In this letter, we show a focusing scheme without the use of the subaperture for both sliding spotlight and TOPS SARs. In doing so, we eliminated the obvious increase in data volume or the subaperture division by choosing the pulse repetition frequency that is only 20% greater than the instantaneous bandwidth. The method was incorporated with an available imaging algorithm and then used to process simulated and collected data of the sliding spotlight and TOPS SARs. Well-focused results without aliasing were obtained.},
    doi = {10.1109/LGRS.2011.2151174},
    file = {:sunXingWangWuWuBaoGRSL2011TOPSwithoutSubaperture.pdf:PDF},
    keywords = {SAR Processing, TOPS, Terrain Observation by Progressive Scans,data acquisition;synthetic aperture radar;Doppler domain;TOPS SAR data processing;azimuth bandwidth;azimuth signal aliasing;data acquisition;imaging algorithm;instantaneous bandwidth;progressive scan;pulse repetition frequency;sliding spotlight;subaperture method;synthetic aperture radar;terrain observation;Azimuth;Bandwidth;Chirp;Focusing;Signal processing algorithms;Synthetic aperture radar;Sliding spotlight synthetic aperture radar (SAR);subaperture;terrain observation by progressive scan (TOPS) SAR},
    pdf = {../../../docs/sunXingWangWuWuBaoGRSL2011TOPSwithoutSubaperture.pdf},
    
    }
    


  42. Xiaoqing Wu, K.C. Jezek, E. Rodriguez, S. Gogineni, F. Rodriguez-Morales, and A. Freeman. Ice Sheet Bed Mapping With Airborne SAR Tomography. IEEE Trans. Geosci. Remote Sens., 49(10):3791 -3802, oct. 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, 2D image formation, 3D tomographic ice sounding method, AD 2006 05, AD 2008 07, airborne SAR tomography, ice sheet bed mapping, ice sheet surface topography, ice thickness, multiple-phase-center VHF radar system, nadir depth sounder tracks, swath measurements, time-domain subaperture method, very high frequency radar data, geophysical image processing, glaciology, hydrological techniques, radar imaging, remote sensing by radar, synthetic aperture radar;.
    Abstract: We develop and then demonstrate a 3-D tomographic ice sounding method applied to very high frequency (VHF) radar data that produces swath measurements of ice sheet surface topography, ice thickness, and radar reflectivity of both the surface and bed of the ice sheet. First, we formulate the ice sheet imaging problem as a problem of estimating signal arrival angles and illustrate how the method resolves ambiguous echoes arriving simultaneously from the left and right sides of the aircraft, as well as from the surface and base of the ice sheet. We then discuss why we chose the time-domain subaperture method for 2-D image formation for ice sounding. We apply the tomographic technique to the data that we collected in May 2006 and again in July 2008 from a multiple-phase-center VHF radar system. We present 3-D images of the upper and lower surfaces of the ice sheet and compare the estimated surface topography with Ice, Cloud, and land Elevation Satellite altimeter nadir track measurements and the measured swath ice thickness with independent nadir depth sounder tracks. We achieved a 5-m surface topography accuracy and a 14-m ice thickness accuracy.

    @Article{5766033,
    author = {Xiaoqing Wu and Jezek, K.C. and Rodriguez, E. and Gogineni, S. and Rodriguez-Morales, F. and Freeman, A.},
    journal = {IEEE Trans. Geosci. Remote Sens.},
    title = {Ice Sheet Bed Mapping With Airborne SAR Tomography},
    year = {2011},
    issn = {0196-2892},
    month = {oct.},
    number = {10},
    pages = {3791 -3802},
    volume = {49},
    abstract = {We develop and then demonstrate a 3-D tomographic ice sounding method applied to very high frequency (VHF) radar data that produces swath measurements of ice sheet surface topography, ice thickness, and radar reflectivity of both the surface and bed of the ice sheet. First, we formulate the ice sheet imaging problem as a problem of estimating signal arrival angles and illustrate how the method resolves ambiguous echoes arriving simultaneously from the left and right sides of the aircraft, as well as from the surface and base of the ice sheet. We then discuss why we chose the time-domain subaperture method for 2-D image formation for ice sounding. We apply the tomographic technique to the data that we collected in May 2006 and again in July 2008 from a multiple-phase-center VHF radar system. We present 3-D images of the upper and lower surfaces of the ice sheet and compare the estimated surface topography with Ice, Cloud, and land Elevation Satellite altimeter nadir track measurements and the measured swath ice thickness with independent nadir depth sounder tracks. We achieved a 5-m surface topography accuracy and a 14-m ice thickness accuracy.},
    doi = {10.1109/TGRS.2011.2132802},
    keywords = {SAR Processing, SAR Tomography, Tomography, 2D image formation;3D tomographic ice sounding method;AD 2006 05;AD 2008 07;airborne SAR tomography;ice sheet bed mapping;ice sheet surface topography;ice thickness;multiple-phase-center VHF radar system;nadir depth sounder tracks;swath measurements;time-domain subaperture method;very high frequency radar data;geophysical image processing;glaciology;hydrological techniques;radar imaging;remote sensing by radar;synthetic aperture radar;},
    
    }
    


  43. Wei Xu, Pingping Huang, Yunkai Deng, Jiantao Sun, and Xiuqin Shang. An Efficient Approach With Scaling Factors for TOPS-Mode SAR Data Focusing. IEEE Geosci. Remote Sens. Lett., 8(5):929-933, Sept 2011. 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 Terrain Observation by Progressive Scans (TOPS) mode is a novel spaceborne imaging mode which can be used to obtain wide-swath coverage and overcome major drawbacks in conventional ScanSAR. An efficient full-aperture imaging approach, which takes advantage of the two-step focusing technique and the azimuth baseband scaling operation, is presented for processing the TOPS-mode synthetic aperture radar (SAR) data. First, the proposed two-step focusing technique for spotlight and sliding spotlight SAR data focusing is adopted to resolve the aliased Doppler spectrum. Afterward, the following extended chirp scaling processing procedure with azimuth scaling factors is used to implement the residual TOPS raw-data focusing. Since the use of subapertures is avoided and only a limited azimuth-data extension is required, this algorithm is highly efficient. Simulation results validate the proposed imaging approach.

    @Article{xuHuangDengSunShangGRSL2011TOPS,
    author = {Wei Xu and Pingping Huang and Yunkai Deng and Jiantao Sun and Xiuqin Shang},
    title = {An Efficient Approach With Scaling Factors for {TOPS}-Mode {SAR} Data Focusing},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2011},
    volume = {8},
    number = {5},
    pages = {929-933},
    month = {Sept},
    issn = {1545-598X},
    abstract = {The Terrain Observation by Progressive Scans (TOPS) mode is a novel spaceborne imaging mode which can be used to obtain wide-swath coverage and overcome major drawbacks in conventional ScanSAR. An efficient full-aperture imaging approach, which takes advantage of the two-step focusing technique and the azimuth baseband scaling operation, is presented for processing the TOPS-mode synthetic aperture radar (SAR) data. First, the proposed two-step focusing technique for spotlight and sliding spotlight SAR data focusing is adopted to resolve the aliased Doppler spectrum. Afterward, the following extended chirp scaling processing procedure with azimuth scaling factors is used to implement the residual TOPS raw-data focusing. Since the use of subapertures is avoided and only a limited azimuth-data extension is required, this algorithm is highly efficient. Simulation results validate the proposed imaging approach.},
    doi = {10.1109/LGRS.2011.2135837},
    file = {:xuHuangDengSunShangGRSL2011TOPS.pdf:PDF},
    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/xuHuangDengSunShangGRSL2011TOPS.pdf},
    
    }
    


  44. Dochul Yang and Sean M. Buckley. Estimating High-Resolution Atmospheric Phase Screens From Radar Interferometry Data. IEEE Transactions on Geoscience and Remote Sensing, 49(8):3117 -3128, August 2011. Keyword(s): SAR Processing, Persistent Scatterer Interferometry, PSI, Arizona, HiRAPS algorithm, InSAR deformation measurement, Phoenix, Radarsat-1 image, USA, bubbles, deformation time series, height error difference, high-resolution atmospheric phase screen estimation, high-spatial-frequency atmospheric effects, multiinterferogram phase correlation, nonlinear deformation, persistent scatterer algorithm, pixel density, radar interferometry data, root mean square error, satellite-orbit repeat cycle, short-period interferogram, singular value decomposition, spatiotemporal filtering, time series algorithm, time-linear deformation, topographic phase contribution, geophysical image processing, geophysical techniques, mean square error methods, radar imaging, radar interferometry, remote sensing by radar, singular value decomposition, synthetic aperture radar, time series;.
    Abstract: Radar interferometry (InSAR) deformation measurements are afflicted by artifacts associated with the atmosphere and errors in removing the topographic phase contribution. We present a new time series algorithm that eliminates high-spatial-frequency atmospheric effects (bubbles) not removed with existing advanced InSAR approaches applied to measurements of smoothly varying deformation through time. Our High-Resolution Atmospheric Phase Screen (APS) (HiRAPS) algorithm initially uses a connected set of short-period interferograms, each spanning no more than three satellite-orbit repeat cycles. We estimate height error differences between a pixel and its neighbors within a radius chosen to be significantly smaller than a bubble. The height errors are unwrapped and removed from those pixels with high values of a newly defined multi-interferogram phase correlation. We then create a deformation time series for the pixels using singular value decomposition. The high-resolution APS are estimated from a dense set of pixels using spatiotemporal filtering. We evaluate the HiRAPS algorithm on simulated data consisting of realistic time-linear and nonlinear deformation, height errors, and bubbles. The root mean square error between all simulated and estimated APS pixels is 0.26 rad with the HiRAPS algorithm and 0.39 rad with a persistent scatterer (PS) algorithm. We also apply the HiRAPS algorithm to 66 Radarsat-1 images of Phoenix, AZ. Our HiRAPS approach results in an 18-fold increase in APS pixel density over PS processing. After removing the HiRAPS and PS APS from PS interferograms, we find that HiRAPS provides an 18 percent increase in the number of final PS detected.

