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Publications of year 2003

Thesis

  1. Hayden J. Callow. Signal Processing for Synthetic Aperture Sonar Image Enhancement. PhD thesis, University of Canterbury, 2003.
    Keywords: SAR Processing, Autofocus, Phase Gradient Autofocus, Stripmap, Stripmap PGA, Stripmap Phase Gradient Autofocus, SAS, Synthetic Aperture Sonar.
    Abstract: This thesis contains a description of SAS processing algorithms, offering improvements in Fourier-based reconstruction, motion-compensation, and autofocus. Fourier-based image reconstruction is reviewed and improvements shown as the result of improved system modelling. A number of new algorithms based on the wavenumber algorithm for correcting second order effects are proposed. In addition, a new framework for describing multiple-receiver reconstruction in terms of the bistatic geometry is presented and is a useful aid to understanding. Motion-compensation techniques for allowing Fourier-based reconstruction in widebeam geometries suffering large-motion errors are discussed. A motion-compensation algorithm exploiting multiple receiver geometries is suggested and shown to provide substantial improvement in image quality. New motion compensation techniques for yaw correction using the wavenumber algorithm are discussed. A common framework for describing phase estimation is presented and techniques from a number of fields are reviewed within this framework. In addition a new proof is provided outlining the relationship between eigenvector-based autofocus phase estimation kernels and the phase-closure techniques used astronomical imaging. Micronavigation techniques are reviewed and extensions to the shear average single-receiver micronavigation technique result in a 3-4 fold performance improvement when operating on high-contrast images. The stripmap phase gradient autofocus (SPGA) algorithm is developed and extends spotlight SAR PGA to the wide-beam, wide-band stripmap geometries common in SAS imaging. SPGA supersedes traditional PGA-based stripmap autofocus algorithms such as mPGA and PCA -- the relationships between SPGA and these algorithms is discussed. SPGA's operation is verified on simulated and field-collected data where it provides significant image improvement. SPGA with phase-curvature based estimation is shown and found to perform poorly compared with phase-gradient techniques. The operation of SPGA on data collected from Sydney Harbour is shown with SPGA able to improve resolution to near the diffraction-limit. Additional analysis of practical stripmap autofocus operation in presence of undersampling and space-invariant blurring is presented with significant comment regarding the difficulties inherent in autofocusing field-collected data. Field-collected data from trials in Sydney Harbour is presented along with associated autofocus results from a number of algorithms. 

    @PHDTHESIS{Callow2003PhD:PGAforSAS,
author = {Hayden J. Callow},
title = {{Signal Processing for Synthetic Aperture Sonar Image Enhancement}},
school = {University of Canterbury},
year = {2003},
abstract = {This thesis contains a description of SAS processing algorithms, offering improvements in Fourier-based reconstruction, motion-compensation, and autofocus. Fourier-based image reconstruction is reviewed and improvements shown as the result of improved system modelling. A number of new algorithms based on the wavenumber algorithm for correcting second order effects are proposed. In addition, a new framework for describing multiple-receiver reconstruction in terms of the bistatic geometry is presented and is a useful aid to understanding. Motion-compensation techniques for allowing Fourier-based reconstruction in widebeam geometries suffering large-motion errors are discussed. A motion-compensation algorithm exploiting multiple receiver geometries is suggested and shown to provide substantial improvement in image quality. New motion compensation techniques for yaw correction using the wavenumber algorithm are discussed. A common framework for describing phase estimation is presented and techniques from a number of fields are reviewed within this framework. In addition a new proof is provided outlining the relationship between eigenvector-based autofocus phase estimation kernels and the phase-closure techniques used astronomical imaging. Micronavigation techniques are reviewed and extensions to the shear average single-receiver micronavigation technique result in a 3-4 fold performance improvement when operating on high-contrast images. The stripmap phase gradient autofocus (SPGA) algorithm is developed and extends spotlight SAR PGA to the wide-beam, wide-band stripmap geometries common in SAS imaging. SPGA supersedes traditional PGA-based stripmap autofocus algorithms such as mPGA and PCA -- the relationships between SPGA and these algorithms is discussed. SPGA's operation is verified on simulated and field-collected data where it provides significant image improvement. SPGA with phase-curvature based estimation is shown and found to perform poorly compared with phase-gradient techniques. The operation of SPGA on data collected from Sydney Harbour is shown with SPGA able to improve resolution to near the diffraction-limit. Additional analysis of practical stripmap autofocus operation in presence of undersampling and space-invariant blurring is presented with significant comment regarding the difficulties inherent in autofocusing field-collected data. Field-collected data from trials in Sydney Harbour is presented along with associated autofocus results from a number of algorithms.},
keywords = {SAR Processing, Autofocus, Phase Gradient Autofocus, Stripmap, Stripmap PGA, Stripmap Phase Gradient Autofocus, SAS, Synthetic Aperture Sonar},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/Callow2003PhD.pdf},
url = {http://www.elec.canterbury.ac.nz/research/acoustics/pubs/theses/Callow_thesis_2003.pdf} 
}


Articles in journal or book chapters

  1. Silvia Cimmino, Giorgio Franceschetti, Antonio Iodice, Daniele Riccio, and Giuseppe Ruello. Efficient Spotlight SAR Raw Signal Simulation of Extended Scenes. IEEE Transactions on Geoscience and Remote Sensing, 41(10):2329-2337, October 2003.
    Keywords: SAR Processing, Simulation, SAR Simulator, Raw Data Simulator, Spotlight SAR.
    Abstract: Synthetic aperture radar (SAR) raw signal simulation is a powerful tool for designing new sensors, testing processing algorithms, planning missions, and devising inversion algorithms. In this paper, a spotlight SAR raw signal simulator for distributed targets is presented. The proposed procedure is based on a Fourier domain analysis: a proper analytical reformulation of the spotlight SAR raw signal expression is presented. It is shown that this reformulation allows us to design a very efficient simulation scheme that employs fast Fourier transform codes. Accordingly, the computational load is dramatically reduced with respect to a time-domain simulation and this, for the first time, makes spotlight simulation of extended scenes feasible. 

    @ARTICLE{CimFrancesIodiceRiccio03:Simulation,
author = {Silvia Cimmino and Giorgio Franceschetti and Antonio Iodice and Daniele Riccio and Giuseppe Ruello},
title = {{Efficient Spotlight SAR Raw Signal Simulation of Extended Scenes}},
journal = {IEEE Transactions on Geoscience and Remote Sensing},
year = {2003},
volume = {41},
pages = {2329-2337},
number = {10},
month = Oct,
abstract = {Synthetic aperture radar (SAR) raw signal simulation is a powerful tool for designing new sensors, testing processing algorithms, planning missions, and devising inversion algorithms. In this paper, a spotlight SAR raw signal simulator for distributed targets is presented. The proposed procedure is based on a Fourier domain analysis: a proper analytical reformulation of the spotlight SAR raw signal expression is presented. It is shown that this reformulation allows us to design a very efficient simulation scheme that employs fast Fourier transform codes. Accordingly, the computational load is dramatically reduced with respect to a time-domain simulation and this, for the first time, makes spotlight simulation of extended scenes feasible.},
keywords = {SAR Processing, Simulation, SAR Simulator, Raw Data Simulator, Spotlight SAR},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/CimFrancesIodiceRiccio03.pdf},
url = {http://ieeexplore.ieee.org/iel5/36/27742/01237398.pdf} 
}


  2. F.M. Dickey, L.A. Romero, J.M. DeLaurentis, and A.W. Doerry. Super-resolution, degrees of freedom and synthetic aperture radar. Radar, Sonar and Navigation, IEE Proceedings -, 150(6):419--429, 2003.
    Keywords: SAR Processing, SAR Tomography, Tomography, Fourier transforms, eigenvalues and eigenfunctions, extrapolation, inverse problems, mathematical operators, radar imaging, radar resolution, synthetic aperture radar, Fourier transform extrapolation, SAR images, degrees of freedom, eigenvalue spectrum, ill posed problem, operator inversion problem, super-resolution, synthetic aperture radar.
    Abstract: Super-resolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realised. The potential application of super-resolution concepts to synthetic aperture radar is investigated. The analytical basis for super-resolution theory is discussed. The application of the concept to synthetic aperture radar is investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. However, it is shown that it is the particular form of the eigenvalue spectrum of the associated operator that precludes any significant resolution enhancement of synthetic aperture radar images. A criterion for judging super-resolution processing of an image is presented. 

    @ARTICLE{dickeyRomeroDeLaurentisDoerry03:Tomo,
author = {Dickey, F.M. and Romero, L.A. and DeLaurentis, J.M. and Doerry, A.W.},
title = {Super-resolution, degrees of freedom and synthetic aperture radar},
journal = {Radar, Sonar and Navigation, IEE Proceedings -},
year = {2003},
volume = {150},
pages = {419--429},
number = {6},
abstract = {Super-resolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realised. The potential application of super-resolution concepts to synthetic aperture radar is investigated. The analytical basis for super-resolution theory is discussed. The application of the concept to synthetic aperture radar is investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. However, it is shown that it is the particular form of the eigenvalue spectrum of the associated operator that precludes any significant resolution enhancement of synthetic aperture radar images. A criterion for judging super-resolution processing of an image is presented.},
issn = {1350-2395},
keywords = {SAR Processing, SAR Tomography, Tomography, Fourier transforms, eigenvalues and eigenfunctions, extrapolation, inverse problems, mathematical operators, radar imaging, radar resolution, synthetic aperture radar, Fourier transform extrapolation, SAR images, degrees of freedom, eigenvalue spectrum, ill posed problem, operator inversion problem, super-resolution, synthetic aperture radar},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/dickeyRomeroDelaurentisDoerryTomo03.pdf},
url = {http://ieeexplore.ieee.org/iel5/2198/28064/01254301.pdf} 
}


  3. Fred M. Dickey, Louis A. Romero, and Armin W. Doerry. Window functions for imaging radar: a maximum energy approach to contiguous and notched spectrums. Optical Engineering, 42(7):2113-2128, 2003.
    Keywords: SAR Processing, radar imaging, synthetic aperture radar, sidelobes, window functions, filtering, notched spectrum.
    Abstract: Imaging systems such as synthetic aperture radar collect band-limited data from which an image of a target scene is rendered. The band-limited nature of the data generates sidelobes, or spilled energy, most evident in the neighborhood of bright point-like objects. It is generally considered desirable to minimize these sidelobes, even at the expense of some generally small increase in system bandwidth. This is accomplished by shaping the spectrum with window functions prior to inversion or transformation into an image. A window function that minimizes sidelobe energy can be constructed based on prolate spheroidal wave functions. A parametric design procedure allows doing so, even with constraints on allowable increases in system bandwidth. This approach is extended to accommodate spectral notches or holes, although the guaranteed minimum sidelobe energy can be quite high in this case. Interestingly, for a fixed bandwidth, the minimum mean-squared-error image rendering of a target scene is achieved with no windowing at all (rectangular or boxcar window). 

    @ARTICLE{DickeyRomeroDoerry2003,
author = {Fred M. Dickey and Louis A. Romero and Armin W. Doerry},
title = {Window functions for imaging radar: a maximum energy approach to contiguous and notched spectrums},
journal = {Optical Engineering},
year = {2003},
volume = {42},
pages = {2113-2128},
number = {7},
abstract = {Imaging systems such as synthetic aperture radar collect band-limited data from which an image of a target scene is rendered. The band-limited nature of the data generates sidelobes, or spilled energy, most evident in the neighborhood of bright point-like objects. It is generally considered desirable to minimize these sidelobes, even at the expense of some generally small increase in system bandwidth. This is accomplished by shaping the spectrum with window functions prior to inversion or transformation into an image. A window function that minimizes sidelobe energy can be constructed based on prolate spheroidal wave functions. A parametric design procedure allows doing so, even with constraints on allowable increases in system bandwidth. This approach is extended to accommodate spectral notches or holes, although the guaranteed minimum sidelobe energy can be quite high in this case. Interestingly, for a fixed bandwidth, the minimum mean-squared-error image rendering of a target scene is achieved with no windowing at all (rectangular or boxcar window).},
keywords = {SAR Processing, radar imaging, synthetic aperture radar, sidelobes, window functions, filtering,notched spectrum},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/DickeyRomeroDoerry2003.pdf},
publisher = {SPIE},
url = {http://link.aip.org/link/?JOE/42/2113/1} 
}


  4. G. Fornaro, F. Serafino, and F. Soldovieri. Three-dimensional focusing with multipass SAR data. Geoscience and Remote Sensing, IEEE Transactions on, 41(3):507--517, 2003.
    Keywords: SAR Processing, SAR Tomography, Tomography, focusing, synthetic aperture radar, 3D tomography reconstruction, linear inverse problem, multipass SAR data, multipass synthetic aperture radar data, nonuniform orbit separation, processing technique, scattering mechanism, singular value decomposition, volumetric scattering.
    Abstract: Deals with the use of multipass synthetic aperture radar (SAR) data in order to achieve three-dimensional tomography reconstruction in presence of volumetric scattering. Starting from azimuth- and range-focused SAR data relative to the same area, neglecting any mutual interaction between the targets, and assuming the propagation in homogeneous media, we investigate the possibility to focus the data also in the elevation direction. The problem is formulated in the framework of linear inverse problem and the solution makes use of the singular value decomposition of the relevant operator. This allows us to properly take into account nonuniform orbit separation and to exploit a priori knowledge regarding the size of the volume interested by the scattering mechanism, thus leading to superresolution in the elevation direction. Results obtained on simulated data demonstrate the feasibility of the proposed processing technique. 

