An improved four-component decomposition with distributed double-bounce scattering model

This paper proposes an improved four-component scattering decomposition scheme with modified double-bounce scattering model for the analysis of polarimetric synthetic aperture radar (POLSAR) data. In the Yamaguchi decomposition, it occurs occasionally for some pixels with negative surface scattering power Ps and/or negative diplane scattering power Pd because the whole HV cross-polarized component is assigned to volume scattering due to vegetation; and it is also difficult to discriminate man-made buildings not orthogonal to the radar LOS from vegetation. In advance the conditions of the emergence of negative powers in the Yamaguchi decomposition are given out, and three corresponding processing methods adopted in many improved four-component target decompositions are reviewed in the paper. Then the expression of the coherency matrix of distributed dielectric dihedral corner reflectors is derived. The expression demonstrates that distributed dielectric dihedral corner reflectors also will generate HV cross-polarized component. The new target decomposition utilizes the new double bounce model of distributed dielectric dihedral corner reflectors instead of the original one adopted by the Freeman and Yamaguchi decompositions. In order to solve the new decomposition, we introduce normalize circular-pol correlation coefficients to characterize the percentage of HV scattering component generated by distributed dielectric dihedral corner reflectors. An airborne L band quad-pol data acquired by DLR ESAR sensor over Oberpfaffenhoffen in German are applied to the improved decomposition scheme. Experimental results demonstrate that the new decomposition method can reduce the pixels with negative powers and obtain correct scattering mechanisms of non-reflection structures not paralleled to the flight path.