    @Article{zangBuckley2011PSIAtmo,
    Title = {Estimating High-Resolution Atmospheric Phase Screens From Radar Interferometry Data},
    Author = {Dochul Yang and Buckley, Sean M.},
    Doi = {10.1109/TGRS.2011.2122338},
    ISSN = {0196-2892},
    Month = aug,
    Number = {8},
    Pages = {3117 -3128},
    Volume = {49},
    Year = {2011},
    Abstract = {Radar interferometry (InSAR) deformation measurements are afflicted by artifacts associated with the atmosphere and errors in removing the topographic phase contribution. We present a new time series algorithm that eliminates high-spatial-frequency atmospheric effects (bubbles) not removed with existing advanced InSAR approaches applied to measurements of smoothly varying deformation through time. Our High-Resolution Atmospheric Phase Screen (APS) (HiRAPS) algorithm initially uses a connected set of short-period interferograms, each spanning no more than three satellite-orbit repeat cycles. We estimate height error differences between a pixel and its neighbors within a radius chosen to be significantly smaller than a bubble. The height errors are unwrapped and removed from those pixels with high values of a newly defined multi-interferogram phase correlation. We then create a deformation time series for the pixels using singular value decomposition. The high-resolution APS are estimated from a dense set of pixels using spatiotemporal filtering. We evaluate the HiRAPS algorithm on simulated data consisting of realistic time-linear and nonlinear deformation, height errors, and bubbles. The root mean square error between all simulated and estimated APS pixels is 0.26 rad with the HiRAPS algorithm and 0.39 rad with a persistent scatterer (PS) algorithm. We also apply the HiRAPS algorithm to 66 Radarsat-1 images of Phoenix, AZ. Our HiRAPS approach results in an 18-fold increase in APS pixel density over PS processing. After removing the HiRAPS and PS APS from PS interferograms, we find that HiRAPS provides an 18 percent increase in the number of final PS detected.},
    Journal = {IEEE Transactions on Geoscience and Remote Sensing},
    Keywords = {SAR Processing, Persistent Scatterer Interferometry, PSI, Arizona;HiRAPS algorithm;InSAR deformation measurement;Phoenix;Radarsat-1 image;USA;bubbles;deformation time series;height error difference;high-resolution atmospheric phase screen estimation;high-spatial-frequency atmospheric effects;multiinterferogram phase correlation;nonlinear deformation;persistent scatterer algorithm;pixel density;radar interferometry data;root mean square error;satellite-orbit repeat cycle;short-period interferogram;singular value decomposition;spatiotemporal filtering;time series algorithm;time-linear deformation;topographic phase contribution;geophysical image processing;geophysical techniques;mean square error methods;radar imaging;radar interferometry;remote sensing by radar;singular value decomposition;synthetic aperture radar;time series;} 
    }
    


  45. Xiao Xiang Zhu and Richard Bamler. Let's Do the Time Warp: Multicomponent Nonlinear Motion Estimation in Differential SAR Tomography. IEEE Geosci. Remote Sens. Lett., 8(4):735-739, 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, Estimation, Persistent Scatterer Interferometry, PSI, Motion estimation, Pixel, Remote sensing, Signal to noise ratio, Synthetic aperture radar, Tomography, motion estimation, radar imaging, synthetic aperture radar, time warp simulation, tomography, D-TomoSAR system model, TerraSAR-X spotlight, complex motion model, differential synthetic aperture radar tomography, linear motion, motion history, multicomponent generalization, multicomponent nonlinear motion estimation, nonlinear motion, periodic motion component, spectral estimation, time warp method, user-defined motion model order, Differential synthetic aperture radar tomography (D-TomoSAR), TerraSAR-X (TS-X), multicomponent nonlinear motion, synthetic aperture radar (SAR), time warp;.
    Abstract: In the differential synthetic aperture radar tomography (D-TomoSAR) system model, the motion history appears as a phase term. In the case of nonlinear motion, this phase term is no longer linear and, hence, cannot be retrieved by spectral estimation. We propose the #x201C;time warp #x201D; method that rearranges the acquisition dates such that a linear motion is pretended. The multicomponent generalization of time warp rewrites the D-TomoSAR system model to an (M + 1)-dimensional standard spectral estimation problem, where M indicates the user-defined motion model order and, hence, enables the motion estimation for all possible complex motion models. Both simulations and real data (from TerraSAR-X spotlight) examples demonstrate the applicability of the method and show that linear and periodic (seasonal) motion components can be separated and retrieved.

    @Article{zhuBamlerGRSL2011,
    author = {Xiao Xiang Zhu and Richard Bamler},
    title = {Let's Do the Time Warp: Multicomponent Nonlinear Motion Estimation in Differential {SAR} Tomography},
    journal = {IEEE Geosci. Remote Sens. Lett.},
    year = {2011},
    volume = {8},
    number = {4},
    pages = {735-739},
    abstract = {In the differential synthetic aperture radar tomography (D-TomoSAR) system model, the motion history appears as a phase term. In the case of nonlinear motion, this phase term is no longer linear and, hence, cannot be retrieved by spectral estimation. We propose the #x201C;time warp #x201D; method that rearranges the acquisition dates such that a linear motion is pretended. The multicomponent generalization of time warp rewrites the D-TomoSAR system model to an (M + 1)-dimensional standard spectral estimation problem, where M indicates the user-defined motion model order and, hence, enables the motion estimation for all possible complex motion models. Both simulations and real data (from TerraSAR-X spotlight) examples demonstrate the applicability of the method and show that linear and periodic (seasonal) motion components can be separated and retrieved.},
    doi = {10.1109/LGRS.2010.2103298},
    file = {:zhuBamlerGRSL2011.pdf:PDF},
    keywords = {SAR Processing, SAR Tomography, Tomography, Estimation;Persistent Scatterer Interferometry, PSI,Motion estimation;Pixel;Remote sensing;Signal to noise ratio;Synthetic aperture radar;Tomography;motion estimation;radar imaging;synthetic aperture radar;time warp simulation;tomography;D-TomoSAR system model;TerraSAR-X spotlight;complex motion model;differential synthetic aperture radar tomography;linear motion;motion history;multicomponent generalization;multicomponent nonlinear motion estimation;nonlinear motion;periodic motion component;spectral estimation;time warp method;user-defined motion model order;Differential synthetic aperture radar tomography (D-TomoSAR);TerraSAR-X (TS-X);multicomponent nonlinear motion;synthetic aperture radar (SAR);time warp;},
    owner = {ofrey},
    pdf = {../../../docs/zhuBamlerGRSL2011.pdf},
    
    }
    


Conference articles

  1. J. Abril, E. Nova, A. Broquetas, A. Aguasca, J. Romeu, and L. Jofre. Deforming and relief interferometric SAR imaging at W-band. In 2011 International Conference on Infrared, Millimeter, and Terahertz Waves, pages 1-2, October 2011. Keyword(s): SAR Processing, W-Band, backpropagation, deformation, millimetre wave antennas, radar antennas, radar imaging, radar interferometry, receiving antennas, reflectivity, rough surfaces, synthetic aperture radar, L-shape target, W-band, backpropagation algorithm, image local deformation, interferogram coherence, interferometric phase difference, interferometric synthetic aperture radar, metallic rough surface deformation test, micrometric displacement, radar reflectivity, relief interferometric SAR imaging, scattered field, surface random change, surface relieve retrieval, Antenna measurements, Image resolution, Imaging, Radar imaging, Rough surfaces, Surface roughness, Surface topography.
    Abstract: Interferometry at W Band can be exploited to form images of small deformations with precisions in the order of tenths of microns and retrieve surface relieves. An Interferometric Synthetic Aperture Radar setup is proposed in which the scattered field is focused using a combination of range compression and backpropagation algorithm. Interferometric images involving micrometric displacements have been obtained showing a good agreement between real and measured displacements. A metallic rough surface deformation test has been first performed, by imaging the phase difference between acquisitions before and after the displacement. The interferometric phase difference between acquisitions can be used to image local deformations from a range of several meters. Furthermore the interferogram coherence shows the degree of decorrelation of the radar reflectivity which provides valuable information for surface random change. Likewise the relief of the surface with an L-shape target is retrieved mapping the phase difference between the two receiving antennas, in this case an static scenario is required.