    @ARTICLE{fornaroSerafinoSoldovieri03:Tomo,
author = {Fornaro, G. and Serafino, F. and Soldovieri, F.},
title = {Three-dimensional focusing with multipass SAR data},
journal = {Geoscience and Remote Sensing, IEEE Transactions on},
year = {2003},
volume = {41},
pages = {507--517},
number = {3},
abstract = {Deals with the use of multipass synthetic aperture radar (SAR) data in order to achieve three-dimensional tomography reconstruction in presence of volumetric scattering. Starting from azimuth- and range-focused SAR data relative to the same area, neglecting any mutual interaction between the targets, and assuming the propagation in homogeneous media, we investigate the possibility to focus the data also in the elevation direction. The problem is formulated in the framework of linear inverse problem and the solution makes use of the singular value decomposition of the relevant operator. This allows us to properly take into account nonuniform orbit separation and to exploit a priori knowledge regarding the size of the volume interested by the scattering mechanism, thus leading to superresolution in the elevation direction. Results obtained on simulated data demonstrate the feasibility of the proposed processing technique.},
issn = {0196-2892},
keywords = {SAR Processing, SAR Tomography, Tomography,focusing, synthetic aperture radar, 3D tomography reconstruction, linear inverse problem, multipass SAR data, multipass synthetic aperture radar data, nonuniform orbit separation, processing technique, scattering mechanism, singular value decomposition, volumetric scattering},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/fornaroSerafinoSoldovieriTomo03.pdf},
url = {http://ieeexplore.ieee.org/iel5/36/26979/01198642.pdf} 
}


  5. Jong-Sen Lee, S. R. Cloude, K. P. Papathanassiou, M. R. Grunes, and I. H. Woodhouse. Speckle filtering and coherence estimation of polarimetric SAR interferometry data for forest applications. IEEE_J_GRS, 41(10):2254-2263, October 2003.
    Keywords: SAR Processing, Forest, Forest parameters, biomass, averaging, boxcar filter, coherence estimation, forest applications, forest heights, ground topography, interferometric coherence, neighboring pixels, polarimetric SAR interferometry data, polarimetric interferometry matrix, polarimetric synthetic aperture radar interferometry, random volume, scattering characteristics, speckle filtering, adaptive filters, forestry, radar imaging, radar polarimetry, radiowave interferometry, remote sensing by radar, speckle, synthetic aperture radar;.
    Abstract: Recently, polarimetric synthetic aperture radar (SAR) interferometry has generated much interest for forest applications. Forest heights and ground topography can be extracted based on interferometric coherence using a random volume over ground coherent mixture model. The coherence estimation is of paramount importance for the accuracy of forest height estimation. The coherence (or correlation coefficient) is a statistical average of neighboring pixels of similar scattering characteristics. The commonly used algorithm is the boxcar filter, which has the deficiency of indiscriminate averaging of neighboring pixels. The result is that coherence values are lower than they should be. In this paper, we propose a new algorithm to improve the accuracy in the coherence estimation based on speckle filtering of the 6 times;6 polarimetric interferometry matrix. Simulated images are used to verify the effectiveness of this adaptive algorithm. German Aerospace Center (DLR) L-Band E-SAR data are applied to demonstrate the improved accuracy in coherence and in forest height estimation. 

    @ARTICLE{leeCloudePapthanassiouGrunesWoodhouse2003:PolInSARForestApplications,
author={Jong-Sen Lee and Cloude, S. R. and Papathanassiou, K. P. and Grunes, M. R. and Woodhouse, I. H.},
journal=IEEE_J_GRS,
title={Speckle filtering and coherence estimation of polarimetric {SAR} interferometry data for forest applications},
year={2003},
month=oct,
volume={41},
number={10},
pages={2254-2263},
abstract={Recently, polarimetric synthetic aperture radar (SAR) interferometry has generated much interest for forest applications. Forest heights and ground topography can be extracted based on interferometric coherence using a random volume over ground coherent mixture model. The coherence estimation is of paramount importance for the accuracy of forest height estimation. The coherence (or correlation coefficient) is a statistical average of neighboring pixels of similar scattering characteristics. The commonly used algorithm is the boxcar filter, which has the deficiency of indiscriminate averaging of neighboring pixels. The result is that coherence values are lower than they should be. In this paper, we propose a new algorithm to improve the accuracy in the coherence estimation based on speckle filtering of the 6 times;6 polarimetric interferometry matrix. Simulated images are used to verify the effectiveness of this adaptive algorithm. German Aerospace Center (DLR) L-Band E-SAR data are applied to demonstrate the improved accuracy in coherence and in forest height estimation.},
keywords={SAR Processing, Forest, Forest parameters, biomass, averaging; boxcar filter; coherence estimation; forest applications; forest heights; ground topography; interferometric coherence; neighboring pixels; polarimetric SAR interferometry data; polarimetric interferometry matrix; polarimetric synthetic aperture radar interferometry; random volume; scattering characteristics; speckle filtering; adaptive filters; forestry; radar imaging; radar polarimetry; radiowave interferometry; remote sensing by radar; speckle; synthetic aperture radar;},
doi={10.1109/TGRS.2003.817196},
ISSN={0196-2892},

}


  6. Jian Li, Petre Stoica, and Zhisong Wang. On robust Capon beamforming and diagonal loading. Signal Processing, IEEE Transactions on [see also Acoustics, Speech, and Signal Processing, IEEE Transactions on], 51(7):1702--1715, 2003.
    Keywords: SAR Processing, Capon, Spectral Estimation, Beamforming, array signal processing, interference suppression, parameter estimation, signal resolution, SOI power estimation, SOI steering vector, adaptive arrays, array steering vector, data-independent beamformer, diagonal loading, interference rejection, robust Capon beamforming, signal of interest, signal resolution, standard Capon beamformer, uncertain steering vectors, uncertainty set.
    Abstract: The Capon (1969) beamformer has better resolution and much better interference rejection capability than the standard (data-independent) beamformer, provided that the array steering vector corresponding to the signal of interest (SOI) is accurately known. However, whenever the knowledge of the SOI steering vector is imprecise (as is often the case in practice), the performance of the Capon beamformer may become worse than that of the standard beamformer. Diagonal loading (including its extended versions) has been a popular approach to improve the robustness of the Capon beamformer. We show that a natural extension of the Capon beamformer to the case of uncertain steering vectors also belongs to the class of diagonal loading approaches, but the amount of diagonal loading can be precisely calculated based on the uncertainty set of the steering vector. The proposed robust Capon beamformer can be efficiently computed at a comparable cost with that of the standard Capon beamformer. Its excellent performance for SOI power estimation is demonstrated via a number of numerical examples. 

    @ARTICLE{LiStoicaWang2003:RobustCapon,
author = {Li, Jian and Stoica, Petre and Wang, Zhisong},
title = {{On robust Capon beamforming and diagonal loading}},
journal = {Signal Processing, IEEE Transactions on [see also Acoustics, Speech, and Signal Processing, IEEE Transactions on]},
year = {2003},
volume = {51},
pages = {1702--1715},
number = {7},
abstract = {The Capon (1969) beamformer has better resolution and much better interference rejection capability than the standard (data-independent) beamformer, provided that the array steering vector corresponding to the signal of interest (SOI) is accurately known. However, whenever the knowledge of the SOI steering vector is imprecise (as is often the case in practice), the performance of the Capon beamformer may become worse than that of the standard beamformer. Diagonal loading (including its extended versions) has been a popular approach to improve the robustness of the Capon beamformer. We show that a natural extension of the Capon beamformer to the case of uncertain steering vectors also belongs to the class of diagonal loading approaches, but the amount of diagonal loading can be precisely calculated based on the uncertainty set of the steering vector. The proposed robust Capon beamformer can be efficiently computed at a comparable cost with that of the standard Capon beamformer. Its excellent performance for SOI power estimation is demonstrated via a number of numerical examples.},
booktitle = {Signal Processing, IEEE Transactions on [see also Acoustics, Speech, and Signal Processing, IEEE Transactions on]},
issn = {1053-587X},
keywords = {SAR Processing, Capon, Spectral Estimation, Beamforming, array signal processing, interference suppression, parameter estimation, signal resolution, SOI power estimation, SOI steering vector, adaptive arrays, array steering vector, data-independent beamformer, diagonal loading, interference rejection, robust Capon beamforming, signal of interest, signal resolution, standard Capon beamformer, uncertain steering vectors, uncertainty set},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/LiStoicaWang2003.pdf},
url = {http://ieeexplore.ieee.org/iel5/78/27152/01206680.pdf} 
}


  7. F. Lombardini, M. Montanari, and F. Gini. Reflectivity estimation for multibaseline interferometric radar imaging of layover extended sources. IEEE Transactions on Signal Processing, 51(6):1508-1519, June 2003.
    Keywords: SAR Processing, Tomography, SAR Tomography, Multi-baseline SAR, Interferometry, SAR Interferometry, AWGN, Monte Carlo methods, amplitude estimation, radar imaging, radiowave interferometry, synthetic aperture radar APES, Capon's approach, InSAR, Monte Carlo simulation, RELAX, SAR, additive white Gaussian noise, amplitude estimation, complex orography, component sinusoidal signal, hybrid spectral estimators, layover extended sources, multibaseline interferometric radar imaging, multibaseline operation, multiplicative complex correlated noise, nonparametric estimators, parametric estimators, reflectivity estimation, spatial frequency estimation, synthetic aperture radar interferometry, terrain height, undistorted multibaseline image formation.
    Abstract: In recent years, there has been great interest in exploiting the advanced multibaseline operation of synthetic aperture radar interferometry (InSAR) for solving layover effects from complex orography, which can degrade both SAR and InSAR imagery of terrain radar reflectivity and height. In this work, the problem of retrieving radar reflectivity of layover areas is addressed. It is formulated as the problem of estimating a multicomponent sinusoidal signal corrupted by multiplicative complex correlated noise and additive white Gaussian noise. Application of nonparametric [e.g., Capon, amplitude and phase estimation filter (APES)], parametric [least squares, modern parametric RELAXation spectral estimator (RELAX)], and hybrid spectral estimators for amplitude estimation is investigated for a multilook scenario. In particular, the multilook extensions of RELAX and APES are applied to the interferometric problem. Performance analysis is investigated through a Cramer-Rao lower bound calculation and Monte Carlo simulation. The method of least squares, coupled with Capon's approach to spatial frequency estimation, multilook APES, and multilook RELAX turn out to provide accurate reflectivity estimates for undistorted multibaseline image formation of layover areas. 

    @ARTICLE{lombardiniMontanariGini2003:Tomo,
author = {Lombardini, F. and Montanari, M. and Gini, F.},
title = {Reflectivity estimation for multibaseline interferometric radar imaging of layover extended sources},
journal = {IEEE Transactions on Signal Processing},
year = {2003},
volume = {51},
pages = { 1508-1519},
number = {6},
month = {jun},
abstract = {In recent years, there has been great interest in exploiting the advanced multibaseline operation of synthetic aperture radar interferometry (InSAR) for solving layover effects from complex orography, which can degrade both SAR and InSAR imagery of terrain radar reflectivity and height. In this work, the problem of retrieving radar reflectivity of layover areas is addressed. It is formulated as the problem of estimating a multicomponent sinusoidal signal corrupted by multiplicative complex correlated noise and additive white Gaussian noise. Application of nonparametric [e.g., Capon, amplitude and phase estimation filter (APES)], parametric [least squares, modern parametric RELAXation spectral estimator (RELAX)], and hybrid spectral estimators for amplitude estimation is investigated for a multilook scenario. In particular, the multilook extensions of RELAX and APES are applied to the interferometric problem. Performance analysis is investigated through a Cramer-Rao lower bound calculation and Monte Carlo simulation. The method of least squares, coupled with Capon's approach to spatial frequency estimation, multilook APES, and multilook RELAX turn out to provide accurate reflectivity estimates for undistorted multibaseline image formation of layover areas.},
issn = {1053-587X},
keywords = {SAR Processing, Tomography, SAR Tomography, Multi-baseline SAR, Interferometry, SAR Interferometry, AWGN, Monte Carlo methods, amplitude estimation, radar imaging, radiowave interferometry, synthetic aperture radar APES, Capon's approach, InSAR, Monte Carlo simulation, RELAX, SAR, additive white Gaussian noise, amplitude estimation, complex orography, component sinusoidal signal, hybrid spectral estimators, layover extended sources, multibaseline interferometric radar imaging, multibaseline operation, multiplicative complex correlated noise, nonparametric estimators, parametric estimators, reflectivity estimation, spatial frequency estimation, synthetic aperture radar interferometry, terrain height, undistorted multibaseline image formation},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/lombardiniMontanariGini2003.pdf},
url = {http://ieeexplore.ieee.org/iel5/78/27018/01200140.pdf} 
}


  8. Clifford J. Nolan and Margaret Cheney. Synthetic Aperture Inversion for Arbitrary Flight Paths and Nonflat Topography. IEEE Transactions on Image Processing, 12(9):1035-1043, Sept 2003.
    Keywords: SAR Processing, Back-Projection, Backprojection, FOPEN, Non-Flat Topography, Non-Linear Flight Path.
    Abstract: This paper considers synthetic aperture radar (SAR) and other synthetic aperture imaging systems in which a backscattered wave is measured from positions along an arbitrary (known) flight path.We assume a single-scattering model for the radar data, and we assume that the ground topography is known but not necessarily flat. We focus on cases in which the antenna footprint is so large that the standard narrow-beam algorithms are not useful.We showthat certain artifacts can be avoided if the antenna and antenna footprint avoid particular relationships with the ground topography. In this case, we give an explicit backprojection imaging algorithm that corrects for the ground topography, flight path, antenna beam pattern, source waveform, and other geometrical factors. For the case of a nondirectional antenna, the image produced by the above algorithm contains artifacts. For this case, we analyze the strength of the artifacts relative to the strength of the true image. The analysis shows that the artifacts can be somewhat suppressed by increasing the frequency, integration time, and the curvature of the flight path. 

