Polarimetric Incoherent Target Decomposition by Means of Independent Component Analysis

International audienceThis paper presents an alternative approach for polarimetric incoherent target decomposition dedicated to the analysis of very-high resolution POLSAR images. Given the non-Gaussian nature of the heterogeneous POLSAR clutter due to the increase of spatial resolution, the conventional methods based on the eigenvector target decomposition can ensure uncorrelation of the derived backscattering components at most. By introducing the Independent Component Analysis (ICA) in lieu of the eigenvector decomposition, our method is rather deriving statistically independent components. The adopted algorithm - FastICA, uses the non-Gaussianity of the components as the criterion for their independence. Considering the eigenvector decomposition as being analogues to the Principal Component Analysis (PCA), we propose the generalization of the ICTD methods to the level of the Blind Source Separation (BSS) techniques (comprising both PCA and ICA). The proposed method preserves the invariance properties of the conventional ones, appearing to be robust both with respect to the rotation around the line of sight and to the change of the polarization basis. The efficiency of the method is demonstrated comparatively, using POLSAR Ramses X-band and ALOS L-band data sets. The main differences with respect to the conventional methods are mostly found in the behaviour of the second most dominant component, which is not necessarily orthogonal to the first one. The potential of retrieving non-orthogonal mechanisms is moreover demonstrated using synthetic data. On expense of a negligible entropy increase, the proposed method is capable of retrieving the edge diffraction of an elementary trihedral by recognizing dipole as the second component

Analysis of supplementary information emerging from the ICA based ICTD

International audienceThis paper presents an elaboration of the ICA based ICTD, proposed in [1]. The method is applied on three different datasets and three distinctive aspects of its performances are considered. Firstly, we challenge the initial choice of the ICA algorithm, by testing the suitability of two representative tensorial (fourth-order) and one second-order algorithm. Further, we demonstrate the invariance of the proposed decomposition with respect to both the rotation around the line of sight and the change of polarisation basis. Finally, we analyse the potential of supplementary information contained in the second most dominant component

Independent component analysis within polarimetric incoherent target decomposition

International audienceThis paper represents a part of our efforts to generalize polarimetric incoherent target decomposition to the level of BSS techniques by introducing the ICA method instead of the conventional eigenvector decomposition. We compare, in the frame of polarimetric incoherent target decomposition, several criteria for the estimation of complex independent components. This is done by parametrising the obtained dominant and mutually independent target vectors using the TSVM and representing them on the corresponding Poincare sphere. We demonstrate notably good performances of the proposed method applied on the RAMSES POLSAR X-band image, by precisely identifying the class of trihedral reflectors present in the scene. Logarithm and square root nonlinearities - two of the three proposed criteria for complex IC derivation prove to be very efficient. The best discrimination between the a priori defined classes appears to be achieved with the principal kurtosis criterion. Finally, the algorithm using the former two functions leads to very interesting entropy estimation

Evaluation of Multilook Effect in ICA Based ICTD for PolSAR Data Analysis

International audiencePolarimetric incoherent target decomposition aims in accessing physical parameters of illuminated scatters through the analysis of target coherence or covariance matrix. In this framework, Independent Component Analysis (ICA) was recently proposed as an alternative method to eigenvector decomposition to better interpret non-Gaussian heterogeneous clutter (inherent to high resolution SAR systems). In this paper a Monte Carlo approach is performed in order to investigate the bias in estimating Touzi's Target Scattering Vector Model parameters when ICA is employed. Simulated data and data from the P-band airborne dataset acquired by the Office National d'tudes et de Recherches Arospatiales (ON-ERA) over the French Guiana in 2009 in the frame of the European Space Agency campaign TropiSAR are taken into consideration

Blind Source Separation in Polarimetric SAR Interferometry

International audiencePolarimetric incoherent target decomposition aims in access-ing physical parameters of illuminated scatters through the analysis of target coherence or covariance matrix. In this framework, Independent Component Analysis (ICA) was recently proposed as an alternative method to Eigenvector decomposition to better interpret non-Gaussian heterogeneous clutter (inherent to high resolution SAR systems). Until now, the two main drawbacks reported of the aforementioned method are the greater number of samples required for an unbiased estimation, when compared to classical Eigenvector decomposition and the inability to be employed in scenarios under Gaussian clutter assumption. First, a Monte Carlo approach is performed in order to investigate the bias in estimating the Touzi Target Scattering Vector Model (TSVM) parameters when ICA is employed. A RAMSES X-band image acquired over Brétigny, France is taken into consideration to investigate the bias estimation under different scenarios. Finally, some results in terms of POLinSAR coherence optimization [1] in the context of ICA are proposed

Evaluation of the New Information in the H/α Feature Space Provided by ICA in PolSAR Data Analysis

International audienceThe Cloude and Pottier H/α feature space is one of the most employed methods for unsupervised polarimetric synthetic aperture radar (PolSAR) data classification based on incoherent target decomposition (ICTD). The method can be split in two stages: the retrieval of the canonical scattering mechanisms present in an image cell and their parameterization. The association of the coherence matrix eigenvectors to the most dominant scattering mechanisms in the analyzed pixel introduces unfeasible regions in the H/α plane. This constraint can compromise the performance of detection, classification, and geophysical parameter inversion algorithms that are based on the investigation of this feature space. The independent component analysis (ICA), recently proposed as an alternative to eigenvector decomposition, provides promising new information to better interpret non-Gaussian heterogeneous clutter (inherent to highresolution SAR systems) in the frame of polarimetric ICTDs. Not constrained to any orthogonality between the estimated scattering mechanisms that compose the clutter under analysis, ICA does not introduce any unfeasible region in the H/α plane, increasing the range of possible natural phenomena depicted in the aforementioned feature space. This paper addresses the potential of the new information provided by the ICA as an ICTD method with respect to Cloude and Pottier H/α feature space. A PolSAR data set acquired in October 2006 by the E-SAR system over the upper part of the Tacul glacier from the Chamonix Mont Blanc test site, France, and a RAMSES X-band image acquired over Brétigny, France, are taken into consideration to investigate the characteristics of pixels that may fall outside the feasible regions in the H/α plane that arise when the eigenvector approach is employed