    @INPROCEEDINGS{abrilNovaBroquetasAguascaRomeuJofre2011WBANDSARDeformationAndRelief,
    author={J. Abril and E. Nova and A. Broquetas and A. Aguasca and J. Romeu and L. Jofre},
    booktitle={2011 International Conference on Infrared, Millimeter, and Terahertz Waves},
    title={Deforming and relief interferometric SAR imaging at W-band},
    year={2011},
    volume={},
    number={},
    pages={1-2},
    abstract={Interferometry at W Band can be exploited to form images of small deformations with precisions in the order of tenths of microns and retrieve surface relieves. An Interferometric Synthetic Aperture Radar setup is proposed in which the scattered field is focused using a combination of range compression and backpropagation algorithm. Interferometric images involving micrometric displacements have been obtained showing a good agreement between real and measured displacements. A metallic rough surface deformation test has been first performed, by imaging the phase difference between acquisitions before and after the displacement. The interferometric phase difference between acquisitions can be used to image local deformations from a range of several meters. Furthermore the interferogram coherence shows the degree of decorrelation of the radar reflectivity which provides valuable information for surface random change. Likewise the relief of the surface with an L-shape target is retrieved mapping the phase difference between the two receiving antennas, in this case an static scenario is required.},
    keywords={SAR Processing, W-Band,backpropagation;deformation;millimetre wave antennas;radar antennas;radar imaging;radar interferometry;receiving antennas;reflectivity;rough surfaces;synthetic aperture radar;L-shape target;W-band;backpropagation algorithm;image local deformation;interferogram coherence;interferometric phase difference;interferometric synthetic aperture radar;metallic rough surface deformation test;micrometric displacement;radar reflectivity;relief interferometric SAR imaging;scattered field;surface random change;surface relieve retrieval;Antenna measurements;Image resolution;Imaging;Radar imaging;Rough surfaces;Surface roughness;Surface topography},
    doi={10.1109/irmmw-THz.2011.6104977},
    ISSN={2162-2027},
    month=oct,
    owner = {ofrey},
    
    }
    


  2. Esteban Aguilera, Matteo Nannini, and Andreas Reigber. Multi-signal compressed sensing for polarimetric SAR tomography. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 1369-1372, July 2011. Keyword(s): Airborne SAR, SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, Distributed Compressive Sensing, DCS methodology, E-SAR sensor, SAR image, azimuth-range pixel, distributed compressed sensing, elevation direction, fully polarimetric L-band data, multiplicative speckle noise, multisignal compressed sensing, pass acquisition geometry, polarimetric SAR tomography, polarimetric channel, space-borne radar platform, synthetic aperture radar, three dimensional imaging, tomographic focusing approach, tomographic signal, vertical reflectivity function, image reconstruction, image resolution, image sensors, radar imaging, radar polarimetry, radar resolution, spaceborne radar, speckle, synthetic aperture radar, tomography;.
    Abstract: In recent years, three-dimensional imaging by means of SAR tomography has become a field of intensive research. In SAR tomography, the vertical reflectivity function for every azimuth-range pixel is usually recovered by processing data collected using a defined repeat pass acquisition geometry. The most common approach is to generate a synthetic aperture in the elevation direction through imaging from a large number of parallel tracks. This imaging technique is appealing, since it is very simple. However, it has the draw back that large temporal baselines, which is the case for space-borne platforms, can severely affect the reconstruction. In an attempt to reduce the number of parallel tracks, we propose a new tomographic focusing approach that trades number of SAR images for correlations between neighboring azimuth-range pixels and polarimetric channels. As a matter of fact, this can be done under the framework of Distributed Compressed Sensing (DCS), which stems from Compressed Sensing (CS) theory, thus also exploiting sparsity in our tomographic signal. In addition, we address the problem of measurements affected by additive as well as multiplicative speckle noise. Results demonstrating the potential of the DCS methodology will be validated by using fully polarimetric L-band data acquired by the E-SAR sensor of DLR.

    @InProceedings{aguileraNanniniReigber2011,
    Title = {Multi-signal compressed sensing for polarimetric {SAR} tomography},
    Author = {Aguilera, Esteban and Nannini, Matteo and Reigber, Andreas},
    Booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    Doi = {10.1109/IGARSS.2011.6049320},
    Month = jul,
    Pages = {1369-1372},
    Year = {2011},
    Abstract = {In recent years, three-dimensional imaging by means of SAR tomography has become a field of intensive research. In SAR tomography, the vertical reflectivity function for every azimuth-range pixel is usually recovered by processing data collected using a defined repeat pass acquisition geometry. The most common approach is to generate a synthetic aperture in the elevation direction through imaging from a large number of parallel tracks. This imaging technique is appealing, since it is very simple. However, it has the draw back that large temporal baselines, which is the case for space-borne platforms, can severely affect the reconstruction. In an attempt to reduce the number of parallel tracks, we propose a new tomographic focusing approach that trades number of SAR images for correlations between neighboring azimuth-range pixels and polarimetric channels. As a matter of fact, this can be done under the framework of Distributed Compressed Sensing (DCS), which stems from Compressed Sensing (CS) theory, thus also exploiting sparsity in our tomographic signal. In addition, we address the problem of measurements affected by additive as well as multiplicative speckle noise. Results demonstrating the potential of the DCS methodology will be validated by using fully polarimetric L-band data acquired by the E-SAR sensor of DLR.},
    ISSN = {2153-6996},
    Keywords = {Airborne SAR, SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, Distributed Compressive Sensing, DCS methodology;E-SAR sensor;SAR image;azimuth-range pixel;distributed compressed sensing;elevation direction;fully polarimetric L-band data;multiplicative speckle noise;multisignal compressed sensing;pass acquisition geometry;polarimetric SAR tomography;polarimetric channel;space-borne radar platform;synthetic aperture radar;three dimensional imaging;tomographic focusing approach;tomographic signal;vertical reflectivity function;image reconstruction;image resolution;image sensors;radar imaging;radar polarimetry;radar resolution;spaceborne radar;speckle;synthetic aperture radar;tomography;} 
    }
    


  3. R. Brcic, A. Parizzi, M. Eineder, R. Bamler, and F. Meyer. Ionospheric effects in SAR interferometry: An analysis and comparison of methods for their estimation. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 1497-1500, July 2011. Keyword(s): ionospheric electromagnetic wave propagation, ionospheric techniques, radar interferometry, synthetic aperture radar, C-band system, L-band ALOS-PALSAR acquisitions, L-band system, P-band system, SAR signal, X-band frequencies, dispersive effects, ionospheric compensation, ionospheric effects, phase error, repeat-pass SAR interferometry, spaceborne SAR systems, topographic retrieval, wideband interferometry, Azimuth, Bandwidth, Delay, Estimation, Interferometry, Ionosphere, Synthetic aperture radar, delta-k, ionosphere, split-spectrum, wideband interferometry.
    Abstract: For spaceborne SAR (Synthetic Aperture Radar) systems, the dispersive effects of the ionosphere on the propagation of the SAR signal can be a significant source of phase error. While at X-band frequencies the effects are small, current and future P-, Land C-band systems would benefit from ionospheric compensation to avoid errors in topographic retrieval. In this paper the focus is on the effects of the ionosphere on repeat-pass SAR interferometry from Pthrough X-bands and methods for their estimation which are demonstrated on L-band ALOS-PALSAR acquisitions.

    @InProceedings{brcicParizziEinederBamlerMeyerIGARSS2011IonoInSARComparisonOfMethods,
    author = {R. Brcic and A. Parizzi and M. Eineder and R. Bamler and F. Meyer},
    title = {Ionospheric effects in {SAR} interferometry: An analysis and comparison of methods for their estimation},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2011},
    pages = {1497--1500},
    month = jul,
    abstract = {For spaceborne SAR (Synthetic Aperture Radar) systems, the dispersive effects of the ionosphere on the propagation of the SAR signal can be a significant source of phase error. While at X-band frequencies the effects are small, current and future P-, Land C-band systems would benefit from ionospheric compensation to avoid errors in topographic retrieval. In this paper the focus is on the effects of the ionosphere on repeat-pass SAR interferometry from Pthrough X-bands and methods for their estimation which are demonstrated on L-band ALOS-PALSAR acquisitions.},
    doi = {10.1109/IGARSS.2011.6049351},
    file = {:brcicParizziEinederBamlerMeyerIGARSS2011IonoInSARComparisonOfMethods.pdf:PDF},
    issn = {2153-6996},
    keywords = {ionospheric electromagnetic wave propagation, ionospheric techniques, radar interferometry, synthetic aperture radar, C-band system, L-band ALOS-PALSAR acquisitions, L-band system, P-band system, SAR signal, X-band frequencies, dispersive effects, ionospheric compensation, ionospheric effects, phase error, repeat-pass SAR interferometry, spaceborne SAR systems, topographic retrieval, wideband interferometry, Azimuth, Bandwidth, Delay, Estimation, Interferometry, Ionosphere, Synthetic aperture radar, delta-k, ionosphere, split-spectrum, wideband interferometry},
    owner = {ofrey},
    
    }
    


  4. A. Elsherbini and K. Sarabandi. Image distortion effects in subsurface SAR imaging of deserts and their correction technique. In Proc. IEEE Int. Geoscience and Remote Sensing Symp, pages 1075-1078, July 2011. Keyword(s): geophysical image processing, iterative methods, radar imaging, radar interferometry, remote sensing by radar, synthetic aperture radar, topography (Earth), arid regions, conventional SAR focusing techniques, correction technique, deserts, dual frequency InSAR, geometric distortion, image degradation, image distortion effects, interferometric coherence, interferometric synthetic aperture radar, iterative approach, nonplanar top surface, point spread function dispersion, scaled model measurements, subsurface SAR imaging, subsurface region imaging, subsurface topography estimation, Azimuth, Focusing, History, Optical surface waves, Solid modeling, Surface topography, Interferometric Synthetic Aperture Radar (InSAR), Radar Imaging, Subsurface Imaging, Terrain Mapping.
    @InProceedings{Elsherbini2011a,
    author = {A. Elsherbini and K. Sarabandi},
    title = {Image distortion effects in subsurface {SAR} imaging of deserts and their correction technique},
    booktitle = {Proc. IEEE Int. Geoscience and Remote Sensing Symp},
    year = {2011},
    month = jul,
    pages = {1075--1078},
    doi = {10.1109/IGARSS.2011.6049382},
    issn = {2153-6996},
    keywords = {geophysical image processing, iterative methods, radar imaging, radar interferometry, remote sensing by radar, synthetic aperture radar, topography (Earth), arid regions, conventional SAR focusing techniques, correction technique, deserts, dual frequency InSAR, geometric distortion, image degradation, image distortion effects, interferometric coherence, interferometric synthetic aperture radar, iterative approach, nonplanar top surface, point spread function dispersion, scaled model measurements, subsurface SAR imaging, subsurface region imaging, subsurface topography estimation, Azimuth, Focusing, History, Optical surface waves, Solid modeling, Surface topography, Interferometric Synthetic Aperture Radar (InSAR), Radar Imaging, Subsurface Imaging, Terrain Mapping},
    owner = {ofrey},
    