    @ARTICLE{nolan:SARInversion2,
author = {Clifford J. Nolan and Margaret Cheney},
title = {{Synthetic Aperture Inversion for Arbitrary Flight Paths and Nonflat Topography}},
journal = {IEEE Transactions on Image Processing},
year = {2003},
volume = {12},
pages = {1035-1043},
number = {9},
month = Sept,
abstract = {This paper considers synthetic aperture radar (SAR) and other synthetic aperture imaging systems in which a backscattered wave is measured from positions along an arbitrary (known) flight path.We assume a single-scattering model for the radar data, and we assume that the ground topography is known but not necessarily flat. We focus on cases in which the antenna footprint is so large that the standard narrow-beam algorithms are not useful.We showthat certain artifacts can be avoided if the antenna and antenna footprint avoid particular relationships with the ground topography. In this case, we give an explicit backprojection imaging algorithm that corrects for the ground topography, flight path, antenna beam pattern, source waveform, and other geometrical factors. For the case of a nondirectional antenna, the image produced by the above algorithm contains artifacts. For this case, we analyze the strength of the artifacts relative to the strength of the true image. The analysis shows that the artifacts can be somewhat suppressed by increasing the frequency, integration time, and the curvature of the flight path.},
keywords = {SAR Processing, Back-Projection,Backprojection, FOPEN, Non-Flat Topography, Non-Linear Flight Path},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/nolan03.pdf},
url = {www.rpi.edu/~cheney/papers/sarieeereprint.pdf} 
}


  9. Pau Prats and Jordi J. Mallorqui. Estimation of azimuth phase undulations with multisquint processing in airborne interferometric SAR images. Geoscience and Remote Sensing, IEEE Transactions on, 41(6):1530-1533, 2003.
    Keywords: SAR Processing, Squinted SAR, airborne radar, radar imaging, synthetic aperture radar, ESAR, DLR experimental airborne SAR, Germany, Oberpfaffenhofen test site, azimuth phase undulations, calibration, image pairs, interferometric airborne synthetic aperture radar systems, multisquint processing, phase error correction, phase error detection, single-pass interferometrie data, squint angles, technique, InSAR, Interferometry.
    Abstract: Presents a technique to detect and correct phase errors appearing in interferometric airborne synthetic aperture radar (SAR) systems due to the lack of precision in the navigation system. The technique is based on a multisquint processing approach, i.e. by processing the same image pairs with different squint angles we can combine the information of different interferograms to obtain the desired phase correction. Airborne single-pass interferometric data from the Deutsches Zentrum fuer Luft- und Raumfahrt (DLR) experimental airborne SAR is used to validate the method. 

    @ARTICLE{pratsMallorqui03:ESAR,
author = {Prats, Pau and Mallorqui, Jordi J.},
title = {{Estimation of azimuth phase undulations with multisquint processing in airborne interferometric SAR images}},
journal = {Geoscience and Remote Sensing, IEEE Transactions on},
year = {2003},
volume = {41},
pages = {1530-1533},
number = {6},
abstract = {Presents a technique to detect and correct phase errors appearing in interferometric airborne synthetic aperture radar (SAR) systems due to the lack of precision in the navigation system. The technique is based on a multisquint processing approach, i.e. by processing the same image pairs with different squint angles we can combine the information of different interferograms to obtain the desired phase correction. Airborne single-pass interferometric data from the Deutsches Zentrum fuer Luft- und Raumfahrt (DLR) experimental airborne SAR is used to validate the method.},
keywords = {SAR Processing, Squinted SAR,airborne radar, radar imaging, synthetic aperture radar, ESAR, DLR experimental airborne SAR, Germany, Oberpfaffenhofen test site, azimuth phase undulations, calibration, image pairs, interferometric airborne synthetic aperture radar systems, multisquint processing, phase error correction, phase error detection, single-pass interferometrie data, squint angles, technique, InSAR, Interferometry},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/pratsMallorqui03.pdf},
url = {http://ieeexplore.ieee.org/iel5/36/27418/01220264.pdf} 
}


  10. A. Reigber and R. Scheiber. Airborne differential SAR interferometry: first results at L-band. Geoscience and Remote Sensing, IEEE Transactions on, 41(6):1516--1520, 2003.
    Keywords: SAR Processing, airborne radar, radiowave interferometry, remote sensing by radar, synthetic aperture radar, vegetation mapping, Earth surface, Germany, L-Band, Oberpfaffenhofen test site, agricultural areas, airborne differential SAR interferometry, airborne sensors, atmospheric effects, centimetre-scale deformations, critical region monitoring, data acquisition intervals, forested areas, glacier flows, interferometric repeat-pass mode, landslides, long-term decorrelation, motion compensation, motion errors, phase artifacts, synthetic aperture radar, ESAR, Motion Compensation, Interferometric SAR, Interferometry, D-InSAR.
    Abstract: In recent years, differential interferometry using spaceborne synthetic aperture radar (SAR) sensors has become an established technique for detecting and monitoring centimetre-scale deformations of the Earth's surface, as well as glacier flows and landslides. Although often very efficient, the use of spaceborne SAR data has several drawbacks, namely phase artifacts caused by atmospheric effects and very low coherence due to long data acquisition intervals and the short radar wavelength of the sensor. Most important, current spaceborne sensors are not able to ensure flexible monitoring of critical regions. Airborne sensors may overcome most of the problems mentioned above, but up to now, the operational use of airborne differential SAR interferometry has been prevented by insufficiently accurate motion compensation of the platform. In this letter, first results of airborne differential interferometry using the German Aerospace Center (DLR) experimental SAR system (E-SAR) in the interferometric repeat-pass mode are addressed. This includes an analysis of long-term decorrelation behavior in L-band and, particularly, the correction of residual motion errors in heavily decorrelated interferograms. A first differential interferogram of agricultural and forested areas is presented and analyzed. 

    @ARTICLE{reigberScheiber03:DiffSARLBand,
author = {Reigber, A. and Scheiber, R.},
title = {Airborne differential SAR interferometry: first results at L-band},
journal = {Geoscience and Remote Sensing, IEEE Transactions on},
year = {2003},
volume = {41},
pages = {1516--1520},
number = {6},
abstract = {In recent years, differential interferometry using spaceborne synthetic aperture radar (SAR) sensors has become an established technique for detecting and monitoring centimetre-scale deformations of the Earth's surface, as well as glacier flows and landslides. Although often very efficient, the use of spaceborne SAR data has several drawbacks, namely phase artifacts caused by atmospheric effects and very low coherence due to long data acquisition intervals and the short radar wavelength of the sensor. Most important, current spaceborne sensors are not able to ensure flexible monitoring of critical regions. Airborne sensors may overcome most of the problems mentioned above, but up to now, the operational use of airborne differential SAR interferometry has been prevented by insufficiently accurate motion compensation of the platform. In this letter, first results of airborne differential interferometry using the German Aerospace Center (DLR) experimental SAR system (E-SAR) in the interferometric repeat-pass mode are addressed. This includes an analysis of long-term decorrelation behavior in L-band and, particularly, the correction of residual motion errors in heavily decorrelated interferograms. A first differential interferogram of agricultural and forested areas is presented and analyzed.},
keywords = {SAR Processing, airborne radar, radiowave interferometry, remote sensing by radar, synthetic aperture radar, vegetation mapping, Earth surface, Germany, L-Band, Oberpfaffenhofen test site, agricultural areas, airborne differential SAR interferometry, airborne sensors, atmospheric effects, centimetre-scale deformations, critical region monitoring, data acquisition intervals, forested areas, glacier flows, interferometric repeat-pass mode, landslides, long-term decorrelation, motion compensation, motion errors, phase artifacts, synthetic aperture radar,ESAR, Motion Compensation, Interferometric SAR, Interferometry, D-InSAR},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/reigberScheiber03.pdf},
url = {http://ieeexplore.ieee.org/iel5/36/27418/01220261.pdf} 
}


  11. Petre Stoica, Zhisong Wang, and Jian Li. Robust Capon beamforming. IEEE Signal Processing Letters, 10(6):172--175, June 2003.
    Keywords: SAR Processing, Capon, Capon Beamforming, Robust Capon beamforming, Beamforming, Spectral Estimation, array signal processing, interference suppression, signal resolution adaptive arrays, adaptive beamforming, array steering vector, interference rejection capability, resolution, signal of interest, uncertain steering vectors.
    Abstract: The Capon beamformer has better resolution and much better interference rejection capability than the standard (data-independent) beamformer, provided that the array steering vector corresponding to the signal of interest (SOI) is accurately known. However, whenever the knowledge of the SOI steering vector is imprecise (as is often the case in practice), the performance of the Capon beamformer may become worse than that of the standard beamformer. We present a natural extension of the Capon beamformer to the case of uncertain steering vectors. The proposed robust Capon beamformer can no longer be expressed in a closed form, but it can be efficiently computed. Its excellent performance is demonstrated via a number of numerical examples. 

    @ARTICLE{stoicaWangLi2003:Capon,
author = {Stoica, Petre and Zhisong Wang and Jian Li},
title = {Robust Capon beamforming},
journal = {IEEE Signal Processing Letters},
year = {2003},
volume = {10},
pages = {172--175},
number = {6},
month = {jun},
abstract = {The Capon beamformer has better resolution and much better interference rejection capability than the standard (data-independent) beamformer, provided that the array steering vector corresponding to the signal of interest (SOI) is accurately known. However, whenever the knowledge of the SOI steering vector is imprecise (as is often the case in practice), the performance of the Capon beamformer may become worse than that of the standard beamformer. We present a natural extension of the Capon beamformer to the case of uncertain steering vectors. The proposed robust Capon beamformer can no longer be expressed in a closed form, but it can be efficiently computed. Its excellent performance is demonstrated via a number of numerical examples.},
doi = {10.1109/LSP.2003.811637},
issn = {1558-2361},
keywords = {SAR Processing, Capon, Capon Beamforming, Robust Capon beamforming, Beamforming, Spectral Estimation, array signal processing, interference suppression, signal resolution adaptive arrays, adaptive beamforming, array steering vector, interference rejection capability, resolution, signal of interest, uncertain steering vectors},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/stoicaWangLi2003.pdf},
url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1198667&isnumber=26980} 
}


  12. G. Tavernier, J. P. Granier, C. Jayles, P. Sengenes, and F. Rozo. The current evolutions of the DORIS system. Advances in Space Research, 31(8):1947--1952, 2003.
    Keywords: DORIS, Orbit, Precise Orbit, Accuracy, ENVISAT, ASAR,.
    Abstract: DORIS was developed for precise orbit determination and precise positioning on Earth. Three new satellites fitted out with dual-channel second-generation receivers have been recently launched. Jason-1, ENVISAT and SPOT-5 acquired a real autonomy thanks to DIODE real time on-board orbit determination software. Today the DORIS system has built up a global network of 55 stations. In order to reach new accuracy goals for Jason-1 and ENVISAT, it was decided to improve the long-term stability of the antennas when necessary. Third-generation beacons deployed from the end of 2001 offer new features and greater reliability. The satellites relay acquired and stored data at regular intervals to SSALTO, the new DORIS mission control center. DORIS data from the different satellites are currently available in the two Data Centers and used by the International DORIS Service Analysis groups. 

    @ARTICLE{tavernierGranierJaylesSengenesRozo03:DORIS,
author = {Tavernier, G. and Granier, J. P. and Jayles, C. and Sengenes, P. and Rozo, F.},
title = {The current evolutions of the DORIS system},
journal = {Advances in Space Research},
year = {2003},
volume = {31},
pages = {1947--1952},
number = {8},
abstract = {DORIS was developed for precise orbit determination and precise positioning on Earth. Three new satellites fitted out with dual-channel second-generation receivers have been recently launched. Jason-1, ENVISAT and SPOT-5 acquired a real autonomy thanks to DIODE real time on-board orbit determination software. Today the DORIS system has built up a global network of 55 stations. In order to reach new accuracy goals for Jason-1 and ENVISAT, it was decided to improve the long-term stability of the antennas when necessary. Third-generation beacons deployed from the end of 2001 offer new features and greater reliability. The satellites relay acquired and stored data at regular intervals to SSALTO, the new DORIS mission control center. DORIS data from the different satellites are currently available in the two Data Centers and used by the International DORIS Service Analysis groups.},
keywords = {DORIS,Orbit,Precise Orbit,Accuracy,ENVISAT, ASAR,},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/tavernierGranierJaylesSengenesRozo03.pdf},
url = {http://www.sciencedirect.com/science/article/B6V3S-49WCJGJ-H/2/b721d4e63f917fc485e9ef8762e61a57} 
}


  13. Lars M. H. Ulander, Hans Hellsten, and Gunnar Stenström. Synthetic-Aperture Radar Processing Using Fast Factorized Back-Projection. IEEE Transactions on Aerospace and Electronic Systems, 39(3):760-776, July 2003.
    Keywords: SAR Processing, Fast Factorized Back-Projection, Time-Domain Back-Projection, Backprojection, Fast Back-Projection, Factorized Back-Projection, Ultra-Wideband SAR, VHF SAR, CARABAS, Airborne SAR.
    Abstract: Exact synthetic aperture radar (SAR) inversion for a linear aperture may be obtained using fast transform techniques. Alternatively, back-projection integration in time domain can also be used. This technique has the benefit of handling a general aperture geometry. In the past, however, back-projection has seldom been used due to heavy computational burden. We show that the back-projection integral can be recursively partitioned and an effective algorithm constructed based on aperture factorization. By representing images in local polar coordinates it is shown that the number of operations is drastically reduced and can be made to approach that of fast transform algorithms. The algorithm is applied to data from the airborne ultra-wideband CARABAS SAR and shown to give a reduction in processing time of two to three orders of magnitude. 

