Comparison of Compact Polarimetric Synthetic Aperture Radar Modes
TL;DR: Modifications of the original reconstruction algorithm proposed by Souyris are discussed, which show potential to better reconstruct fully polarimetric data.
Abstract: Compact polarimetry is a technique that allows construction of pseudo quad-pol information from dual-polarization synthetic aperture radar (SAR) systems. Compact polarimetry showed promise of being able to reduce the complexity, cost, mass, and data rate of a SAR system while attempting to maintain many capabilities of a fully polarimetric system. In this paper, we study different transmit/receive configurations to determine which polarimetric configurations allow for superior reconstruction of the fully polarimetric data. We discuss modifications of the original reconstruction algorithm proposed by Souyris , which show potential to better reconstruct fully polarimetric data.
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TL;DR: A synthetic aperture radar (SAR) with hybrid-polarity (CL-pol) architecture transmits circular polarization and receives two orthogonal, mutually coherent linear polarizations, which is one manifestation of compact polarimetry as mentioned in this paper.
Abstract: A synthetic aperture radar (SAR) with hybrid-polarity (CL-pol) architecture transmits circular polarization and receives two orthogonal, mutually coherent linear polarizations, which is one manifestation of compact polarimetry. The resulting radar is relatively simple to implement and has unique self-calibration features and low susceptibility to noise. It also enables maintenance of a larger swath coverage than fully polarimetric SAR systems. A research team composed of various departments of the Government of Canada evaluated this compact polarimetry mode configuration for application to soil moisture estimation, crop identification, ship detection, and sea-ice classification. This paper presents an overview of compact polarimetry, the approach developed for evaluation, and preliminary results for applications important to the Government of Canada. The implications of the results are also discussed with respect to future SAR missions such as the Canadian RADARSAT Constellation Mission, the American DESD...
253 citations
Cites background or result from "Comparison of Compact Polarimetric ..."
...Worldwide, more and more investigations (Dubois-Fernandez et al., 2008; Nord et al., 2009; Charbonneau et al., 2009; Ainsworth et al., 2009) are aimed at validating these ‘‘as good as’’ and ‘‘much better than’’ assertions as they relate to specific applications....
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...There are several studies that compare these two methods when applied to a known dataset (Nord et al., 2009; Ainsworth et al., 2009)....
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...Approximations are feasible (Souyris et al., 2005; Nord et al., 2009), but the errors associated with retrieval of linear polarizations from CL-pol are too high for quantitative estimation in applications such as soil moisture (Charbonneau, 2009)....
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TL;DR: A short review is presented on the recent trend and development of SAR and related techniques with selected topics, including the fields of applications, specifications of airborne and spaceborne SARs, and information contents in and interpretations of amplitude data, interferometric SAR (InSar) data, and polarimetric SAR (PolSAR) data.
Abstract: The present article is an introductory paper in this special issue on synthetic aperture radar (SAR). A short review is presented on the recent trend and development of SAR and related techniques with selected topics, including the fields of applications, specifications of airborne and spaceborne SARs, and information contents in and interpretations of amplitude data, interferometric SAR (InSAR) data, and polarimetric SAR (PolSAR) data. The review is by no means extensive, and as such only brief summaries of of each selected topics and key references are provided. For further details, the readers are recommended to read the literature given in the references theirin.
235 citations
TL;DR: The purpose of this paper is to review the current status of soil moisture determination from active microwave remote sensing systems and to highlight the key areas of research that will have to be addressed to achieve routine use of the proposed retrieval approaches.
Abstract: The importance of land surface-atmosphere interactions, principally the effects of soil moisture, on hydrological, meteorological, and ecological processes has gained widespread recognition over recent decades. Its high spatial and temporal variability however, makes soil moisture a difficult parameter to measure and monitor effectively using traditional methods. Microwave remote sensing technology has demonstrated the potential to map and monitor relative soil moisture changes over large areas at regular intervals in time and also the opportunity of measuring, through inverse modelling, absolute soil moisture values. This ability has been demonstrated under a variety of topographic and land cover conditions using both active and passive microwave instruments. The purpose of this paper is to review the current status of soil moisture determination from active microwave remote sensing systems and to highlight the key areas of research that will have to be addressed to achieve routine use of the proposed retrieval approaches.
190 citations
Cites methods from "Comparison of Compact Polarimetric ..."
...Fully polarimetric SAR (PolSAR) and also Compact Polarimetric SAR [167-170] measurements have been used to study the dependence of the polarimetric signature on land cover changes and on surface parameters such as soil moisture and surface roughness....
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...Fully polarimetric SAR (PolSAR) and also Compact Polarimetric SAR [167-170] measurements have been used to study...