    }
    


  5. A. Elsherbini and K. Sarabandi. Subsurface topography mapping in deserts using two frequency SAR interferometry. In Proc. XXXth URSI General Assembly and Scientific Symp, pages 1-4, August 2011. Keyword(s): radar interferometry, synthetic aperture radar, terrain mapping, topography (Earth), InSAR inversion, Ka-InSAR, SAR image, VHF-InSAR, arid region, desert, height estimation, image distortion, scaled model measurement, subsurface topography mapping, top interface topography, two frequency SAR interferometry, Antennas, Azimuth, Extraterrestrial measurements, Focusing, Scattering, Surface topography.
    @InProceedings{Elsherbini2011,
    author = {A. Elsherbini and K. Sarabandi},
    title = {Subsurface topography mapping in deserts using two frequency {SAR} interferometry},
    booktitle = {Proc. XXXth URSI General Assembly and Scientific Symp},
    year = {2011},
    month = aug,
    pages = {1--4},
    doi = {10.1109/URSIGASS.2011.6050825},
    keywords = {radar interferometry, synthetic aperture radar, terrain mapping, topography (Earth), InSAR inversion, Ka-InSAR, SAR image, VHF-InSAR, arid region, desert, height estimation, image distortion, scaled model measurement, subsurface topography mapping, top interface topography, two frequency SAR interferometry, Antennas, Azimuth, Extraterrestrial measurements, Focusing, Scattering, Surface topography},
    owner = {ofrey},
    
    }
    


  6. H. Essen, S. Stanko, R. Sommer, W. Johannes, A. Wahlen, J. Wilcke, and S. Hantscher. Millimetre wave SAR for UAV operation. In Proc. Asia-Pacific Microwave Conference, pages 963-966, December 2011. Keyword(s): SAR Processing, W-Band, SUMATRA, Airborne SAR, UAV, Fraunhofer, CW radar, FM radar, Global Positioning System, airborne radar, autonomous aerial vehicles, high electron mobility transistors, millimetre wave amplifiers, millimetre wave field effect transistors, millimetre wave radar, synthetic aperture radar, Fraunhofer spin-off, UAV operation, W-band, advanced front-end technique, environmental monitoring, frequency 94 GHz, highly miniaturized FM-CW radar, low noise HEMT amplifiers, military reconnaissance, millimetre wave SAR system, millimetre wave technology, miniaturized radars, off-the-shelf GPS, sensor package, small airborne sensing aircraft, synthetic aperture radar, transmission equipment, Aircraft, Bandwidth, Chirp, Radar imaging, Sensors, Synthetic aperture radar, FM-CW waveform, UAV, millimetre waves, synthetic aperture radar.
    Abstract: Most recent developments in millimetre wave technology at W-band, especially the advance of medium power and low noise HEMT amplifiers, allow the set-up of miniaturized radars, operating with a wide RF bandwidth, achieving high range resolution. A highly miniaturized FM-CW radar at 94 GHz was developed and tested for SAR applications onboard small UAVs and within a sensor package to be used with a small airborne sensing aircraft. Advanced front-end technique was combined with off-the-shelf GPS and transmission equipment which is readily available. The main goal of the research project is to show, that new front-end technology in combination with achievable back-and components can lead to a SAR system, which is capable to serve a wide field of applications, as environmental monitoring, border control, agricultural applications and equally well can serve the needs of military reconnaissance applications. The paper describes the current state of the research project and gives the perspective of a later prototype production by a Fraunhofer Spin-off.

    @InProceedings{EssenEtAlAPMW2011SUMATRAWBandSARforUAV,
    author = {H. Essen and S. Stanko and R. Sommer and W. Johannes and A. Wahlen and J. Wilcke and S. Hantscher},
    booktitle = {Proc. Asia-Pacific Microwave Conference},
    title = {Millimetre wave {SAR} for {UAV} operation},
    year = {2011},
    month = dec,
    pages = {963-966},
    abstract = {Most recent developments in millimetre wave technology at W-band, especially the advance of medium power and low noise HEMT amplifiers, allow the set-up of miniaturized radars, operating with a wide RF bandwidth, achieving high range resolution. A highly miniaturized FM-CW radar at 94 GHz was developed and tested for SAR applications onboard small UAVs and within a sensor package to be used with a small airborne sensing aircraft. Advanced front-end technique was combined with off-the-shelf GPS and transmission equipment which is readily available. The main goal of the research project is to show, that new front-end technology in combination with achievable back-and components can lead to a SAR system, which is capable to serve a wide field of applications, as environmental monitoring, border control, agricultural applications and equally well can serve the needs of military reconnaissance applications. The paper describes the current state of the research project and gives the perspective of a later prototype production by a Fraunhofer Spin-off.},
    issn = {2165-4727},
    keywords = {SAR Processing, W-Band,SUMATRA, Airborne SAR, UAV, Fraunhofer,CW radar;FM radar;Global Positioning System;airborne radar;autonomous aerial vehicles;high electron mobility transistors;millimetre wave amplifiers;millimetre wave field effect transistors;millimetre wave radar;synthetic aperture radar;Fraunhofer spin-off;UAV operation;W-band;advanced front-end technique;environmental monitoring;frequency 94 GHz;highly miniaturized FM-CW radar;low noise HEMT amplifiers;military reconnaissance;millimetre wave SAR system;millimetre wave technology;miniaturized radars;off-the-shelf GPS;sensor package;small airborne sensing aircraft;synthetic aperture radar;transmission equipment;Aircraft;Bandwidth;Chirp;Radar imaging;Sensors;Synthetic aperture radar;FM-CW waveform;UAV;millimetre waves;synthetic aperture radar},
    owner = {ofrey},
    
    }
    


  7. Gianfranco Fornaro, A. Pauciullo, D. Reale, Xiao Xiang Zhu, and Richard Bamler. Peculiarities of urban area analysis with very high resolution interferometric SAR data. In Proc. Joint Urban Remote Sensing Event (JURSE), pages 185-188, 2011.
    @InProceedings{fornaroPauciulloRealeZhuBamler2011,
    Title = {Peculiarities of urban area analysis with very high resolution interferometric {SAR} data},
    Author = {Fornaro, Gianfranco and Pauciullo, A. and Reale, D. and Zhu, Xiao Xiang and Bamler, Richard},
    Booktitle = {Proc. Joint Urban Remote Sensing Event (JURSE)},
    Doi = {10.1109/JURSE.2011.5764751},
    Pages = {185--188},
    Year = {2011},
    Owner = {ofrey} 
    }
    


  8. Othmar Frey and Erich Meier. Characterizing the Backscattering Properties of a Forest by Polarimetric SAR Tomography at L- and P-Bands. In Proc. PolInSAR, 5th Int. Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry, ESA SP-695, Frascati, Italy, January 2011.
    @InProceedings{freyMeierPolInsAR2011:Tomo,
    author = {Othmar Frey and Erich Meier},
    title = {Characterizing the Backscattering Properties of a Forest by Polarimetric {SAR} Tomography at {L-} and {P}-Bands},
    booktitle = {Proc. PolInSAR, 5th Int. Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry},
    year = {2011},
    series = {ESA SP-695},
    address = {Frascati, Italy},
    month = jan,
    file = {:freyMeierPolinSAR2011.pdf:PDF},
    owner = {ofrey},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyMeierPolinSAR2011.pdf},
    
    }
    


  9. Othmar Frey, Erich Meier, and Irena Hajnsek. On the sensitivity of measured backscattering properties to variations of incidence angle and baselines in tomographic SAR data. In Proc. Int. Asia-Pacific Conf. on Synthetic Aperture Radar (APSAR), pages 1-4, September 2011. Keyword(s): Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, sensitivity analysis, synthetic aperture radar, SAR, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation.
    Abstract: SAR tomography at L- and P-bands reveals 3-D structural information of forested areas. A drawback, however, are the large number of samples, i.e. overflights, typically used for such configurations. Based on two fully-polarimetric tomographic SAR data sets, at L- and P-bands, we analyze the sensitivity of backscattering from a forest volume as measured by means of SAR tomography with respect to (1) a reduction of the total baseline by subsequently reducing the number of baselines, and (2), with respect to a variation of the incidence angle. In this paper, an excerpt of this sensitivity analysis is presented and discussed.