    @ARTICLE{ulanHellSten:FastBackpro,
author = {Lars M. H. Ulander and Hans Hellsten and Gunnar Stenstr{\"o}m},
title = {{Synthetic-Aperture Radar Processing Using Fast Factorized Back-Projection}},
journal = {IEEE Transactions on Aerospace and Electronic Systems},
year = {2003},
volume = {39},
pages = {760-776},
number = {3},
month = Jul,
abstract = {Exact synthetic aperture radar (SAR) inversion for a linear aperture may be obtained using fast transform techniques. Alternatively, back-projection integration in time domain can also be used. This technique has the benefit of handling a general aperture geometry. In the past, however, back-projection has seldom been used due to heavy computational burden. We show that the back-projection integral can be recursively partitioned and an effective algorithm constructed based on aperture factorization. By representing images in local polar coordinates it is shown that the number of operations is drastically reduced and can be made to approach that of fast transform algorithms. The algorithm is applied to data from the airborne ultra-wideband CARABAS SAR and shown to give a reduction in processing time of two to three orders of magnitude.},
keywords = {SAR Processing,Fast Factorized Back-Projection, Time-Domain Back-Projection, Backprojection, Fast Back-Projection, Factorized Back-Projection ,Ultra-Wideband SAR, VHF SAR, CARABAS, Airborne SAR},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/ulanderHellstenStenstrom03.pdf},
url = {http://ieeexplore.ieee.org/iel5/7/27785/01238734.pdf} 
}


Conference articles

  1. W. - M. Boerner. Recent Advances in Extra-Wide-Band Polarimetry, Interferometry and Polarimetric Interferometry in Synthetic Aperture Remote Sensing and its Applications. In IEE Proceedings - Radar, Sonar and Navigation, volume 150, pages 113-124, June 2003.
    Keywords: SAR Processing, Interferometry, Pol-InSAR, RFI Suppression, Extra-WideBand SAR, WideBand SAR.
    Abstract: The development of radar polarimetry and radar interferometry is advancing rapidly, and these novel radar technologies are revamping 'synthetic aperture radar imaging' decisively. The successive advancements are sketched beginning with the fundamental formulations and highlighting the salient points of these diverse remote sensing techniques. Whereas with radar polarimetry the textural fine-structure, target orientation and shape, symmetries and material constituents can be recovered with considerable improvements above that of standard 'amplitude-only polarisation radar'; with radar interferometry the spatial (in depth) structure can be explored. In 'polarimetric-interferometric synthetic aperture radar (POL-IN-SAR) imaging' it is possible to recover such co-registered textural plus spatial properties simultaneously. This includes the extraction of 'digital elevation maps (DEM)' from either 'fully polarimetric (scattering matrix)' or 'interferometric (dual antenna) SAR image data takes' with the additional benefit of obtaining co-registered three-dimensional 'POL-IN-DEM' information. Extra-wide-band POL-IN-SAR imaging - when applied to 'repeat-pass image overlay interferometry' - provides differential background validation and measurement, stress assessment, and environmental stress-change monitoring capabilities with hitherto unattained accuracy, which are essential tools for improved global biomass estimation and also for wetland assessment and monitoring. More recently, by applying multiple parallel repeat-pass EWB-POL-D(RP)-IN-SAR imaging along stacked (altitudinal) or displaced (horizontal) flight-lines will result in 'tomographic (multi-interferometric) polarimetric SAR stereo-imaging', including foliage- and ground-penetrating capabilities. In addition, various closely related topics of (i) acquiring additional and protecting existing spectral windows of the 'natural electromagnetic spectrum (NES)' pertinent to remote sensing; and (ii) mitigation against common 'radio frequency interference (RFI)' and intentional 'directive jamming of airborne and spaceborne POL-IN-SAR imaging platforms' are appraised. 

    @INPROCEEDINGS{Boerner03:EWB,
author = {W. - M. Boerner},
title = {{Recent Advances in Extra-Wide-Band Polarimetry, Interferometry and Polarimetric Interferometry in Synthetic Aperture Remote Sensing and its Applications}},
booktitle = {IEE Proceedings - Radar, Sonar and Navigation},
year = {2003},
volume = {150},
number = {3},
pages = {113-124},
month = Jun,
abstract = {The development of radar polarimetry and radar interferometry is advancing rapidly, and these novel radar technologies are revamping 'synthetic aperture radar imaging' decisively. The successive advancements are sketched beginning with the fundamental formulations and highlighting the salient points of these diverse remote sensing techniques. Whereas with radar polarimetry the textural fine-structure, target orientation and shape, symmetries and material constituents can be recovered with considerable improvements above that of standard 'amplitude-only polarisation radar'; with radar interferometry the spatial (in depth) structure can be explored. In 'polarimetric-interferometric synthetic aperture radar (POL-IN-SAR) imaging' it is possible to recover such co-registered textural plus spatial properties simultaneously. This includes the extraction of 'digital elevation maps (DEM)' from either 'fully polarimetric (scattering matrix)' or 'interferometric (dual antenna) SAR image data takes' with the additional benefit of obtaining co-registered three-dimensional 'POL-IN-DEM' information. Extra-wide-band POL-IN-SAR imaging - when applied to 'repeat-pass image overlay interferometry' - provides differential background validation and measurement, stress assessment, and environmental stress-change monitoring capabilities with hitherto unattained accuracy, which are essential tools for improved global biomass estimation and also for wetland assessment and monitoring. More recently, by applying multiple parallel repeat-pass EWB-POL-D(RP)-IN-SAR imaging along stacked (altitudinal) or displaced (horizontal) flight-lines will result in 'tomographic (multi-interferometric) polarimetric SAR stereo-imaging', including foliage- and ground-penetrating capabilities. In addition, various closely related topics of (i) acquiring additional and protecting existing spectral windows of the 'natural electromagnetic spectrum (NES)' pertinent to remote sensing; and (ii) mitigation against common 'radio frequency interference (RFI)' and intentional 'directive jamming of airborne and spaceborne POL-IN-SAR imaging platforms' are appraised.},
keywords = {SAR Processing, Interferometry, Pol-InSAR, RFI Suppression, Extra-WideBand SAR, WideBand SAR},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/Boerner03.pdf},
url = {http://ieeexplore.ieee.org/iel5/2198/27458/01222371.pdf} 
}


  2. H.J. Callow, M.P. Hayes, and P.T. Gough. Autofocus of stripmap SAS data using the range-variant SPGA algorithm. In OCEANS 2003. Proceedings, volume 5, pages 2422--2426Vol.5, 22-26 Sept. 2003.
    Keywords: SAR Processing, Autofocus, Phase Curvature Autofocus, Phase Gradient Autofocus, PGA, SPGA, Stripmap Phase Gradient Algorithm, Synthetic Aperture Sonar, SAS. 
    @INPROCEEDINGS{Callow2003a,
author = {Callow, H.J. and Hayes, M.P. and Gough, P.T.},
title = {Autofocus of stripmap SAS data using the range-variant SPGA algorithm},
booktitle = {OCEANS 2003. Proceedings},
year = {2003},
volume = {5},
pages = {2422--2426Vol.5},
month = {22-26 Sept.},
keywords = {SAR Processing, Autofocus, Phase Curvature Autofocus, Phase Gradient Autofocus, PGA, SPGA, Stripmap Phase Gradient Algorithm, Synthetic Aperture Sonar, SAS},
owner = {ofrey} 
}


  3. H.J. Callow, M.P. Hayes, and P.T. Gough. Stripmap phase gradient autofocus. In OCEANS 2003. Proceedings, volume 5, pages 2414--2421, September 2003.
    Keywords: SAR Processing, Autofocus, Phase Curvature Autofocus, Phase Gradient Autofocus, PGA, SPGA, Stripmap Phase Gradient Algorithm, Synthetic Aperture Sonar, SAS.
    Abstract: Current sonar autofocus techniques for blur removal originate in the radar community but have not provided a complete solution for Synthetic Aperture Sonar (SAS) imagery. The wide-beam, wide-band nature of SAS imagery makes implementation of Synthetic Aperture Radar (SAR) autofocus techniques difficult. This paper describes a generalisation of the standard Phase Gradient Antofocus (PGA) algorithm used in spotlight SAR that allows operation with stripmap SAS geometries. PGA uses prominent points within the target scene to estimate image blurring and phase errors. We show how PGA can be generalised to work with wide-band, wide-heam stripmap geometries. The SPGA method works by employing wavenumher domain 2D phase estimation techniques. The 2D phase errors are related to aperture position errors using the wavenumber transform. Robust sway estimates are obtained by using redundancy over a number of target points. We also present an improved Phase Curvature Autofocus (PCA) algorithm using the wavenumher transform. Preliminary results from the two algorithms (both on field-collected and simulated data sets) are presented and related to those obtained using previous methods. A discussion of SPGA's benefits over traditional algorithms and the limitations of the SPGA algorithm. The SPGA algorithm was found to perform better than 2-D PCA on both simulated and field-collected data sets. Further testing on a variety of target scenes and imagery is required to investigate avenues of autofoeus improvement. 

    @INPROCEEDINGS{Callow2003,
author = {Callow, H.J. and Hayes, M.P. and Gough, P.T.},
title = {Stripmap phase gradient autofocus},
booktitle = {OCEANS 2003. Proceedings},
year = {2003},
volume = {5},
pages = {2414--2421},
month = {sep},
abstract = {Current sonar autofocus techniques for blur removal originate in the radar community but have not provided a complete solution for Synthetic Aperture Sonar (SAS) imagery. The wide-beam, wide-band nature of SAS imagery makes implementation of Synthetic Aperture Radar (SAR) autofocus techniques difficult. This paper describes a generalisation of the standard Phase Gradient Antofocus (PGA) algorithm used in spotlight SAR that allows operation with stripmap SAS geometries. PGA uses prominent points within the target scene to estimate image blurring and phase errors. We show how PGA can be generalised to work with wide-band, wide-heam stripmap geometries. The SPGA method works by employing wavenumher domain 2D phase estimation techniques. The 2D phase errors are related to aperture position errors using the wavenumber transform. Robust sway estimates are obtained by using redundancy over a number of target points. We also present an improved Phase Curvature Autofocus (PCA) algorithm using the wavenumher transform. Preliminary results from the two algorithms (both on field-collected and simulated data sets) are presented and related to those obtained using previous methods. A discussion of SPGA's benefits over traditional algorithms and the limitations of the SPGA algorithm. The SPGA algorithm was found to perform better than 2-D PCA on both simulated and field-collected data sets. Further testing on a variety of target scenes and imagery is required to investigate avenues of autofoeus improvement.},
doi = {10.1109/OCEANS.2003.1282922},
keywords = {SAR Processing, Autofocus, Phase Curvature Autofocus, Phase Gradient Autofocus, PGA, SPGA, Stripmap Phase Gradient Algorithm, Synthetic Aperture Sonar, SAS},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/callowHayesGough2003.pdf} 
}


  4. Hubert-M.J. Cantalloube and Pascale Dubois-Fernandez. Airborne X-band SAR imaging with 10 cm resolution - technical challenge and preliminary results. In , volume 1, pages 185-187 vol.1, July 2003.
    Keywords: SAR Processing, Motion Compensation, Autofocus, radar cross-sections, radar imaging, radar resolution, remote sensing by radar, synthetic aperture radar 2 1/2 D surface modelling, Doppler algorithms, Ku bands, RAMSES, X-Band, X-band SAR imaging, Airborne SAR, antenna pattern compensation method, back-injection synthesis algorithm, carrier trajectory, clutter appearance, differential GPS-hybridized inertial navigation unit, high resolution clutters, isotropic echoes, matching cross-range resolution, optical surface modelling, phase tracking, point-like echoes, Range Migration Algorithm, resolution cell, synthetic aperture radar, TDBP, Time-Domain Back-Projection, temporal-domain synthesis algorithm, texture simulations, omega-k algorithm.
    Abstract: RAMSES airborne SAR system bandwith was recently increased to 1.2 GHz in X and Ku bands, yielding (unweighted) 3 dB range resolution of 11 cm. Synthesis of SAR images with matching cross-range resolution, requires long integration time thus disqualifies temporal-domain back-injection synthesis algorithm as impractically slow. The wider relative bandwidth also disqualifies simplified range/Doppler types of algorithms because the hypothesis of proportionality between Doppler and squint is no more valid. Therefore, we implemented a fast frequency-domain synthesis algorithm (Ω-k or range-migration algorithm) and designed a new deterministic motion and antenna pattern compensation method for it. Since the required accuracy on carrier trajectory exceeded the performance of our differential GPS-hybridized inertial navigation unit, we implemented an autofocus based on the phase tracking of several isotropic point-like echoes. Since the resolution cell is only a few wavelength wide, clutter appearance and statistics is unusual. We present here some typical examples for high resolution clutters and compare with texture simulations from optical 2 1/2 D surface modelling. 

    @INPROCEEDINGS{cantalloubeDuboisFernandez2003:HiResAutofocus,
author = {Cantalloube, Hubert-M.J. and Dubois-Fernandez, Pascale},
title = {{Airborne X-band SAR imaging with 10 cm resolution - technical challenge and preliminary results}},
year = {2003},
volume = {1},
pages = { 185-187 vol.1},
month = {July},
abstract = {RAMSES airborne SAR system bandwith was recently increased to 1.2 GHz in X and Ku bands, yielding (unweighted) 3 dB range resolution of 11 cm. Synthesis of SAR images with matching cross-range resolution, requires long integration time thus disqualifies temporal-domain back-injection synthesis algorithm as impractically slow. The wider relative bandwidth also disqualifies simplified range/Doppler types of algorithms because the hypothesis of proportionality between Doppler and squint is no more valid. Therefore, we implemented a fast frequency-domain synthesis algorithm (Ω-k or range-migration algorithm) and designed a new deterministic motion and antenna pattern compensation method for it. Since the required accuracy on carrier trajectory exceeded the performance of our differential GPS-hybridized inertial navigation unit, we implemented an autofocus based on the phase tracking of several isotropic point-like echoes. Since the resolution cell is only a few wavelength wide, clutter appearance and statistics is unusual. We present here some typical examples for high resolution clutters and compare with texture simulations from optical 2 1/2 D surface modelling.},
journal = {Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International},
keywords = {SAR Processing, Motion Compensation, Autofocus, radar cross-sections, radar imaging, radar resolution, remote sensing by radar, synthetic aperture radar 2 1/2 D surface modelling, Doppler algorithms, Ku bands, RAMSES, X-Band, X-band SAR imaging, Airborne SAR, antenna pattern compensation method, back-injection synthesis algorithm, carrier trajectory, clutter appearance, differential GPS-hybridized inertial navigation unit, high resolution clutters, isotropic echoes, matching cross-range resolution, optical surface modelling, phase tracking, point-like echoes, Range Migration Algorithm, resolution cell, synthetic aperture radar, TDBP, Time-Domain Back-Projection, temporal-domain synthesis algorithm, texture simulations, omega-k algorithm},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/cantalloubeDuboisFernandez2003.pdf},
url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1293718&isnumber=28601} 
}


  5. Shane R. Cloude and Konstantinos P. Papathanassiou. Three-stage inversion process for polarimetric SAR interferometry. In , volume 150, pages 125-134, June 2003.
    Keywords: SAR Processing, decorrelation, electromagnetic wave scattering, inverse problems, parameter estimation, radar imaging, radar polarimetry, remote sensing by radar, synthetic aperture radar geometrical approach, ground topography, interferograms, inversion accuracy, mean extinction estimation, model structure, multiple polarisation channels, parameter estimates, parameter estimation, polarimetric SAR interferometry, random canopy, simulated vector coherent SAR data, single frequency sensor, temporal decorrelation, three-stage inversion process, two-layer coherent scattering model, vegetation height, vertical tree structure.
    Abstract: The authors provide a new geometrical approach for the inversion of a two-layer coherent scattering model, widely used for the interpretation of polarimetric interferometric SAR data. It has been shown in several recent publications that, by using interferograms in multiple polarisation channels, estimation of vegetation height, underlying ground topography and mean extinction is possible. Furthermore, this can be achieved with a single frequency sensor without the need for a separate reference DEM, other a priori information or the use of data-specific regression formulas. The authors first review the details of this approach and then develop a three-stage inversion procedure to illustrate the steps involved in parameter estimation. They then consider several possible sources of error in the inversion. In particular, they concentrate on the effects of vertical tree structure and on the effects of temporal decorrelation on inversion accuracy. It is shown that the former leads to errors, mainly in the extinction estimation, while the latter does not change the model structure but reduces the available parameter set and increases the variance of the parameter estimates. Finally, the new algorithm is applied to simulated vector coherent SAR data for a random canopy. 

