Compact Polarimetric SAR Interferometry Target Decomposition With the Freeman–Durden Method

In this paper, we apply the Freeman–Durden decomposition method to the compact polarimetric synthetic aperture radar (SAR) interferometry (C-PolInSAR) data. The complex cross-correlation matrix of the single-baseline C-PolInSAR is decomposed into three $2\times 2$ covariance matrices, which correspond to the surface, the dihedral and the volume scattering, respectively. Under reasonable assumptions, each model of the three scattering mechanisms are derived and formulated in term of the $\pi /4$ C-PolInSAR mode and the circular polarization transmitting and linear polarization reception (CTLR) C-PolInSAR mode. Prior to the target decomposition, detailed steps to retrieve the volume scattering amplitude are given, which are remarkably different for the $\pi /4$ mode and the CTLR mode. In addition, the topographic phase is also retrieved based on the random volume over ground (RVoG) model with the C-PolInSAR data. Finally, a numerical method is applied to solve the system of nonlinear equations in the target decomposition procedure, and the amplitude contributions, as well as the vertical phase center heights are retrieved for each of the three scattering mechanisms with the C-PolInSAR data. The proposed target decomposition method has been verified both with a simulated forest data, and with the L -band BioSAR2008 airborne data acquired by the DLR E-SAR system of a forest site in the north of Vindeln municipality, Sweden, wherein detailed performance results for the proposed method are presented as compared to the more usual quad polarimetric SAR interferometry target decomposition.