    @InProceedings{freyMeierHajnsekAPSAR2011,
    author = {Frey, Othmar and Meier, Erich and Hajnsek, Irena},
    title = {On the sensitivity of measured backscattering properties to variations of incidence angle and baselines in tomographic {SAR} data},
    booktitle = {Proc. Int. Asia-Pacific Conf. on Synthetic Aperture Radar ({APSAR})},
    year = {2011},
    pages = {1-4},
    month = sep,
    abstract = {SAR tomography at L- and P-bands reveals 3-D structural information of forested areas. A drawback, however, are the large number of samples, i.e. overflights, typically used for such configurations. Based on two fully-polarimetric tomographic SAR data sets, at L- and P-bands, we analyze the sensitivity of backscattering from a forest volume as measured by means of SAR tomography with respect to (1) a reduction of the total baseline by subsequently reducing the number of baselines, and (2), with respect to a variation of the incidence angle. In this paper, an excerpt of this sensitivity analysis is presented and discussed.},
    file = {:freyMeierHajnsekAPSAR2011.pdf:PDF},
    keywords = {Airborne radar, Array signal processing, Capon, Capon beamformer, L-band, P-band, SAR processing, SAR tomography, beamforming, Focusing, forestry, interferometry, InSAR, multibaseline, multiple signal classification, MUSIC, polarimetry, Remote Sensing, sensitivity analysis, synthetic aperture radar, SAR, three-dimensional imaging, 3-D imaging, time-domain back-projection, TDBP, tomography, Vegetation},
    pdf = {http://www.ifu-sar.ethz.ch/otfrey/SARbibliography/myPapers/freyMeierHajnsekAPSAR2011.pdf},
    url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6087139},
    
    }
    


  10. Othmar Frey, Maurizio Santoro, Charles L. Werner, and Urs Wegmuller. DEM-based SAR pixel area estimation for enhanced geocoding refinement and radiometric normalization. In Proc. FRINGE 2011, ESA SP-697, Frascati, Italy, September 2011. Keyword(s): SAR Processing, Geocoding, radiometric calibration, terrain-based radiometric normalization, Coregistration.
    Abstract: Precise terrain-corrected georeferencing of 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 DInSAR applications. For georeferencing a look-up table is calculated and 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, an approach based on angular relationships and a pixel-area based method are discussed in this paper. 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

    @InProceedings{freySantoroWegmullerWernerFRINGE2011,
    Title = {{DEM}-based {SAR} pixel area estimation for enhanced geocoding refinement and radiometric normalization},
    Author = {Othmar Frey and Maurizio Santoro and Charles L. Werner and Urs Wegmuller},
    Booktitle = {Proc. FRINGE 2011},
    Month = sep,
    Series = {ESA SP-697},
    Year = {2011},
    Abstract = {Precise terrain-corrected georeferencing of 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 DInSAR applications. For georeferencing a look-up table is calculated and 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, an approach based on angular relationships and a pixel-area based method are discussed in this paper. 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},
    Address = {Frascati, Italy},
    Keywords = {SAR Processing, Geocoding, radiometric calibration, terrain-based radiometric normalization, Coregistration},
    Owner = {ofrey} 
    }
    


  11. D. S. Goshi, Y. Liu, K. Mai, L. Bui, and Y. Shih. A W-band interferometric real-beam scanning FMCW imaging radar. In 2011 IEEE MTT-S International Microwave Symposium, pages 1-4, June 2011. Keyword(s): SAR Processing, W-Band, CW radar, FM radar, image enhancement, radar imaging, radar interferometry, synthetic aperture radar, 2D-based image enhancement, 3D volumetric sensor, RF characteristics, W-band interferometric real beam scanning FMCW imaging radar, frequency 10 Hz, height estimation, interferometric SAR radar system, interferometric technique, long post processing time, phase difference measurement, phase estimation measurement, real beam radar image, real time imaging system, Antenna measurements, Apertures, Imaging, Phase measurement, Radar antennas, Radar imaging, FMCW, imaging, interferometric, radar.
    Abstract: This paper presents an interferometric real-beam scanning FMCW imaging radar. As opposed to the more commonly discussed interferometric SAR radar system that requires a finite capture interval as well as traditionally long post-processing times, the proposed system is a real-time imaging system that generates a 10Hz real-beam radar image. The interferometric technique is proposed as a means to enhance the raw 2D-based image result by providing target height estimation from phase difference measurements, paving a foundation for a 3D volumetric sensor. The general concepts of the system will be discussed followed by details on the RF characteristics and performance. Lastly, the initial validation results of phase estimation measurements will be presented.

    @INPROCEEDINGS{goshiLiuMaiBuiShih2011WBandInterferometricFMCWRadar,
    author={D. S. Goshi and Y. Liu and K. Mai and L. Bui and Y. Shih},
    booktitle={2011 IEEE MTT-S International Microwave Symposium},
    title={A W-band interferometric real-beam scanning FMCW imaging radar},
    year={2011},
    volume={},
    number={},
    pages={1-4},
    abstract={This paper presents an interferometric real-beam scanning FMCW imaging radar. As opposed to the more commonly discussed interferometric SAR radar system that requires a finite capture interval as well as traditionally long post-processing times, the proposed system is a real-time imaging system that generates a 10Hz real-beam radar image. The interferometric technique is proposed as a means to enhance the raw 2D-based image result by providing target height estimation from phase difference measurements, paving a foundation for a 3D volumetric sensor. The general concepts of the system will be discussed followed by details on the RF characteristics and performance. Lastly, the initial validation results of phase estimation measurements will be presented.},
    keywords={SAR Processing, W-Band,CW radar;FM radar;image enhancement;radar imaging;radar interferometry;synthetic aperture radar;2D-based image enhancement;3D volumetric sensor;RF characteristics;W-band interferometric real beam scanning FMCW imaging radar;frequency 10 Hz;height estimation;interferometric SAR radar system;interferometric technique;long post processing time;phase difference measurement;phase estimation measurement;real beam radar image;real time imaging system;Antenna measurements;Apertures;Imaging;Phase measurement;Radar antennas;Radar imaging;FMCW;imaging;interferometric;radar},
    doi={10.1109/MWSYM.2011.5972724},
    ISSN={0149-645X},
    month=jun,
    owner = {ofrey},
    
    }
    


  12. Paco López-Dekker, Francesco De Zan, Thomas Borner, Marwan Younis, K. Papathanassiou, T. Guardabrazo, V. Bourlon, S. Ramongassie, N. Taveneau, Lars Ulander, D. Murdin, N. Rogers, Shaun Quegan, and R. Franco. BIOMASS end-to-end mission performance simulator. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 4249-4252, July 2011. Keyword(s): BIOMASS, P-band synthetic aperture radar, end-to-end mission performance simulator, fully quad-polarized image data acquistion, interferometric mode, module functional description, system architecture, data acquisition, radar imaging, radar interferometry, radar polarimetry, remote sensing by radar, vegetation, vegetation mapping.
    Abstract: This paper discusses the implementation of an end- to-end simulator for the BIOMASS mission. An overview of the system architecture is provided along with a functional description of the modules that comprise the simulator.

    @InProceedings{lopezDekkerEtalBiomassIGARSS2011,
    author = {L\'opez-Dekker, Paco and De Zan, Francesco and Borner, Thomas and Younis, Marwan and Papathanassiou, K. and Guardabrazo, T. and Bourlon, V. and Ramongassie, S. and Taveneau, N. and Ulander, Lars and Murdin, D. and Rogers, N. and Quegan, Shaun and Franco, R.},
    title = {{BIOMASS} end-to-end mission performance simulator},
    booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    year = {2011},
    pages = {4249-4252},
    month = jul,
    abstract = {This paper discusses the implementation of an end- to-end simulator for the BIOMASS mission. An overview of the system architecture is provided along with a functional description of the modules that comprise the simulator.},
    doi = {10.1109/IGARSS.2011.6050169},
    file = {:lopezDekkerEtalBiomassIGARSS2011.pdf:PDF},
    issn = {2153-6996},
    keywords = {BIOMASS;P-band synthetic aperture radar;end-to-end mission performance simulator;fully quad-polarized image data acquistion;interferometric mode;module functional description;system architecture;data acquisition;radar imaging;radar interferometry;radar polarimetry;remote sensing by radar;vegetation;vegetation mapping},
    owner = {ofrey},
    pdf = {../../../docs/lopezDekkerEtalBiomassIGARSS2011.pdf},
    
    }
    


  13. T. M. Marston, J. L. Kennedy, and P. L. Marston. Coherent and semi-coherent processing of limited-aperture circular synthetic aperture (CSAS) data. In Proc. OCEANS'11 MTS/IEEE KONA, pages 1-6, September 2011. Keyword(s): backscatter, radar imaging, synthetic aperture sonar, 360 degree scattering information, acoustic targets, backscattered echoes, circular synthetic aperture sonar, destructive interference, image clarity, image masking process, imaging algorithm, limited-aperture circular synthetic aperture data, remote environmental monitoring units, semi-coherent processing, sonar platform, time-domain information, unexploded ordnance objects, unmanned underwater vehicle, Acoustics, Aluminum, Apertures, Image reconstruction, Imaging, Synthetic aperture sonar, Tires, circular synthetic aperture sonar, classification, semicoherent imaging, subaperture, unexploded ordinance.
    @InProceedings{Marston2011,
    author = {T. M. Marston and J. L. Kennedy and P. L. Marston},
    title = {Coherent and semi-coherent processing of limited-aperture circular synthetic aperture (CSAS) data},
    booktitle = {Proc. OCEANS'11 MTS/IEEE KONA},
    year = {2011},
    month = sep,
    pages = {1--6},
    issn = {0197-7385},
    keywords = {backscatter, radar imaging, synthetic aperture sonar, 360 degree scattering information, acoustic targets, backscattered echoes, circular synthetic aperture sonar, destructive interference, image clarity, image masking process, imaging algorithm, limited-aperture circular synthetic aperture data, remote environmental monitoring units, semi-coherent processing, sonar platform, time-domain information, unexploded ordnance objects, unmanned underwater vehicle, Acoustics, Aluminum, Apertures, Image reconstruction, Imaging, Synthetic aperture sonar, Tires, circular synthetic aperture sonar, classification, semicoherent imaging, subaperture, unexploded ordinance},
    owner = {ofrey},
    