    @INPROCEEDINGS{cloudePapathanassiou2003:3StageInversionPolInSAR,
author = {Cloude, Shane R. and Papathanassiou, Konstantinos P.},
title = {Three-stage inversion process for polarimetric SAR interferometry},
year = {2003},
volume = {150},
number = {3},
pages = {125-134},
month = jun,
abstract = { The authors provide a new geometrical approach for the inversion of a two-layer coherent scattering model, widely used for the interpretation of polarimetric interferometric SAR data. It has been shown in several recent publications that, by using interferograms in multiple polarisation channels, estimation of vegetation height, underlying ground topography and mean extinction is possible. Furthermore, this can be achieved with a single frequency sensor without the need for a separate reference DEM, other a priori information or the use of data-specific regression formulas. The authors first review the details of this approach and then develop a three-stage inversion procedure to illustrate the steps involved in parameter estimation. They then consider several possible sources of error in the inversion. In particular, they concentrate on the effects of vertical tree structure and on the effects of temporal decorrelation on inversion accuracy. It is shown that the former leads to errors, mainly in the extinction estimation, while the latter does not change the model structure but reduces the available parameter set and increases the variance of the parameter estimates. Finally, the new algorithm is applied to simulated vector coherent SAR data for a random canopy.},
doi = {10.1049/ip-rsn:20030449},
issn = {1350-2395},
journal = {IEE Proceedings - Radar, Sonar and Navigation},
keywords = {SAR Processing, decorrelation, electromagnetic wave scattering, inverse problems, parameter estimation, radar imaging, radar polarimetry, remote sensing by radar, synthetic aperture radar geometrical approach, ground topography, interferograms, inversion accuracy, mean extinction estimation, model structure, multiple polarisation channels, parameter estimates, parameter estimation, polarimetric SAR interferometry, random canopy, simulated vector coherent SAR data, single frequency sensor, temporal decorrelation, three-stage inversion process, two-layer coherent scattering model, vegetation height, vertical tree structure},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/cloudePapathanassiou2003.pdf},
url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1222372&isnumber=27458} 
}


  6. C. Colesanti, A. Ferretti, C. Prati, and F. Rocca. Multi-image satellite SAR interferometry: state of the art and future trends. In Proc. Int. Radar Conf., pages 239--244, September 2003.
    Keywords: SAR Processing, InSAR, SAR Interferometry, electromagnetic wave scattering, radar imaging, remote sensing by radar, spaceborne radar, synthetic aperture radar, ground deformation data, high precision elevation data, multi-image satellite SAR interferometry, permanent scatterers technique, spaceborne interferometric SAR images, sparse privileged point-wise radar target grid, synthetic aperture radar.
    Abstract: In this paper, we wish to review briefly the principles underlying a recently developed approach, known as the permanent scatterers (PS) technique and aimed at the joint exploitation of a series of spaceborne interferometric SAR images for the retrieval of high precision elevation and ground deformation data on a sparse grid of privileged point-wise radar targets. 

    @INPROCEEDINGS{colesantiFerrettiPratiRocca2003:MBInSAR,
author = {Colesanti, C. and Ferretti, A. and Prati, C. and Rocca, F.},
title = {Multi-image satellite {SAR} interferometry: state of the art and future trends},
booktitle = {Proc. Int. Radar Conf.},
year = {2003},
pages = {239--244},
month = sep,
abstract = {In this paper, we wish to review briefly the principles underlying a recently developed approach, known as the permanent scatterers (PS) technique and aimed at the joint exploitation of a series of spaceborne interferometric SAR images for the retrieval of high precision elevation and ground deformation data on a sparse grid of privileged point-wise radar targets.},
doi = {10.1109/RADAR.2003.1278746},
issn = { },
keywords = {SAR Processing, InSAR, SAR Interferometry, electromagnetic wave scattering, radar imaging, remote sensing by radar, spaceborne radar, synthetic aperture radar, ground deformation data, high precision elevation data, multi-image satellite SAR interferometry, permanent scatterers technique, spaceborne interferometric SAR images, sparse privileged point-wise radar target grid, synthetic aperture radar},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/colesantiFerrettiPratiRocca2003.pdf},
url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1278746&isnumber=28560} 
}


  7. Ian G. Cumming, Y. L. Neo, and Frank Wong. Interpretations of the Omega-K Algorithm and Comparisons with other Algorithms. In IGARSS '03, International Geoscience and Remote Sensing Symposium, 2003.
    Keywords: SAR Processing, Range Migration Algorithm, omega-k, Wavenumber Domain Algorithm, Stolt Mapping, Chirp Scaling Algorithm, Range-Doppler Algorithm, Comparison of Algorithms.
    Abstract: This paper presents a Fourier interpretation of the Omega-k SAR processing algorithm that helps explain the key Stolt mapping operation. An approximate form of the algorithm is sometimes used, and we explain how both forms of the Omega-k compare with the range Doppler and the chirp scaling algorithms. Finally, a brief discussion is given on which radar parameters allow the accurate use of each algorithm. 

    @INPROCEEDINGS{CumNeoWong:omegaK,
author = {Ian G. Cumming and Y. L. Neo and Frank Wong},
title = {{Interpretations of the Omega-K Algorithm and Comparisons with other Algorithms}},
booktitle = {IGARSS '03, International Geoscience and Remote Sensing Symposium},
year = {2003},
abstract = {This paper presents a Fourier interpretation of the Omega-k SAR processing algorithm that helps explain the key Stolt mapping operation. An approximate form of the algorithm is sometimes used, and we explain how both forms of the Omega-k compare with the range Doppler and the chirp scaling algorithms. Finally, a brief discussion is given on which radar parameters allow the accurate use of each algorithm.},
keywords = {SAR Processing, Range Migration Algorithm, omega-k, Wavenumber Domain Algorithm, Stolt Mapping, Chirp Scaling Algorithm, Range-Doppler Algorithm, Comparison of Algorithms},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/CumNeoWong03.pdf} 
}


  8. M. De Stefano and Andrea Monti-Guarnieri. Robust Doppler Centroid estimate for ERS and ENVISAT. In Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International, volume 6, pages 4062--4064, 2003.
    Keywords: SAR Processing, Doppler Centroid Estimation, Doppler Ambiguity Resolver, DAR, ENVISAT, ERS, MLBF, RADARSAT, Wavelength Diversity, WDAR, Multilook Beat Frequency, fine polynomial estimation, higher order technique, robust Doppler centroid estimation, robustness, second order statistic estimator, unambiguous Doppler estimation.
    Abstract: The algorithm presented is capable of retrieving the correct DC ambiguity and to fit a fine polynomial estimate both on uniform and contrasted scenes. The core of the algorithm exploits a block wise processing: in each block a coarse unambiguous estimate is provided by exploiting both a second order statistic estimator (WDAR) and a higher order technique (MLBF). The final, fine estimate of the unambiguous Doppler is achieved by jointly exploiting the coarse unambiguous estimate with a fine, ambiguous one. The proposed algorithm accounts carefully for large variation of DC with range, like for recent Emergency Backup Mode of ERS and RADARSAT. The final estimate and its confidence is provided by a weighted average of the block measures. Tuning of the weights and additional check ensure robustness. The estimate of the offset frequency constant is then approached and a solution for calibrating its value is provided. 

    @INPROCEEDINGS{deStefanoMontiGuarinieri03:dopCen,
author = {De Stefano, M. and Monti-Guarnieri, Andrea},
title = {Robust Doppler Centroid estimate for ERS and ENVISAT},
booktitle = {Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International},
year = {2003},
volume = {6},
pages = {4062--4064},
abstract = {The algorithm presented is capable of retrieving the correct DC ambiguity and to fit a fine polynomial estimate both on uniform and contrasted scenes. The core of the algorithm exploits a block wise processing: in each block a coarse unambiguous estimate is provided by exploiting both a second order statistic estimator (WDAR) and a higher order technique (MLBF). The final, fine estimate of the unambiguous Doppler is achieved by jointly exploiting the coarse unambiguous estimate with a fine, ambiguous one. The proposed algorithm accounts carefully for large variation of DC with range, like for recent Emergency Backup Mode of ERS and RADARSAT. The final estimate and its confidence is provided by a weighted average of the block measures. Tuning of the weights and additional check ensure robustness. The estimate of the offset frequency constant is then approached and a solution for calibrating its value is provided.},
keywords = {SAR Processing, Doppler Centroid Estimation, Doppler Ambiguity Resolver, DAR, ENVISAT, ERS, MLBF, RADARSAT, Wavelength Diversity, WDAR, Multilook Beat Frequency, fine polynomial estimation, higher order technique, robust Doppler centroid estimation, robustness, second order statistic estimator, unambiguous Doppler estimation},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/deStefanoMontiGuarinieri03.pdf},
url = {http://ieeexplore.ieee.org/iel5/9010/28606/01295362.pdf} 
}


  9. Joachim H. G. Ender. SAR/MTI with Multi-Subaperture Phased Arrays. In Proceedings of the Tyrrhenian International Workshop on Remote Sensing TIWRS, pages 313-331, September 2003.
    Keywords: SAR, Multi-Channel SAR, MTI, AER-II, PAMIR, Subaperture Processing, Phased Array Radar, SAR Processing, Multi-Channel SAR, MTI, AER-II, PAMIR, Subaperture Processing, Phased Array Radar, Tomography, SAR Tomography.
    Abstract: SAR systems equipped with a phased array antenna and several receiver channels offer additional flexibility and extended target signatures. Besides of the electronic beam-steering permitting interesting operational modes, the partitioning into subarrays with parallel receiving channels opens the possibility to receive multichannel signals containing much more information about the scene than in the classical single channel case. In this paper, we start from a general signal model for wideband multi-channel data. This signal model serves as a basis for the development of algorithms for some special array configurations and applications. The approach is done from a signal theoretical point of view including statistical analysis. Most of the methods apply also to small groups of classical antennas, so the considerations are not limited to phased arrays. The airborne experimental multi-channel SAR systems AER and PAMIR serve as demonstrators for extended possibilities of imaging radars equipped with active phased arrays and parallel receiving channels. The presented examples have been achieved with these demonstrators.
    Comments: + Much und MTI, but topics like SAR tomography are covered as well. Anything that is multi-channel. 

    @INPROCEEDINGS{ender03:SARMTITomo,
author = {Joachim H. G. Ender},
title = {{SAR/MTI with Multi-Subaperture Phased Arrays}},
booktitle = {Proceedings of the Tyrrhenian International Workshop on Remote Sensing TIWRS},
year = {2003},
pages = {313-331},
month = sep,
abstract = {SAR systems equipped with a phased array antenna and several receiver channels offer additional flexibility and extended target signatures. Besides of the electronic beam-steering permitting interesting operational modes, the partitioning into subarrays with parallel receiving channels opens the possibility to receive multichannel signals containing much more information about the scene than in the classical single channel case. In this paper, we start from a general signal model for wideband multi-channel data. This signal model serves as a basis for the development of algorithms for some special array configurations and applications. The approach is done from a signal theoretical point of view including statistical analysis. Most of the methods apply also to small groups of classical antennas, so the considerations are not limited to phased arrays. The airborne experimental multi-channel SAR systems AER and PAMIR serve as demonstrators for extended possibilities of imaging radars equipped with active phased arrays and parallel receiving channels. The presented examples have been achieved with these demonstrators.},
comments = {+ Much und MTI, but topics like SAR tomography are covered as well. Anything that is multi-channel.},
keyword = {SAR, Multi-Channel SAR, MTI, AER-II, PAMIR, Subaperture Processing, Phased Array Radar},
keywords = {SAR Processing, Multi-Channel SAR, MTI, AER-II, PAMIR, Subaperture Processing, Phased Array Radar, Tomography, SAR Tomography},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/ender03.pdf} 
}


  10. Joachim H.G. Ender and Andreas R. Brenner. PAMIR - a wideband phased array SAR/MTI system. In IEE Proceedings - Radar, Sonar and Navigation, number 3, pages 165-172, June 2003.
    Keywords: SAR Processing, PAMIR, MTI, GMTI, Time-Domain Backprojection, Backprojection, Spotlight SAR, FGAN, X-Band, InSAR 1.8 GHz, ISAR, IfSAR, Phased Array Multifunctional Imaging Radar, X-band radar, airborne imaging radar, electronically steerable phased array, ground moving objects, ground moving target indication, ground-moving target indication, inverse SAR, long-range imaging capabilities, multichannel capability, operational modes, receive channels, reconfigurable phased array antenna, reconnaissance tasks, resolution, signal bandwidth, single-pass interferometric SAR, space-time adaptive processing, spaceborne imaging radar, subapertures, surveillance, synthetic aperture radar, wideband phased array SAR/MTI system, wideband system design.
    Abstract: Air- and spaceborne imaging radar systems in forthcoming surveillance and reconnaissance tasks have to meet increasingly severe demands. The next generation of top-level synthetic aperture radar (SAR) systems will comprise, among others, high resolution and long-range imaging capabilities, highly sensitive ground moving target indication and a multitude of sophisticated operational modes. The variety of tasks can be fulfilled only by the use of a reconfigurable phased array antenna together with a comprehensive wideband system design and a multichannel capability. At FGAN a new experimental X-band radar has been conceived, which will possess in its final upgrade an electronically steerable phased array consisting of 16 autonomous and reconfigurable subapertures, five independent receive channels, and a total signal bandwidth of about 1.8 GHz. The sensor is called PAMIR (Phased Array Multifunctional Imaging Radar). It is envisaged to demonstrate SAR imaging at a very high resolution and for a long range. The fine resolution will also be achieved with inverse SAR (ISAR) imaging of ground moving objects. Furthermore, the number of receive channels will allow ground-moving target indication (GMTI) by space?time adaptive processing and single-pass interferometric SAR (IfSAR) with a very high 3-D resolution. In its current stage of extension PAMIR is operable with one receive channel and a mechanically steerable antenna array. The system design and the intended capabilities of PAMIR are described. Ground-based and airborne experimental results concerning high-resolution SAR and ISAR imaging are also presented. 