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TL;DR: In this paper, a new technique derived from the classical Stokes parameters for analysis of polarimetric radar astronomical data is introduced, based on m (the degree of polarization) and chi (the Poincare ellipticity parameter).
Abstract: [1] We introduce a new technique derived from the classical Stokes parameters for analysis of polarimetric radar astronomical data. This decomposition is based on m (the degree of polarization) and chi (the Poincare ellipticity parameter). Analysis of the crater Byrgius A demonstrates how m-chi can more easily differentiate materials within ejecta deposits and their relative thicknesses. We use Goldschmidt crater to demonstrate how m-chi can differentiate coherent deposits of water ice. Goldschmidt crater floor is found to be consistent with single bounce Bragg scattering suggesting the absence of water ice and further corroborating adsorbed H to mineral grains or an H2O frost as plausible explanations for a H2O/OH detection by near-infrared instruments.
176 citations
TL;DR: This letter develops several new aspects of target decomposition theory for use with compact-mode polarimetric radar data, and shows that, under certain assumptions, compact data can be used to estimate the rotation invariant alpha angle of quadpol systems.
Abstract: In this letter, we develop several new aspects of target decomposition theory for use with compact-mode polarimetric radar data. We first make a general link between fully polarimetric systems and compact modes before developing two important types of decomposition, namely, entropy/alpha and model-based surface/dihedral/volume techniques. We show that, under certain assumptions, compact data can be used to estimate the rotation invariant alpha angle of quadpol systems, which can then be used for polarimetric classification and physical parameter estimation. We apply the new methods to the problem of historical forest fire scar detection, using data at L- and C-bands to demonstrate the preservation of signatures in transition from quad to compact modes.
174 citations
Additional excerpts
...THE NEW CANADIAN Radar Constellation Mission, which is a follow-up to Radarsat-2, and Advanced Land Observation Satellite (ALOS) 2, which is the Japanese Lband follow-up to Phased-Array-type L-band Synthetic Aperture Radar (PALSAR), both propose a new polarimetric mode called compact [1]–[5], which comprises a hybrid mode, first proposed in [1] and subsequently developed in [3], single transmit polarization (usually circular), and simultaneous coherent orthogonal linear receive....
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References
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TL;DR: The authors outline a new scheme for parameterizing polarimetric scattering problems that relies on an eigenvalue analysis of the coherency matrix and employs a three-level Bernoulli statistical model to generate estimates of the average target scattering matrix parameters from the data.
Abstract: The authors outline a new scheme for parameterizing polarimetric scattering problems, which has application in the quantitative analysis of polarimetric SAR data. The method relies on an eigenvalue analysis of the coherency matrix and employs a three-level Bernoulli statistical model to generate estimates of the average target scattering matrix parameters from the data. The scattering entropy is a key parameter is determining the randomness in this model and is seen as a fundamental parameter in assessing the importance of polarimetry in remote sensing problems. The authors show application of the method to some important classical random media scattering problems and apply it to POLSAR data from the NASA/JPL AIRSAR data base.
2,262 citations
"Comparison of Compact Polarimetric ..." refers background or methods in this paper
...The three outlined areas demark (from left to right) the urban (double-bounce scattering), grass (surface scattering), and forest (volume scattering) regions over which the entropy and α-angles [8] are examined in Section IV....
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...Cloude–Pottier entropy and α-angle parameters [8] were calculated for the original full quad-pol data set and for the three reconstructed data sets....
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...Cloude–Pottier entropy and α-angle parameters [8] of an Ingara X-band SAR scene quite well....
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TL;DR: An approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric SAR observations, which is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem.
Abstract: An approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric SAR observations. The mechanisms are canopy scatter from a cloud of randomly oriented dipoles, evenor double-bounce scatter from a pair of orthogonal surfaces with different dielectric constants and Bragg scatter from a moderately rough surface. This composite scattering model is used to describe the polarimetric backscatter from naturally occurring scatterers. The model is shown to describe the behavior of polarimetric backscatter from tropical rain forests quite well by applying it to data from NASA/Jet Propulsion Laboratory's (JPLs) airborne polarimetric synthetic aperture radar (AIRSAR) system. The model fit allows clear discrimination between flooded and nonflooded forest and between forested and deforested areas, for example. The model is also shown to be usable as a predictive tool to estimate the effects of forest inundation and disturbance on the fully polarimetric radar signature. An advantage of this model fit approach is that the scattering contributions from the three basic scattering mechanisms can be estimated for clusters of pixels in polarimetric SAR images. Furthermore, it is shown that the contributions of the three scattering mechanisms to the HH, HV, and VV backscatter can be calculated from the model fit. Finally, this model fit approach is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem.