    }
    


  14. O. Ponce, P. Prats, M. Rodriguez-Cassola, R. Scheiber, and A. Reigber. Processing of Circular SAR trajectories with Fast Factorized Back-Projection. In Proc. IEEE Int. Geoscience and Remote Sensing Symp, pages 3692-3695, July 2011. Keyword(s): geophysical techniques, remote sensing by radar, Circular SAR trajectories, Germany, Kaufbeuren region, azimuth variance, computational time factor, fast factorized back-projection, graphics processor unit, Accuracy, Apertures, Focusing, Geometry, Graphics processing unit, Image resolution, Trajectory, Circular SAR (CSAR), Fast Back Projection (FBP), Graphics Processor Unit (GPU), focusing, polarimetry.
    @InProceedings{Ponce2011,
    author = {O. Ponce and P. Prats and M. Rodriguez-Cassola and R. Scheiber and A. Reigber},
    title = {Processing of Circular {SAR} trajectories with Fast Factorized Back-Projection},
    booktitle = {Proc. IEEE Int. Geoscience and Remote Sensing Symp},
    year = {2011},
    month = jul,
    pages = {3692--3695},
    doi = {10.1109/IGARSS.2011.6050026},
    issn = {2153-6996},
    keywords = {geophysical techniques, remote sensing by radar, Circular SAR trajectories, Germany, Kaufbeuren region, azimuth variance, computational time factor, fast factorized back-projection, graphics processor unit, Accuracy, Apertures, Focusing, Geometry, Graphics processing unit, Image resolution, Trajectory, Circular SAR (CSAR), Fast Back Projection (FBP), Graphics Processor Unit (GPU), focusing, polarimetry},
    owner = {ofrey},
    
    }
    


  15. Ricardo Portillo, Sarala Arunagiri, Patricia J. Teller, Song J. Park, Lam H. Nguyen, Joseph C. Deroba, and Dale Shires. Power versus performance tradeoffs of GPU-accelerated backprojection-based synthetic aperture radar image formation. In Proc. SPIE, volume 8060, pages 1-21, 2011. Keyword(s): SAR Processing, Time-Domain Back-Projection, TDBP, Back-Projection, Non-Linear Flight Tracks, Curvilinear SAR, GPU, GPGPU, Graphics Processing Unit, Focusing, Azimuth Focusing, Airborne SAR, Motion Compensation.
    @InProceedings{portilloArunagiriTellerParkNguyenDerobaShires2011:TDBPandGPU,
    Title = {Power versus performance tradeoffs of {GPU}-accelerated backprojection-based synthetic aperture radar image formation},
    Author = {Ricardo Portillo and Sarala Arunagiri and Patricia J. Teller and Song J. Park and Lam H. Nguyen and Joseph C. Deroba and Dale Shires},
    Booktitle = {Proc. SPIE},
    Doi = {10.1117/12.885120},
    Number = {1},
    Pages = {1-21},
    Volume = {8060},
    Year = {2011},
    ISSN = {0277786X},
    Keywords = {SAR Processing, Time-Domain Back-Projection, TDBP, Back-Projection, Non-Linear Flight Tracks, Curvilinear SAR, GPU, GPGPU, Graphics Processing Unit, Focusing, Azimuth Focusing, Airborne SAR, Motion Compensation},
    Owner = {ofrey},
    Pdf = {../../../docs/portilloArunagiriTellerParkNguyenDerobaShires2011.pdf} 
    }
    


  16. J. L. Prater and T. M. Marston. Partial synthetic aperture beamformer. In Proc. OCEANS'11 MTS/IEEE KONA, pages 1-5, September 2011. Keyword(s): array signal processing, autonomous underwater vehicles, image resolution, sonar imaging, synthetic aperture sonar, AUV technology, SAS, autonomous underwater vehicle, image resolution, nonlinear trajectories, partial synthetic aperture beamformer, synthetic aperture sonar, Apertures, Array signal processing, Image resolution, Synthetic aperture sonar, Trajectory, Vehicles, autonomatic target recognition, beamforming, synthetic aperture sonar.
    @InProceedings{Prater2011,
    author = {J. L. Prater and T. M. Marston},
    title = {Partial synthetic aperture beamformer},
    booktitle = {Proc. OCEANS'11 MTS/IEEE KONA},
    year = {2011},
    month = sep,
    pages = {1--5},
    issn = {0197-7385},
    keywords = {array signal processing, autonomous underwater vehicles, image resolution, sonar imaging, synthetic aperture sonar, AUV technology, SAS, autonomous underwater vehicle, image resolution, nonlinear trajectories, partial synthetic aperture beamformer, synthetic aperture sonar, Apertures, Array signal processing, Image resolution, Synthetic aperture sonar, Trajectory, Vehicles, autonomatic target recognition, beamforming, synthetic aperture sonar},
    owner = {ofrey},
    
    }
    


  17. Kenneth Ranney, Lam Nguyen, Francois Koenig, Getachew Kirose, Anthony Martone, Gregory Mazzaro, Kelly Sherbondy, Chi Tran, and Karl Kappra. Side-looking image formation with a maneuvering vehicle-mounted antenna array. In Proc. SPIE, volume 8021, pages 80211W, 2011. SPIE.
    Abstract: Researchers at the U.S. Army Research Laboratory (ARL) designed and fabricated the Synchronous Impulse REconstruction (SIRE) radar system in an effort to address fundamental questions about the utilization of low frequency, ultrawideband (UWB) radar. The SIRE system includes a receive array comprising 16 receive channels, and it is capable of operating in either a forward-looking or a side-looking mode. When operated in side-looking mode, it is capable of producing high-resolution Synthetic Aperture Radar (SAR) data. The SAR imaging algorithms, however, initially operated under the assumption that the vehicle followed a nearly linear trajectory throughout the data collection. Under this assumption, the introduction of vehicle path nonlinearities distorted the processed SAR imagery. In an effort to mitigate these effects, we first incorporated segmentation routines to eliminate highly non-linear portions of the path. We then enhanced the image formation algorithm, enabling it to process data collected from a non-linear vehicle trajectory. We describe the incorporated segmentation approaches and compare the imagery created before and after their incorporation. Next, we describe the modified image formation algorithm and present examples of output imagery produced by it. Finally, we compare imagery produced by the initial segmentation algorithm to imagery produced by the modified image-formation algorithm, highlighting the effects of segmentation parameter variation on the final SAR image.

    @InProceedings{ranneyNguyenKoenigKiroseMartoneMazzaroSherbondyTranKappra2011,
    author = {Kenneth Ranney and Lam Nguyen and Francois Koenig and Getachew Kirose and Anthony Martone and Gregory Mazzaro and Kelly Sherbondy and Chi Tran and Karl Kappra},
    title = {Side-looking image formation with a maneuvering vehicle-mounted antenna array},
    booktitle = {Proc. SPIE},
    year = {2011},
    volume = {8021},
    number = {1},
    pages = {80211W},
    publisher = {SPIE},
    abstract = {Researchers at the U.S. Army Research Laboratory (ARL) designed and fabricated the Synchronous Impulse REconstruction (SIRE) radar system in an effort to address fundamental questions about the utilization of low frequency, ultrawideband (UWB) radar. The SIRE system includes a receive array comprising 16 receive channels, and it is capable of operating in either a forward-looking or a side-looking mode. When operated in side-looking mode, it is capable of producing high-resolution Synthetic Aperture Radar (SAR) data. The SAR imaging algorithms, however, initially operated under the assumption that the vehicle followed a nearly linear trajectory throughout the data collection. Under this assumption, the introduction of vehicle path nonlinearities distorted the processed SAR imagery. In an effort to mitigate these effects, we first incorporated segmentation routines to eliminate highly non-linear portions of the path. We then enhanced the image formation algorithm, enabling it to process data collected from a non-linear vehicle trajectory. We describe the incorporated segmentation approaches and compare the imagery created before and after their incorporation. Next, we describe the modified image formation algorithm and present examples of output imagery produced by it. Finally, we compare imagery produced by the initial segmentation algorithm to imagery produced by the modified image-formation algorithm, highlighting the effects of segmentation parameter variation on the final SAR image.},
    coden = {PSISDG},
    doi = {10.1117/12.886231},
    file = {:ranneyNguyenKoenigKiroseMartoneMazzaroSherbondyTranKappra2011.pdf:PDF},
    issn = {0277786X},
    owner = {ofrey},
    pdf = {../../../docs/ranneyNguyenKoenigKiroseMartoneMazzaroSherbondyTranKappra2011.pdf},
    url = {http://dx.doi.org/10.1117/12.886231},
    
    }
    


  18. Stephan Stanko, Winfried Johannes, Rainer Sommer, Alfred Wahlen, Jörn. Wilcke, Helmut Essen, Axel Tessmann, and Ingmar Kallfass. SAR with MIRANDA - millimeterwave radar using analog and new digital approach. In Proc. European Radar Conference, pages 214-217, October 2011. Keyword(s): SAR Processing, FMCW, Frequency-Modulated Continuous-Wave, Ka-Band, W-Band, Airborne SAR, millimetre wave radar, radar imaging, synthetic aperture radar, IMU, MIRANDA, SAR, SAR-processing, UAV, analog approach, digital approach, frequency generation module, image scenes, inertial measurement unit, microlight, millimeterwave radar, synthetic aperture radar system, unmanned aerial vehicles, Chirp, Radar antennas, Radar imaging, Radar measurements, Synthetic aperture radar, Wavelength measurement.
    Abstract: The capability to image scenes from unmanned aerial vehicles (UAVs) even through bad weather conditions or dust clouds gets more and more important. In addition, modern synthetic aperture radar (SAR) systems giving very high resolution have to be light and small in size to fit in small aircrafts. In this paper we show a newly designed SAR system using a high flexible frequency generation module. The SAR- system was flown using a microlight and the radar raw data was transmitted to the ground and processed in real-time, so in an operational scenario the user can have an online image of the measurement. One crucial part of SAR-processing is the accuracy of the used inertial measurement unit (IMU). In this project we tested different kinds of these systems and determined the minimum requirements.