    @INPROCEEDINGS{enderBrennerIEE2003:PAMIR,
author = {Joachim H.G. Ender and Andreas R. Brenner},
title = {PAMIR - a wideband phased array SAR/MTI system},
booktitle = {IEE Proceedings - Radar, Sonar and Navigation},
year = {2003},
number = {3},
pages = {165-172},
month = {June},
abstract = {Air- and spaceborne imaging radar systems in forthcoming surveillance and reconnaissance tasks have to meet increasingly severe demands. The next generation of top-level synthetic aperture radar (SAR) systems will comprise, among others, high resolution and long-range imaging capabilities, highly sensitive ground moving target indication and a multitude of sophisticated operational modes. The variety of tasks can be fulfilled only by the use of a reconfigurable phased array antenna together with a comprehensive wideband system design and a multichannel capability. At FGAN a new experimental X-band radar has been conceived, which will possess in its final upgrade an electronically steerable phased array consisting of 16 autonomous and reconfigurable subapertures, five independent receive channels, and a total signal bandwidth of about 1.8 GHz. The sensor is called PAMIR (Phased Array Multifunctional Imaging Radar). It is envisaged to demonstrate SAR imaging at a very high resolution and for a long range. The fine resolution will also be achieved with inverse SAR (ISAR) imaging of ground moving objects. Furthermore, the number of receive channels will allow ground-moving target indication (GMTI) by space?time adaptive processing and single-pass interferometric SAR (IfSAR) with a very high 3-D resolution. In its current stage of extension PAMIR is operable with one receive channel and a mechanically steerable antenna array. The system design and the intended capabilities of PAMIR are described. Ground-based and airborne experimental results concerning high-resolution SAR and ISAR imaging are also presented.},
keywords = {SAR Processing, PAMIR, MTI,GMTI, Time-Domain Backprojection, Backprojection, Spotlight SAR, FGAN, X-Band, InSAR 1.8 GHz, ISAR, IfSAR, Phased Array Multifunctional Imaging Radar, X-band radar, airborne imaging radar, electronically steerable phased array, ground moving objects, ground moving target indication, ground-moving target indication, inverse SAR, long-range imaging capabilities, multichannel capability, operational modes, receive channels, reconfigurable phased array antenna, reconnaissance tasks, resolution, signal bandwidth, single-pass interferometric SAR , space-time adaptive processing, spaceborne imaging radar, subapertures, surveillance, synthetic aperture radar, wideband phased array SAR/MTI system, wideband system design},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/enderBrennerIEE2003.pdf},
url = {http://ieeexplore.ieee.org/iel5/2198/27458/01222377.pdf} 
}


  11. Tuo Fu, Meiguo Gao, and Yuan He. An improved scatter selection method for phase gradient autofocus algorithm in SAR/ISAR autofocus. In Neural Networks and Signal Processing, 2003. Proceedings of the 2003 International Conference on, volume 2, pages 1054--1057Vol.2, 14-17 Dec. 2003.
    Keywords: SAR Processing, Autofocus, Phase Gradient Autofocus. 
    @INPROCEEDINGS{Fu2003,
author = {Tuo Fu and Meiguo Gao and Yuan He},
title = {An improved scatter selection method for phase gradient autofocus algorithm in SAR/ISAR autofocus},
booktitle = {Neural Networks and Signal Processing, 2003. Proceedings of the 2003 International Conference on},
year = {2003},
volume = {2},
pages = {1054--1057Vol.2},
month = {14-17 Dec.},
doi = {10.1109/ICNNSP.2003.1281050},
keywords = {SAR Processing, Autofocus, Phase Gradient Autofocus},
owner = {ofrey} 
}


  12. A. Jakobsson, F. Gini, and F. Lombardini. Layover solution in multibaseline INSAR using robust beamforming. In Signal Processing and Information Technology, 2003. ISSPIT 2003. Proceedings of the 3rd IEEE International Symposium on, pages 328--331, 14-17 Dec. 2003. 
    @INPROCEEDINGS{Jakobsson2003,
author = {Jakobsson, A. and Gini, F. and Lombardini, F.},
title = {Layover solution in multibaseline INSAR using robust beamforming},
booktitle = {Signal Processing and Information Technology, 2003. ISSPIT 2003. Proceedings of the 3rd IEEE International Symposium on},
year = {2003},
pages = {328--331},
month = {14-17 Dec.},
doi = {10.1109/ISSPIT.2003.1341125},
owner = {ofrey} 
}


  13. A. Jakobsson, F. Lombardini, and F. Gini. Weighted subspace fitting of interferometric phases for multibaseline SAR interferometry. In Signal Processing and Its Applications, 2003. Proceedings. Seventh International Symposium on, volume 1, pages 321--324vol.1, 1-4 July 2003. 
    @INPROCEEDINGS{Jakobsson2003a,
author = {Jakobsson, A. and Lombardini, F. and Gini, F.},
title = {Weighted subspace fitting of interferometric phases for multibaseline SAR interferometry},
booktitle = {Signal Processing and Its Applications, 2003. Proceedings. Seventh International Symposium on},
year = {2003},
volume = {1},
pages = {321--324vol.1},
month = {1-4 July},
doi = {10.1109/ISSPA.2003.1224705},
owner = {ofrey} 
}


  14. J.S. Lee, D.L. Schuler, T.L. Ainsworth, and W.-M. Boerner. Polarization orientation estimation and applications: a review. In IEEE International Geoscience and Remote Sensing Symposium, 2003. IGARSS '03., volume 1, pages 428--430, July 2003.
    Keywords: SAR Processsing, calibration, covariance matrices, data acquisition, radar polarimetry, remote sensing by radar, spaceborne radar, synthetic aperture radar, terrain mapping DEM generation, AIRSAR, L-band, polarimetric SAR images, P-band, polarimetric SAR images, SIR-C, circular polarization covariance matrix, estimation algorithms, ocean surface feature characterization, polarimetric SAR data compensation, polarimetric calibration, polarization orientation angle shifts, polarization orientation estimation, radar frequency, scattering media, terrain slopes, Airborne SAR.
    Abstract: We review estimation algorithms and applications of polarization orientation angle shifts induced by terrain slopes. We develop a unified analysis of estimation algorithms based on circular polarization covariance matrix. The effect of radar frequency, scattering media, and polarimetric calibration will also be discussed. Applications to DEM generation, polarimetric SAR data compensation and ocean surface feature characterization will be mentioned. SIR-C, and JPL AIRSAR L-band and P-band polarimetric SAR images are used for demonstration. 

    @INPROCEEDINGS{leeSchulerAinsworthBoerner2003:PolSAR,
author = {Lee, J.S. and Schuler, D.L. and Ainsworth, T.L. and Boerner, W.-M.},
title = {Polarization orientation estimation and applications: a review},
booktitle = {IEEE International Geoscience and Remote Sensing Symposium, 2003. IGARSS '03.},
year = {2003},
volume = {1},
pages = {428--430},
month = {jul},
abstract = {We review estimation algorithms and applications of polarization orientation angle shifts induced by terrain slopes. We develop a unified analysis of estimation algorithms based on circular polarization covariance matrix. The effect of radar frequency, scattering media, and polarimetric calibration will also be discussed. Applications to DEM generation, polarimetric SAR data compensation and ocean surface feature characterization will be mentioned. SIR-C, and JPL AIRSAR L-band and P-band polarimetric SAR images are used for demonstration.},
keywords = {SAR Processsing, calibration, covariance matrices, data acquisition, radar polarimetry, remote sensing by radar, spaceborne radar, synthetic aperture radar, terrain mapping DEM generation,AIRSAR, L-band, polarimetric SAR images, P-band, polarimetric SAR images, SIR-C, circular polarization covariance matrix, estimation algorithms, ocean surface feature characterization, polarimetric SAR data compensation, polarimetric calibration, polarization orientation angle shifts, polarization orientation estimation, radar frequency, scattering media, terrain slopes, Airborne SAR},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/leeSchulerAinsworthBoerner2003.pdf},
url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1293798&isnumber=28601} 
}


  15. F. Lombardini. Differential tomography: a new framework for SAR interferometry. In Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International, volume 2, pages 1206--1208vol.2, 21-25 July 2003. 
    @INPROCEEDINGS{Lombardini2003,
author = {Lombardini, F.},
title = {Differential tomography: a new framework for SAR interferometry},
booktitle = {Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International},
year = {2003},
volume = {2},
pages = {1206--1208vol.2},
month = {21-25 July},
doi = {10.1109/IGARSS.2003.1294059},
owner = {ofrey},
timestamp = {2009.07.01} 
}


  16. F. Lombardini and F. Gini. Multiple reflectivities estimation for multibaseline InSAR imaging of layover extended sources. In Radar Conference, 2003. Proceedings of the International, pages 257--263, 3-5 Sept. 2003. 
    @INPROCEEDINGS{Lombardini2003b,
author = {Lombardini, F. and Gini, F.},
title = {Multiple reflectivities estimation for multibaseline InSAR imaging of layover extended sources},
booktitle = {Radar Conference, 2003. Proceedings of the International},
year = {2003},
pages = {257--263},
month = {3-5 Sept.},
doi = {10.1109/RADAR.2003.1278749},
owner = {ofrey} 
}


  17. Fabrizio Lombardini and Andreas Reigber. Adaptive spectral estimation for multibaseline SAR tomography with airborne L-band data. In IEEE International Geoscience and Remote Sensing Symposium, IGARSS '03., volume 3, pages 2014--2016, 2003.
    Keywords: SAR Processing, Tomography, SAR Tomography, Capon spectral estimator, adaptive Capon spectral estimator, spectral estimation, multibaseline 3D SAR focusing, multi-baseline SAR, InSAR, Multibaseline InSAR, Forestry.
    Abstract: In the recent years there has been growing interest in exploiting multibaseline (MB) SAR interferometry in a tomographic framework, to produce full 3D imaging e.g. of forest layers. However, Fourier-based MB SAR tomography is generally affected by unsatisfactory imaging quality due to a typically low number of baselines and their irregular distribution. In this work, we apply the more modern adaptive Capon spectral estimator to the vertical image reconstruction problem, using real airborne MB data. A first demonstration of possible imaging enhancement in real-world conditions is given. 

    @INPROCEEDINGS{lombardiniReigber03:TomoCapon,
author = {Lombardini, Fabrizio and Reigber, Andreas},
title = {{Adaptive spectral estimation for multibaseline SAR tomography with airborne L-band data}},
booktitle = {IEEE International Geoscience and Remote Sensing Symposium, IGARSS '03.},
year = {2003},
volume = {3},
pages = {2014--2016},
abstract = {In the recent years there has been growing interest in exploiting multibaseline (MB) SAR interferometry in a tomographic framework, to produce full 3D imaging e.g. of forest layers. However, Fourier-based MB SAR tomography is generally affected by unsatisfactory imaging quality due to a typically low number of baselines and their irregular distribution. In this work, we apply the more modern adaptive Capon spectral estimator to the vertical image reconstruction problem, using real airborne MB data. A first demonstration of possible imaging enhancement in real-world conditions is given.},
keywords = {SAR Processing, Tomography, SAR Tomography, Capon spectral estimator, adaptive Capon spectral estimator, spectral estimation, multibaseline 3D SAR focusing, multi-baseline SAR, InSAR,Multibaseline InSAR, Forestry},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/lombardiniReigber03.pdf},
url = {http://ieeexplore.ieee.org/iel5/9010/28603/01294324.pdf} 
}


  18. A. Löw and W. Mauser. Generation of geometrically and radiometrically terrain corrected ScanSAR images. In IEEE International Geoscience and Remote Sensing Symposium, 2003. IGARSS '03, volume 6, pages 3995-3997, 2003.
    Keywords: SAR Processing, SAR Geocoding, Radiometric Calibration, Calibration, Radiometric Correction, backscatter, microwave imaging, radiometry, synthetic aperture radar, terrain mapping, topography (Earth), ENVISAT, ASAR, RADARSAT, biophysical parameters, geometrically terrain corrected ScanSAR images, ScanSAR, geophysical parameters, microwave imagery, quantitative image analysis, radiometrically terrain corrected ScanSAR images, surface topography, synthetic aperture imagery.
    Abstract: Inclined surface topography diminishes the geometric and radiometric quality of synthetic aperture imagery. The correction of these effects becomes indispensable when quantitative image analysis is performed with respect to the derivation of geo- and biophysical parameters. Due to their spatial extent and frequent availability, ScanSAR image products extend the operative range of microwave imagery and have a high potential for numerous operational applications over larger areas. The study presents a procedure for a pre-operational terrain correction of ScanSAR imagery as acquired by RADARSAT and ENVISAT ASAR. 