2,079 citations
TL;DR: A maximum likelihood classifier to segment polarimetric SAR data according to terrain types has been developed based on the Wishart distribution, which can be applied to multifrequency multi-look polarimetry SAR data, as well as 10 SAR data containing only intensity information.
Abstract: Multi-look polarimetric SAR (synthetic aperture radar) data can be represented either in Mueller matrix form or in complex covariance matrix form. The latter has a complex Wishart distribution. A maximum likelihood classifier to segment polarimetric SAR data according to terrain types has been developed based on the Wishart distribution. This algorithm can also be applied to multifrequency multi-look polarimetric SAR data, as well as 10 SAR data containing only intensity information. A procedure is then developed for unsupervised classification. The classification error is assessed by using Monte Carlo simulation of multilook polarimetric SAR data, owing to the lack of ground truth for each pixel. Comparisons of classification errors using the training sets and single-look data are also made. Applications of this algorithm are demonstrated with NASA/JPL P-, L- and C-band polarimetric SAR data.
717 citations
"Comparison of Compact Polarimetric ..." refers methods in this paper
...Here, we simply quote results of a simulation of Wishart statistically distributed polarimetric returns based on the covariance matrix given by (A1) and the simulation technique described in [12]....
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01 Jul 2006
TL;DR: Data from a CL-pol SAR yield to decomposition strategies such as the m-delta method introduced in this paper, which is the architecture of choice for two lunar radars scheduled for launch in 2008.
Abstract: A synthetic aperture radar (SAR) often is constrained to transmit only one polarization. Within this constraint, two aggressive measurement objectives are 1) full characterization and exploitation of the backscattered field, and 2) invariance to geometrical orientations of features in the scene. Full characterization implies coherent dual-polarization to support the four Stokes parameters. These are rotationally invariant with respect backscatterer orientation if and only if the transmission is circularly polarized. Given that the data products are the Stokes parameters, the receivers can use any orthogonal polarization basis. A SAR in hybrid-polarity architecture (CL-pol) transmits circular polarization and receives two orthogonal mutually coherent linear polarizations, which is one manifestation of compact polarimetry. The resulting radar is relatively simple to implement, and has unique self-calibration features and low susceptibility to noise and cross-channel errors. It is the architecture of choice for two lunar radars scheduled for launch in 2008. Data from a CL-pol SAR yield to decomposition strategies such as the m-delta method introduced in this paper.
490 citations
TL;DR: The polarization uniqueness in transmission of this mixed basis mode, hereafter referred to as the /spl pi//4 mode, maintains the standard lower pulse repetition frequency operation and hence maximizes the coverage of the sensor.
Abstract: We assess the performance of synthetic aperture radar (SAR) compact polarimetry architectures based on mixed basis measurements, where the transmitter polarization is either circular or orientated at 45/spl deg/(/spl pi//4), and the receivers are at horizontal and vertical polarizations with respect to the radar line of sight. An original algorithm is proposed to reconstruct the full polarimetric (FP) information from this architecture. The performance assessment is twofold: it first concerns the level of information preserved in comparison with FP, both for point target analysis and crop fields classification, using L-band SIRC/XSAR images acquired over Landes forest and Jet Propulsion Laboratory AIRSAR images acquired over Flevoland. Then, it addresses the space implementation complexity, in terms of processed swath, downloading features, power budget, calibration, and ionospheric effects. The polarization uniqueness in transmission of this mixed basis mode, hereafter referred to as the /spl pi//4 mode, maintains the standard lower pulse repetition frequency operation and hence maximizes the coverage of the sensor. Because of the mismatch between transmitter and receiver basis, the power budget is deteriorated by a factor of 3 dB, but it can partly be compensated.
322 citations
"Comparison of Compact Polarimetric ..." refers background in this paper
...2 for descriptions of the plots and to compare with the original compact polarimetric algorithm [5]....
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...[5] proposed a relationship between the magnitude of the linear coherence |ρ| and the cross-pol ratio (〈|SHV|(2)〉/(〈|SHH|(2)〉 + 〈|SVV|(2)〉)), i....
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...These constants do not have an impact on the polarimetric performance of compact polarimetry modes but will have an effect on the power budget of SAR hardware [5]....
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...Several recent papers [5], [6] have demonstrated that dualpol SAR systems can reproduce aspects of fully polarimetric data based on a few simple assumptions....
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...This simplification applies reasonably well in general analysis of natural scatterers at various frequencies and for different spatial averaging windows [5], [6]....
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