    @InProceedings{stankoJohannesSommerWahlenWilckeEssenTessmannKallfassEURAD2011MirandaFMCWSAR,
    author = {Stephan Stanko and Winfried Johannes and Rainer Sommer and Alfred Wahlen and J{\"o}rn. Wilcke and Helmut Essen and Axel Tessmann and Ingmar Kallfass},
    booktitle = {Proc. European Radar Conference},
    title = {{SAR} with {MIRANDA} - millimeterwave radar using analog and new digital approach},
    year = {2011},
    month = oct,
    pages = {214-217},
    abstract = {The capability to image scenes from unmanned aerial vehicles (UAVs) even through bad weather conditions or dust clouds gets more and more important. In addition, modern synthetic aperture radar (SAR) systems giving very high resolution have to be light and small in size to fit in small aircrafts. In this paper we show a newly designed SAR system using a high flexible frequency generation module. The SAR- system was flown using a microlight and the radar raw data was transmitted to the ground and processed in real-time, so in an operational scenario the user can have an online image of the measurement. One crucial part of SAR-processing is the accuracy of the used inertial measurement unit (IMU). In this project we tested different kinds of these systems and determined the minimum requirements.},
    file = {:stankoJohannesSommerWahlenWilckeEssenTessmannKallfassEURAD2011MirandaFMCWSAR.pdf:PDF},
    keywords = {SAR Processing, FMCW, Frequency-Modulated Continuous-Wave, Ka-Band, W-Band, Airborne SAR, millimetre wave radar;radar imaging;synthetic aperture radar;IMU;MIRANDA;SAR;SAR-processing;UAV;analog approach;digital approach;frequency generation module;image scenes;inertial measurement unit;microlight;millimeterwave radar;synthetic aperture radar system;unmanned aerial vehicles;Chirp;Radar antennas;Radar imaging;Radar measurements;Synthetic aperture radar;Wavelength measurement},
    owner = {ofrey},
    pdf = {../../../docs/stankoJohannesSommerWahlenWilckeEssenTessmannKallfassEURAD2011MirandaFMCWSAR.pdf},
    
    }
    


  19. Viet Thuy Vu, Thomas K. Sjogren, and Mats I. Pettersson. Fast backprojection algorithm for UWB bistatic SAR. In Proc. IEEE Radar Conf., pages 431-434, May 2011. Keyword(s): SAR Processing, Time-Domain Back-Projection, TDBP, Fast Factorized Back-Projection, FFBP, Back-Projection, UWB SAR, bistatic SAR, Motion Compensation, MoComp, UWB bistatic SAR, beamforming, bistatic fast backprojection algorithm, ground image plane, motion compensation, subaperture basis, subimage basis, time-domain characteristics, ultrawideband ultrawidebeam bistatic synthetic aperture radar, array signal processing, motion compensation, radar imaging, synthetic aperture radar, time-domain analysis, ultra wideband radar.
    Abstract: The paper introduces an algorithm for Ultrawide band Ultrawide-beam (UWB) bistatic Synthetic Aperture Radar (SAR). The algorithm works in time-domain and therefore inherits time-domain characteristics such as unlimited scene size, local processing and manageable motion compensation. The proposed algorithm is not limited by any configuration of bistatic SAR. The algorithm processes the UWB bistatic SAR data on a subaperture and subimage basis. This means, instead of backprojecting directly the SAR data to a ground image plane, the algorithm handles the data in two stages: beam forming and local backprojection. The algorithm is named Bistatic Fast Backprojection (BiFBP) and has been tested successfully with the simulated UWB bistatic SAR data.

    @InProceedings{vuSjogrenPetterssonRADARCON2011BistaticFFBP,
    Title = {Fast backprojection algorithm for {UWB} bistatic {SAR}},
    Author = {Viet Thuy Vu and Sjogren, Thomas K. and Pettersson, Mats I.},
    Booktitle = {Proc. IEEE Radar Conf.},
    Doi = {10.1109/RADAR.2011.5960575},
    Month = may,
    Pages = {431-434},
    Year = {2011},
    Abstract = {The paper introduces an algorithm for Ultrawide band Ultrawide-beam (UWB) bistatic Synthetic Aperture Radar (SAR). The algorithm works in time-domain and therefore inherits time-domain characteristics such as unlimited scene size, local processing and manageable motion compensation. The proposed algorithm is not limited by any configuration of bistatic SAR. The algorithm processes the UWB bistatic SAR data on a subaperture and subimage basis. This means, instead of backprojecting directly the SAR data to a ground image plane, the algorithm handles the data in two stages: beam forming and local backprojection. The algorithm is named Bistatic Fast Backprojection (BiFBP) and has been tested successfully with the simulated UWB bistatic SAR data.},
    ISSN = {1097-5659},
    Keywords = {SAR Processing, Time-Domain Back-Projection, TDBP, Fast Factorized Back-Projection, FFBP, Back-Projection, UWB SAR;bistatic SAR; Motion Compensation; MoComp,UWB bistatic SAR;beamforming;bistatic fast backprojection algorithm;ground image plane;motion compensation;subaperture basis;subimage basis;time-domain characteristics;ultrawideband ultrawidebeam bistatic synthetic aperture radar;array signal processing;motion compensation;radar imaging;synthetic aperture radar;time-domain analysis;ultra wideband radar},
    Owner = {ofrey} 
    }
    


  20. Viet Thuy Vu, Thomas K. Sjogren, and Mats I. Pettersson. Fast factorized backprojection algorithm for UWB SAR image reconstruction. In Proc. IEEE Int. Geosci. Remote Sens. Symp., pages 4237-4240, July 2011. Keyword(s): SAR Processing, Time-Domain Back-Projection, TDBP, Fast Factorized Back-Projection, FFBP, Back-Projection, UWB SAR, bistatic SAR, Motion Compensation, MoComp, migration handling, one beam forming stage, real time processing, synthetic aperture radar, time-domain characteristics, unlimited scene size, geophysical image processing, remote sensing by radar, synthetic aperture radar.
    Abstract: The fast factorized backprojection for bistatic SAR algorithm (BiFFBP), which processes the bistatic SAR data in more than one beam forming stage, is presented in this paper. The algorithm is developed on the bistatic fast backprojection algorithm SAR (BiFBP) and inherits time-domain characteristics such as unlimited scene size, real time processing, local processing, manageable motion compensation, and large range migration handling. Also, the algorithm works well with different kinds of bistatic configuration. For these reason, it is very suitable for UWB bistatic SAR processing. The pro- posed algorithm is tested successfully with simulated UWB bistatic SAR data.

    @InProceedings{vuSjogrenPetterssonIGARSS2011BistaticFFBP,
    Title = {Fast factorized backprojection algorithm for UWB SAR image reconstruction},
    Author = {Viet Thuy Vu and Sjogren, Thomas K. and Pettersson, Mats I.},
    Booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
    Doi = {10.1109/IGARSS.2011.6050166},
    Month = jul,
    Pages = {4237-4240},
    Year = {2011},
    Abstract = {The fast factorized backprojection for bistatic SAR algorithm (BiFFBP), which processes the bistatic SAR data in more than one beam forming stage, is presented in this paper. The algorithm is developed on the bistatic fast backprojection algorithm SAR (BiFBP) and inherits time-domain characteristics such as unlimited scene size, real time processing, local processing, manageable motion compensation, and large range migration handling. Also, the algorithm works well with different kinds of bistatic configuration. For these reason, it is very suitable for UWB bistatic SAR processing. The pro- posed algorithm is tested successfully with simulated UWB bistatic SAR data.},
    ISSN = {2153-6996},
    Keywords = {SAR Processing, Time-Domain Back-Projection, TDBP, Fast Factorized Back-Projection, FFBP, Back-Projection, UWB SAR;bistatic SAR; Motion Compensation; MoComp, migration handling;one beam forming stage;real time processing;synthetic aperture radar;time-domain characteristics;unlimited scene size;geophysical image processing;remote sensing by radar;synthetic aperture radar},
    Owner = {ofrey} 
    }
    