    @INPROCEEDINGS{loewMauser03:RadiometricCalibration,
author = {L{\"o}w, A. and Mauser, W.},
title = {Generation of geometrically and radiometrically terrain corrected ScanSAR images},
booktitle = {IEEE International Geoscience and Remote Sensing Symposium, 2003. IGARSS '03},
year = {2003},
volume = {6},
pages = {3995-3997},
abstract = {Inclined surface topography diminishes the geometric and radiometric quality of synthetic aperture imagery. The correction of these effects becomes indispensable when quantitative image analysis is performed with respect to the derivation of geo- and biophysical parameters. Due to their spatial extent and frequent availability, ScanSAR image products extend the operative range of microwave imagery and have a high potential for numerous operational applications over larger areas. The study presents a procedure for a pre-operational terrain correction of ScanSAR imagery as acquired by RADARSAT and ENVISAT ASAR.},
keywords = {SAR Processing, SAR Geocoding, Radiometric Calibration, Calibration,Radiometric Correction, backscatter, microwave imaging, radiometry, synthetic aperture radar, terrain mapping, topography (Earth), ENVISAT, ASAR, RADARSAT, biophysical parameters, geometrically terrain corrected ScanSAR images, ScanSAR, geophysical parameters, microwave imagery, quantitative image analysis, radiometrically terrain corrected ScanSAR images, surface topography, synthetic aperture imagery},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/loewMauser03.pdf},
url = {http://ieeexplore.ieee.org/iel5/9010/28606/01295340.pdf} 
}


  19. P. Prats, J.J. Mallorqui, and A. Broquetas. Calibration of interferometric airborne SAR images using a multisquint processing approach. In Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International, volume 7, pages 4353--4355vol.7, 21-25 July 2003.
    Keywords: SAR Processing, Motion Compensation, ESAR, L-Band, X-Band, Airborne SAR, Squinted SAR, Interferometry, azimuth phase undulations, calibration, image pairs, interferometric airborne synthetic aperture radar systems, InSAR, multisquint processing, phase error correction, phase error detection, single-pass interferometrie data. 
    @INPROCEEDINGS{PratsMallorquiBroquetas2003a:MoComp,
author = {Prats, P. and Mallorqui, J.J. and Broquetas, A.},
title = {Calibration of interferometric airborne SAR images using a multisquint processing approach},
booktitle = {Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International},
year = {2003},
volume = {7},
pages = {4353--4355vol.7},
month = {21-25 July},
keywords = {SAR Processing, Motion Compensation, ESAR, L-Band, X-Band, Airborne SAR, Squinted SAR,Interferometry, azimuth phase undulations, calibration, image pairs, interferometric airborne synthetic aperture radar systems, InSAR, multisquint processing, phase error correction, phase error detection, single-pass interferometrie data},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/PratsMallorquiBroquetas2003a.pdf},
url = {http://ieeexplore.ieee.org/iel5/9010/28607/01295513.pdf} 
}


  20. A. Reigber, A. Potsis, E. Alivizatos, N. Uzunoglu, and A. Moreira. Wavenumber domain SAR focusing with integrated motion compensation. In Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International, volume 3, pages 1465--1467, 2003.
    Keywords: SAR Processing, omega-k, Range Migration Algorithm, Wavenumber Domain Algorithm, Extended omega-k, Extended Wavenumber Domain Algorithm, Motion Compensation, Squinted SAR, Airborne SAR.
    Abstract: In this paper a new SAR data processing algorithm denoted with Extended Omega-K (EOK) is analytically presented and formulated. EOK algorithm combines the advantages of the high accurate focusing of the wavenumber domain algorithms with high precision motion compensation. The new EOK algorithm integrates a two-step range adaptive motion compensation correction in the general formulation of the wavenumber domain algorithm, leading to a new SAR processing scheme, which is much more robust concerning long synthetic apertures and squint angle than for example the chirp-scaling method. Additionally it offers the possibility of processing wideband low-frequency airborne SAR data up to near-wavelength resolution. The performance and the accuracy of the new EOK SAR data processing algorithm is demonstrated using simulated data. 

    @INPROCEEDINGS{reigberPotsisAlivizatosUzunogluMoreira03:ExtendedOmegaK,
author = {Reigber, A. and Potsis, A. and Alivizatos, E. and Uzunoglu, N. and Moreira, A.},
title = {Wavenumber domain SAR focusing with integrated motion compensation},
booktitle = {Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International},
year = {2003},
volume = {3},
pages = {1465--1467},
abstract = {In this paper a new SAR data processing algorithm 

denoted with Extended Omega-K (EOK) is analytically presented 

and formulated. EOK algorithm combines the advantages of the 

high accurate focusing of the wavenumber domain algorithms 

with high precision motion compensation. The new EOK algorithm 

integrates a two-step range adaptive motion compensation 

correction in the general formulation of the wavenumber domain 

algorithm, leading to a new SAR processing scheme, which is 

much more robust concerning long synthetic apertures and squint 

angle than for example the chirp-scaling method. Additionally 

it offers the possibility of processing wideband low-frequency 

airborne SAR data up to near-wavelength resolution. 

The performance and the accuracy of the new EOK SAR data 

processing algorithm is demonstrated using simulated data.},
keywords = {SAR Processing, omega-k, Range Migration Algorithm, Wavenumber Domain Algorithm, Extended omega-k, Extended Wavenumber Domain Algorithm, Motion Compensation, Squinted SAR, Airborne SAR},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/reigberPotsisAlivizatosUzunogluMoreira03.pdf},
url = {http://ieeexplore.ieee.org/iel5/9010/28603/01294145.pdf} 
}


  21. A. Reigber, P. Prats, R. Scheiber, and J.J. Mallorqui. Options for high-precision motion compensation for airborne differential SAR interferometry. In Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International, volume 7, pages 4356--4358vol.7, 21-25 July 2003.
    Keywords: SAR Processing, D-InSAR, InSAR, ESAR, Airborne SAR, L-Band, differential interferometry, Interferometry, Motion Compensation, RME, Residual Motion Errors, Spectral Diversity, Multi-Squint Processing, Digital Elevation Model, DEM. 
    @INPROCEEDINGS{ReigberPratsScheiberMallorqui2003:MoComp,
author = {Reigber, A. and Prats, P. and Scheiber, R. and Mallorqui, J.J.},
title = {Options for high-precision motion compensation for airborne differential SAR interferometry},
booktitle = {Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International},
year = {2003},
volume = {7},
pages = {4356--4358vol.7},
month = {21-25 July},
keywords = {SAR Processing, D-InSAR, InSAR, ESAR, Airborne SAR, L-Band, differential interferometry, Interferometry, Motion Compensation, RME, Residual Motion Errors, 

Spectral Diversity, Multi-Squint Processing, Digital Elevation Model, DEM},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/ReigberPratsScheiberMallorqui2003.pdf},
url = {http://ieeexplore.ieee.org/iel5/9010/28607/01295514.pdf} 
}


  22. M. Rombach and João Moreira. Description and applications of the multipolarized dual band OrbiSAR-1 InSAR sensor. In Radar Conference, 2003. Proceedings of the International, volume 5, pages 245--250, 2003.
    Keywords: electromagnetic wave reflection, electromagnetic wave scattering, radar polarimetry, remote sensing by radar, Spaceborne SAR, synthetic aperture radar, terrain mapping, topography (Earth), vegetation mapping, OrbiSAR-1 InSAR sensor, area mapping, bald earth height information, biomass, canopy top foliage scattering, digital elevation, forest-classification, ground elevation, interferometric SAR, multipolarized dual band InSAR sensor, permanent cloud covered tropical areas, soil reflection, surface elevation, topographic maps, trunk reflection, vegetation density, vegetation height, vegetation/microwave interaction.
    Abstract: In the last decade, interferometric SAR (InSAR) has reached a wide acceptance as being a suitable tool to generate high-precision digital elevation models. Especially in tropical areas, with nearly permanent cloud coverage, InSAR provides a cost-efficient means for mapping large areas in short time periods. However, the interaction of microwaves with vegetation is strongly dependant on their frequency, demanding a careful interpretation of the extracted information. Short waves like X-band are mainly scattered back from the top of the canopy, whereas P-band penetrates the foliage and gets reflected from trunk and soil, thus carrying the phase information (and therefore the height information as well) from bald earth. For the generation of topographic maps, generally the ground elevation rather than the surface elevation is required, whereas the surface and ground elevation together enable the estimation of additional physical parameters like vegetation height, density, or biomass. 

    @INPROCEEDINGS{RombachMoreira03:OrbiSAR,
author = {Rombach, M. and Jo{\~a}o Moreira},
title = {Description and applications of the multipolarized dual band OrbiSAR-1 InSAR sensor},
booktitle = {Radar Conference, 2003. Proceedings of the International},
year = {2003},
volume = {5},
pages = {245--250},
abstract = {In the last decade, interferometric SAR (InSAR) has reached a wide acceptance as being a suitable tool to generate high-precision digital elevation models. Especially in tropical areas, with nearly permanent cloud coverage, InSAR provides a cost-efficient means for mapping large areas in short time periods. However, the interaction of microwaves with vegetation is strongly dependant on their frequency, demanding a careful interpretation of the extracted information. Short waves like X-band are mainly scattered back from the top of the canopy, whereas P-band penetrates the foliage and gets reflected from trunk and soil, thus carrying the phase information (and therefore the height information as well) from bald earth. For the generation of topographic maps, generally the ground elevation rather than the surface elevation is required, whereas the surface and ground elevation together enable the estimation of additional physical parameters like vegetation height, density, or biomass.},
keywords = {electromagnetic wave reflection, electromagnetic wave scattering, radar polarimetry, remote sensing by radar, Spaceborne SAR, synthetic aperture radar, terrain mapping, topography (Earth), vegetation mapping, OrbiSAR-1 InSAR sensor, area mapping, bald earth height information, biomass, canopy top foliage scattering, digital elevation, forest-classification, ground elevation, interferometric SAR, multipolarized dual band InSAR sensor, permanent cloud covered tropical areas, soil reflection, surface elevation, topographic maps, trunk reflection, vegetation density, vegetation height, vegetation/microwave interaction},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/RombachMoreira03.pdf},
url = {http://ieeexplore.ieee.org/iel5/9000/28560/01278747.pdf} 
}


  23. R. Scheiber. A three-step phase correction approach for airborne repeat-pass interferometric SAR data. In Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International, volume 2, pages 1190--1192vol.2, 21-25 July 2003. 
    @INPROCEEDINGS{Scheiber2003,
author = {Scheiber, R.},
title = {A three-step phase correction approach for airborne repeat-pass interferometric SAR data},
booktitle = {Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International},
year = {2003},
volume = {2},
pages = {1190--1192vol.2},
month = {21-25 July},
doi = {10.1109/IGARSS.2003.1294054},
owner = {ofrey},
timestamp = {2009.07.01} 
}


  24. David Small, Jürgen Holzner, Hannes Raggam, Detlef Kosmann, and Adrian Schubert. Geometric performance of ENVISAT ASAR products. In IGARSS '03, International Geoscience and Remote Sensing Symposium, volume 2, pages 1121--1123, 2003.
    Keywords: SAR Processing, SAR Geocoding, Geocoding, synthetic aperture radar, terrain mapping, topography (Earth), ASAR geolocation accuracy, ASAR images, ASAR slant range products, DEM, ENVISAT, ASAR, ENVISAT ASAR products, ESA, alternating polarization, corner reflectors, derivative geocoded products, ellipsoid-geocoded products, estimation techniques, geometric performance, ground control points, ground range precision, ground range products, ground range transformation, map features, medium resolution products, multiple validation, nominally geocoded GTC locations, radar geometry image products, radar image, single look complex, topographic maps, transponders, wide swath mode acquisitions, zero-Doppler iteration.
    Abstract: We describe validation measurements of the geometric accuracy of ASAR images, measured redundantly via independent methods. Our tests include image (IM), alternating polarization (AP), and wide swath (WS) mode acquisitions over a variety of test sites. ASAR's slant range products (IMS/APS) require a slightly different validation methodology than ground range precision (IMP, APP) and medium resolution products (IMM, APM, WSM). A third approach is required for ellipsoid-geocoded products (IMG, APG). The most highly accurate validation is possible with single look complex (SLC) data (IMS and APS products), as all other product types lose resolution during multilooking. For a library of ground control points (GCPs) including map features such as bridges or road intersections, as well as (where available) transponders and corner reflectors, we use surveyed or map-measured position information (together with the delay value in the case of transponders) to solve the zero-Doppler iteration and predict the position of the GCP as an azimuth and slant range coordinate in the radar image. In the case of ground range products (e.g. IMP, APP, IMM, APM, WSM) the predicted slant range value is additionally transformed by a slant to ground range transformation tro determine the predicted image coordinate. The GCP feature is then either measured by inspection of a detected image, or localized automatically within the neighborhood of the prediction. GCPs are measured within the radar geometry image products, derivative geocoded products, and topographic maps, providing their measured map, radar geometry, and nominally geocoded GTC locations. Radar image locations are compared to map reference values and statistics of differences are tabulated. We compare the accuracies of the estimates achievable using transponders and map GCPs. Based on the suite of products (and accompanying orbit information) available to us, we establish a methodology for estimating a preliminary sampling window start time bias. The multiple validation and estimation techniques used ensure robust determination of ASAR geolocation accuracy. 

    @INPROCEEDINGS{smallHolznerRaggamKosmannSchubert03:ASARGeometricPerformance,
author = {David Small and J{\"u}rgen Holzner and Hannes Raggam and Detlef Kosmann and Adrian Schubert},
title = {{Geometric performance of ENVISAT ASAR products}},
booktitle = {IGARSS '03, International Geoscience and Remote Sensing Symposium},
year = {2003},
volume = {2},
pages = {1121--1123},
abstract = {We describe validation measurements of the geometric accuracy of ASAR images, measured redundantly via independent methods. Our tests include image (IM), alternating polarization (AP), and wide swath (WS) mode acquisitions over a variety of test sites. ASAR's slant range products (IMS/APS) require a slightly different validation methodology than ground range precision (IMP, APP) and medium resolution products (IMM, APM, WSM). A third approach is required for ellipsoid-geocoded products (IMG, APG). The most highly accurate validation is possible with single look complex (SLC) data (IMS and APS products), as all other product types lose resolution during multilooking. For a library of ground control points (GCPs) including map features such as bridges or road intersections, as well as (where available) transponders and corner reflectors, we use surveyed or map-measured position information (together with the delay value in the case of transponders) to solve the zero-Doppler iteration and predict the position of the GCP as an azimuth and slant range coordinate in the radar image. In the case of ground range products (e.g. IMP, APP, IMM, APM, WSM) the predicted slant range value is additionally transformed by a slant to ground range transformation tro determine the predicted image coordinate. The GCP feature is then either measured by inspection of a detected image, or localized automatically within the neighborhood of the prediction. GCPs are measured within the radar geometry image products, derivative geocoded products, and topographic maps, providing their measured map, radar geometry, and nominally geocoded GTC locations. Radar image locations are compared to map reference values and statistics of differences are tabulated. We compare the accuracies of the estimates achievable using transponders and map GCPs. Based on the suite of products (and accompanying orbit information) available to us, we establish a methodology for estimating a preliminary sampling window start time bias. The multiple validation and estimation techniques used ensure robust determination of ASAR geolocation accuracy.},
keywords = {SAR Processing, SAR Geocoding, Geocoding, synthetic aperture radar, terrain mapping, topography (Earth), ASAR geolocation accuracy, ASAR images, ASAR slant range products, DEM,ENVISAT, ASAR, ENVISAT ASAR products, ESA, alternating polarization, corner reflectors, derivative geocoded products, ellipsoid-geocoded products, estimation techniques, geometric performance, ground control points, ground range precision, ground range products, ground range transformation, map features, medium resolution products, multiple validation, nominally geocoded GTC locations, radar geometry image products, radar image, single look complex, topographic maps, transponders, wide swath mode acquisitions, zero-Doppler iteration},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/smallHolznerRaggamKosmannSchubert03.pdf},
url = {http://ieeexplore.ieee.org/iel5/9010/28602/01294031.pdf} 
}


  25. Gordon C. Staples and Joost van der Sanden. RADARSAT-2 Polarimetry Applications. In Anais XI SBSR, Simposio Brasileiro de Sensoriamento Remoto 2003, INPE, Belo Horizonte, Brasil, volume 1, pages 2383-2389, 2003.
    Keywords: Radarsat-2, Polarimetry, Applications.
    Abstract: RADARSAT-2, planned for a mid 2004 launch, is an advanced polarimetric SAR satellite. Key features of RADARSAT-2 are high resolution (3 m), polarimetric modes, enhanced ground system providing rapid satellite tasking and near-real time data processing, improved image location accuracy, and on-board solid state recorders. The focus of this paper is on the RADARSAT-2 polarimetric applications including agriculture, cartography, disaster management, forestry, geology, hydrology, oceans, and sea ice. 