  21. Yuanyuan Wang, Xiao Xiang Zhu, and R. Bamler. Advanced coherence stacking technique using high resolution TerraSAR-X spotlight data. In Proc. Joint Urban Remote Sensing Event (JURSE), pages 233-236, 2011.
    @InProceedings{Wang2011a,
    Title = {Advanced coherence stacking technique using high resolution TerraSAR-X spotlight data},
    Author = {Yuanyuan Wang and Xiao Xiang Zhu and Bamler, R.},
    Booktitle = {Proc. Joint Urban Remote Sensing Event (JURSE)},
    Doi = {10.1109/JURSE.2011.5764763},
    Pages = {233--236},
    Year = {2011},
    Owner = {ofrey} 
    }
    


  22. Yuanyuan Wang, Xiao Xiang Zhu, and R. Bamler. Optimal estimation of distributed scatterer phase history parameters from meter-resolution SAR data. In Proc. IEEE Int. Geoscience and Remote Sensing Symp. (IGARSS), pages 3468-3471, 2011.
    @InProceedings{Wang2011,
    Title = {Optimal estimation of distributed scatterer phase history parameters from meter-resolution SAR data},
    Author = {Yuanyuan Wang and Xiao Xiang Zhu and Bamler, R.},
    Booktitle = {Proc. IEEE Int. Geoscience and Remote Sensing Symp. (IGARSS)},
    Doi = {10.1109/IGARSS.2011.6049967},
    Pages = {3468--3471},
    Year = {2011},
    Owner = {ofrey} 
    }
    


  23. Urs Wegmuller, Charles L. Werner, Othmar Frey, Tazio Strozzi, and Maurizio Santoro. Multi-pass ERS-ENVISAT cross-interferometry methods and results. In Proc. FRINGE 2011, ESA SP-697, Frascati, Italy, September 2011. Keyword(s): SAR Processing, Interferometry, InSAR, SAR Interferometry, Multi-pass InSAR, ERS, ENVISAT, ASAR, ERS-ENVISAT, C-Band, Spaceborne SAR.
    Abstract: ERS-ENVISAT Tandem (EET) cross-interferometry (CInSAR) pairs are characterized by long 2km baselines and short 28 minute time intervals. Over some sites multiple pairs are available. In our work we discuss multi-pass interferometric techniques and investigate for several applications, including DEM generation, mapping of fast motions and grounding line mapping for Antarctic ice sheets, the use of multiple EET pairs.

    @InProceedings{wegmullerWernerFreyStrozziSantoro2011,
    Title = {Multi-pass {ERS-ENVISAT} cross-interferometry methods and results},
    Author = {Urs Wegmuller and Charles L. Werner and Othmar Frey and Tazio Strozzi and Maurizio Santoro},
    Booktitle = {Proc. FRINGE 2011},
    Month = sep,
    Series = {ESA SP-697},
    Year = {2011},
    Abstract = {ERS-ENVISAT Tandem (EET) cross-interferometry (CInSAR) pairs are characterized by long 2km baselines and short 28 minute time intervals. Over some sites multiple pairs are available. In our work we discuss multi-pass interferometric techniques and investigate for several applications, including DEM generation, mapping of fast motions and grounding line mapping for Antarctic ice sheets, the use of multiple EET pairs.},
    Address = {Frascati, Italy},
    Keywords = {SAR Processing, Interferometry, InSAR, SAR Interferometry, Multi-pass InSAR, ERS, ENVISAT, ASAR, ERS-ENVISAT, C-Band, Spaceborne SAR},
    Owner = {ofrey} 
    }
    


  24. Charles L. Werner, Urs Wegmuller, Othmar Frey, and Maurizio Santoro. Interferometric processing of PALSAR Wide-Beam SCANSAR Data. In Proc. FRINGE 2011, ESA SP-697, Frascati, Italy, September 2011. Keyword(s): SAR Processing, Interferometry, InSAR, SAR Interferometry, PALSAR, ALOS PALSAR, ScanSAR, L-Band, Spaceborne SAR.
    Abstract: Processing of ScanSAR data for interferometric applications requires careful attention to the phase and position accuracy to obtain interferometric products with high correlation and continuous phase across the bursts. We describe an interferometric processing system developed for ScanSAR data acquired by the ALOS PALSAR instrument able to produce differential interferometric products with 350 km swath width that are without visible phase discontinuities between ScanSAR beams.

    @InProceedings{wernerWegmullerFreySantoro2011,
    Title = {Interferometric processing of {PALSAR} {W}ide-{B}eam {SCANSAR} Data},
    Author = {Charles L. Werner and Urs Wegmuller and Othmar Frey and Maurizio Santoro},
    Booktitle = {Proc. FRINGE 2011},
    Month = sep,
    Series = {ESA SP-697},
    Year = {2011},
    Abstract = {Processing of ScanSAR data for interferometric applications requires careful attention to the phase and position accuracy to obtain interferometric products with high correlation and continuous phase across the bursts. We describe an interferometric processing system developed for ScanSAR data acquired by the ALOS PALSAR instrument able to produce differential interferometric products with 350 km swath width that are without visible phase discontinuities between ScanSAR beams.},
    Address = {Frascati, Italy},
    Keywords = {SAR Processing, Interferometry, InSAR, SAR Interferometry, PALSAR, ALOS PALSAR, ScanSAR, L-Band, Spaceborne SAR},
    Owner = {ofrey} 
    }
    


  25. Xiao Xiang Zhu and R. Bamler. A fundamental bound for super-resolution --- with application to3D SAR imaging. In Proc. Joint Urban Remote Sensing Event (JURSE), pages 181-184, 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry.
    @InProceedings{Zhu2011f,
    author = {Xiao Xiang Zhu and Bamler, R.},
    booktitle = {Proc. Joint Urban Remote Sensing Event (JURSE)},
    title = {A fundamental bound for super-resolution --- with application to{3D} {SAR} imaging},
    year = {2011},
    pages = {181-184},
    doi = {10.1109/JURSE.2011.5764750},
    keywords = {SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry},
    owner = {ofrey},
    
    }
    


  26. Xiao Xiang Zhu and R. Bamler. Multi-component nonlinear motion estimation in differential SAR tomography - the time-warp method. In Proc. IEEE Int. Geoscience and Remote Sensing Symp. (IGARSS), pages 2409-2412, 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry.
    @InProceedings{Zhu2011a,
    Title = {Multi-component nonlinear motion estimation in differential SAR tomography - the time-warp method},
    Author = {Xiao Xiang Zhu and Bamler, R.},
    Booktitle = {Proc. IEEE Int. Geoscience and Remote Sensing Symp. (IGARSS)},
    Doi = {10.1109/IGARSS.2011.6049696},
    Pages = {2409-2412},
    Year = {2011},
    Keywords = {SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry},
    Owner = {ofrey} 
    }
    


  27. Xiao Xiang Zhu and R. Bamler. Sparse reconstrcution techniques for SAR tomography. In Proc. 17th Int Digital Signal Processing (DSP) Conf, pages 1-8, 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry.
    @InProceedings{Zhu2011e,
    author = {Xiao Xiang Zhu and Bamler, R.},
    booktitle = {Proc. 17th Int Digital Signal Processing (DSP) Conf},
    title = {Sparse reconstrcution techniques for SAR tomography},
    year = {2011},
    pages = {1-8},
    doi = {10.1109/ICDSP.2011.6005022},
    keywords = {SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry},
    owner = {ofrey},
    
    }
    


  28. Xiao Xiang Zhu and R. Bamler. Within the resolution cell: Super-resolution in tomographic SAR imaging. In Proc. IEEE Int. Geoscience and Remote Sensing Symp. (IGARSS), pages 2401-2404, 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry.
    @InProceedings{Zhu2011c,
    author = {Xiao Xiang Zhu and Bamler, R.},
    booktitle = {Proc. IEEE Int. Geoscience and Remote Sensing Symp. (IGARSS)},
    title = {Within the resolution cell: Super-resolution in tomographic SAR imaging},
    year = {2011},
    pages = {2401-2404},
    doi = {10.1109/IGARSS.2011.6049694},
    keywords = {SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry},
    owner = {ofrey},
    
    }
    


  29. Xiao Xiang Zhu, Xuan Wang, and Richard Bamler. Compressive sensing for image fusion - with application to pan-sharpening. In Proc. IEEE Int. Geoscience and Remote Sensing Symp. (IGARSS), pages 2793-2796, 2011. Keyword(s): SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry.
    @InProceedings{Zhu2011,
    Title = {Compressive sensing for image fusion - with application to pan-sharpening},
    Author = {Xiao Xiang Zhu and Xuan Wang and Richard Bamler},
    Booktitle = {Proc. IEEE Int. Geoscience and Remote Sensing Symp. (IGARSS)},
    Doi = {10.1109/IGARSS.2011.6049794},
    Pages = {2793-2796},
    Year = {2011},
    Keywords = {SAR Processing, SAR Tomography, Tomography, Compressive Sensing, CS, InSAR, SAR Interferometry, Interferometry},
    Owner = {ofrey} 
    }
    


Miscellaneous

  1. FRINGE 2011 Sorted Recommendations, September 2011.
    @Misc{FRINGE2011SortedRecommendations,
    Title = {FRINGE 2011 Sorted Recommendations},
    Month = sep,
    Organization = {ESA},
    Year = {2011},
    Address = {Frascati, Italy} 
    }
    


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Please note that access to full text PDF versions of papers is restricted to the Chair of Earth Observation and Remote Sensing, Institute of Environmental Engineering, ETH Zurich.
Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright.

This collection of SAR literature is far from being complete.
It is rather a collection of papers which I store in my literature data base. Hence, the list of publications under PUBLICATIONS OF AUTHOR'S NAME should NOT be mistaken for a complete bibliography of that author.




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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