    @INPROCEEDINGS{staples:radsat2pol,
author = {Gordon C. Staples and Joost van der Sanden},
title = {{RADARSAT-2 Polarimetry Applications}},
booktitle = {Anais XI SBSR, Simposio Brasileiro de Sensoriamento Remoto 2003, INPE, Belo Horizonte, Brasil},
year = {2003},
volume = {1},
pages = {2383-2389},
abstract = {RADARSAT-2, planned for a mid 2004 launch, is an advanced polarimetric SAR satellite. Key features of RADARSAT-2 are high resolution (3 m), polarimetric modes, enhanced ground system providing rapid satellite tasking and near-real time data processing, improved image location accuracy, and on-board solid state recorders. The focus of this paper is on the RADARSAT-2 polarimetric applications including agriculture, cartography, disaster management, forestry, geology, hydrology, oceans, and sea ice.},
keywords = {Radarsat-2, Polarimetry, Applications},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/staples03.pdf},
url = {http://lagavulin.ltid.inpe.br:1905/col/ltid.inpe.br/sbsr/2003/03.27.11.57/doc/17_471.PDF} 
}


  26. B. Subiza, E. Gimeno-Nieves, J.M. Lopez-Sanchez, and J. Fortuny-Guasch. An Approach to SAR Imaging by Means of Non-Uniform FFTs. In IEEE International Geoscience and Remote Sensing Symposium, 2003. IGARSS '03., volume 6, pages 4089--4091, July 2003.
    Keywords: SAR Processing, Range Migration Algorithm, RMA, omega-k, NUFFT, Non-Uniform Fast Fourier Transform, Fast Fourier Transform, FFT, geophysical techniques, interpolation, radar imaging, synthetic aperture radar, SAR imaging algorithm, Stolt interpolation, computation time, computational efficiency, numerical simulations, seismic migration SAR processing.
    Abstract: In this study, the potential use of the non-uniform FFT (NUFFT) in SAR imaging is analyzed. The main objective has been the improvement of the computational efficiency and image accuracy of seismic migration SAR processing. Different NUFFT methods have been implemented and tested in order to choose an adequate technique for the imaging problem. Our approach consists in substituting both the Stolt interpolation and the final range inverse FFT, in the omega-k algorithm, by a single NUFFT. Numerical simulations illustrate the performance of the new method and the influence of the selection of NUFFT parameters in the precision and computation time of the SAR imaging algorithm. 

    @INPROCEEDINGS{subizaGimenoNievesLopezSanchezFortunyGuasch2003:NUFFT,
author = {Subiza, B. and Gimeno-Nieves, E. and Lopez-Sanchez, J.M. and Fortuny-Guasch, J.},
title = {An Approach to SAR Imaging by Means of Non-Uniform FFTs},
booktitle = {IEEE International Geoscience and Remote Sensing Symposium, 2003. IGARSS '03.},
year = {2003},
volume = {6},
pages = {4089--4091},
month = {jul},
abstract = {In this study, the potential use of the non-uniform FFT (NUFFT) in SAR imaging is analyzed. The main objective has been the improvement of the computational efficiency and image accuracy of seismic migration SAR processing. Different NUFFT methods have been implemented and tested in order to choose an adequate technique for the imaging problem. Our approach consists in substituting both the Stolt interpolation and the final range inverse FFT, in the omega-k algorithm, by a single NUFFT. Numerical simulations illustrate the performance of the new method and the influence of the selection of NUFFT parameters in the precision and computation time of the SAR imaging algorithm.},
doi = {10.1109/IGARSS.2003.1295371},
keywords = {SAR Processing, Range Migration Algorithm, RMA, omega-k, NUFFT,Non-Uniform Fast Fourier Transform, Fast Fourier Transform, FFT, geophysical techniques, interpolation, radar imaging, synthetic aperture radar, SAR imaging algorithm, Stolt interpolation, computation time, computational efficiency, numerical simulations, seismic migration SAR processing},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/subizaGimenoNievesLopezSanchezFortunyGuasch2003.pdf},
url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1295371&isnumber=28606} 
}


  27. T.J. Sutton, H.D. Griffiths, S.A. Chapman, R. Crook, and M. Way. Optimizing a three-stage autofocus system for synthetic aperture imaging using a UUV. In OCEANS 2003. Proceedings, volume 5, pages 2433--2437Vol.5, 22-26 Sept. 2003. 
    @INPROCEEDINGS{Sutton2003a,
author = {Sutton, T.J. and Griffiths, H.D. and Chapman, S.A. and Crook, R. and Way, M.},
title = {Optimizing a three-stage autofocus system for synthetic aperture imaging using a UUV},
booktitle = {OCEANS 2003. Proceedings},
year = {2003},
volume = {5},
pages = {2433--2437Vol.5},
month = {22-26 Sept.},
owner = {ofrey},
timestamp = {2007.06.13} 
}


  28. T.J. Sutton, H.D. Griffiths, A.P. Hetet, Y. Perrot, and S.A. Chapman. Experimental validation of autofocus algorithms for high-resolution imaging of the seabed using synthetic aperture sonar. In Radar, Sonar and Navigation, IEE Proceedings -, volume 150, pages 78--83, April 2003. 
    @INPROCEEDINGS{Sutton2003,
author = {Sutton, T.J. and Griffiths, H.D. and Hetet, A.P. and Perrot, Y. and Chapman, S.A.},
title = {Experimental validation of autofocus algorithms for high-resolution imaging of the seabed using synthetic aperture sonar},
booktitle = {Radar, Sonar and Navigation, IEE Proceedings -},
year = {2003},
volume = {150},
number = {2},
pages = {78--83},
month = {April},
doi = {10.1049/ip-rsn:20030213},
owner = {ofrey},
timestamp = {2007.06.13} 
}


  29. L. R. Varshney and D. Thomas. Sidelobe reduction for matched filter range processing. In Proc. IEEE Radar Conf., pages 446 - 451, 5-8 2003.
    Keywords: SAR Processing, Apodization, Spatially Variant Apodization, Dual Apodization, leakage energy minimization, linear frequency modulation, matched filtering, nonlinear frequency modulation, pulse compression ratio, range sidelobes, sidelobe control, sidelobe reduction, chirp modulation, frequency modulation, matched filters, minimisation, nonlinear filters, radar detection, radar interference, radar signal processing.
    Abstract: Linear frequency modulation (LFM) matched filtering results in range sidelobes. These sidelobes are often objectionable because they may mask small targets or may be mistaken for targets themselves. Various methods of sidelobe control are investigated and their performance is measured. The methods of sidelobe reduction include dual apodization, spatially variant apodization, and leakage energy minimization. Nonlinear frequency modulation (NLFM) matched filtering is also investigated. A simulation was run to compare LFM with sidelobe control and NLFM, all using moderately low pulse compression ratios. Results suggest that generally, NLFM matched filtering has better detection and estimation characteristics than LFM with sidelobe control. 

    @INPROCEEDINGS{varshneyThomas2003:Apodization,
author = {Varshney, L. R. and Thomas, D.},
title = {Sidelobe reduction for matched filter range processing},
booktitle = {Proc. IEEE Radar Conf.},
year = {2003},
pages = { 446 - 451},
month = {5-8},
abstract = { Linear frequency modulation (LFM) matched filtering results in range sidelobes. These sidelobes are often objectionable because they may mask small targets or may be mistaken for targets themselves. Various methods of sidelobe control are investigated and their performance is measured. The methods of sidelobe reduction include dual apodization, spatially variant apodization, and leakage energy minimization. Nonlinear frequency modulation (NLFM) matched filtering is also investigated. A simulation was run to compare LFM with sidelobe control and NLFM, all using moderately low pulse compression ratios. Results suggest that generally, NLFM matched filtering has better detection and estimation characteristics than LFM with sidelobe control.},
doi = {10.1109/NRC.2003.1203439},
issn = {1097-5659 },
keywords = {SAR Processing, Apodization, Spatially Variant Apodization, Dual Apodization, leakage energy minimization, linear frequency modulation, matched filtering, nonlinear frequency modulation, pulse compression ratio, range sidelobes, sidelobe control, sidelobe reduction, chirp modulation, frequency modulation, matched filters, minimisation, nonlinear filters, radar detection, radar interference, radar signal processing} 
}


  30. David A. Yocky and Charles V. Jakowatz. Automated wide-angle SAR stereo height extraction in rugged terrain using shift-scaling correlation. In Andrew G. Tescher, editor, , volume 5203, pages 10-20, 2003. SPIE.
    Keywords: SAR Processing, Stereo SAR, Rugged Terrain, Polar Format Algorithm, PFA, Spotlight SAR, Spotlight-mode data. 
    @conference{yockyJakowatzStereoHeightExatraction,
author = {David A. Yocky and Charles V. Jakowatz, Jr.},
editor = {Andrew G. Tescher},
collaboration = {},
title = {Automated wide-angle {SAR} stereo height extraction in rugged terrain using shift-scaling correlation},
publisher = {SPIE},
year = {2003},
journal = {Applications of Digital Image Processing XXVI},
volume = {5203},
number = {1},
pages = {10-20},
location = {San Diego, CA, USA},
url = {http://link.aip.org/link/?PSI/5203/10/1},
doi = {10.1117/12.502706},
keywords = {SAR Processing, Stereo SAR, Rugged Terrain, Polar Format Algorithm, PFA, Spotlight SAR, Spotlight-mode data},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/yockyJakowatzStereoHeightExatraction.pdf},
owner = {ofrey},

}


Internal reports

  1. Michiel Otten and Henno Boomkamp. Estimation of the Absolute Orbit Accuracy of Envisat. Technical report, European Space Operations Centre (ESOC), Robert-Bosch Strasse 5, D-64283 Darmstadt, 2003.
    Keywords: ENVISAT, DORIS, Precise Orbit, Orbit, Orbit Accuracy, Accuracy, ASAR.
    Abstract: This paper presents the results of the orbit comparison campaign conducted at the European Space Operations Centre (ESOC) in May 2003. The goal of the comparison is to better quantify the absolute orbit accuracy of ENVISAT. For this comparison cycle 12 of ENVISAT was selected which corresponds to a period of 35 days starting at 10.12.2002 and ending at 13.01.2003. Two days, 18 and 19 December, were excluded within this period from the comparison. These days were selected because of the large inclination manoeuvre on 18 December and the resulting loss of DORIS and SLR tracking data for nearly a day. Six different centers contributed their POD solution to the comparison. The CNES POD solution used in this comparison is the same solution as the one that is found on the ENVISAT altimeter GDR. The JPL-DORIS solution only uses the DORIS tracking dataset and is based on the EGM- 96 gravity field where all the other centers use DORIS and SLR data and the GRIM5-C1 field. Three complementary analysis methods where applied to all contributions, namely pair-wise orbit comparison, SLR tracking data analysis and altimeter crossover analysis. 

    @TECHREPORT{ottenBoomkamp03:DorisAbsAccuracy,
author = {Michiel Otten and Henno Boomkamp},
title = {{Estimation of the Absolute Orbit Accuracy of Envisat}},
institution = {European Space Operations Centre (ESOC)},
year = {2003},
address = {Robert-Bosch Strasse 5, D-64283 Darmstadt},
abstract = {This paper presents the results of the orbit comparison campaign conducted at the European Space Operations Centre (ESOC) in May 2003. The goal of the comparison is to better quantify the absolute orbit accuracy of ENVISAT. For this comparison cycle 12 of ENVISAT was selected which corresponds to a period of 35 days starting at 10.12.2002 and ending at 13.01.2003. Two days, 18 and 19 December, were excluded within this period from the comparison. These days were selected because of the large inclination manoeuvre on 18 December and the resulting loss of DORIS and SLR tracking data for nearly a day. Six different centers contributed their POD solution to the comparison. The CNES POD solution used in this comparison is the same solution as the one that is found on the ENVISAT altimeter GDR. The JPL-DORIS solution only uses the DORIS tracking dataset and is based on the EGM- 96 gravity field where all the other centers use DORIS and SLR data and the GRIM5-C1 field. Three complementary analysis methods where applied to all contributions, namely pair-wise orbit comparison, SLR tracking data analysis and altimeter crossover analysis.},
keywords = {ENVISAT, DORIS, Precise Orbit, Orbit, Orbit Accuracy, Accuracy, ASAR},
owner = {ofrey},
pdf = {http://www.geo.uzh.ch/~ofrey/protected/PAPERS/ottenBoomkamp03.pdf},
url = {http://nng.esoc.esa.de/envisat/results/campaign.pdf} 
}



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Please note that access to full text PDF versions of papers is restricted to the Remote Sensing Laboratories of the University of Zürich.
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: Wed Sep 8 19:32:46 2010
Author: Othmar Frey , Remote Sensing Laboratories (RSL), University of Zurich, Switzerland .

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