Analysis of Compact Polarimetric Sar Imaging Modes

Recent interest in dual-pol SAR systems has lead to a novel approach to dual-pol SAR, the so-called compact polarimetric imaging mode. The original idea, presented by Souyris et al. [1], employed a SAR system transmitting a linearly polarized wave rotated by 45° with respect to the orientation of the vertical (V) and horizontal (H) receive antennas. One then constructed pseudo quad-pol data from the dual-pol data assuming reflection symmetry and a model relationship between the |HV| return and the HH-VV correlation coefficient. Recently Stacy and Preiss [2], and Nord et al. [3], presented extensions of the original dual-pol compact polarimetry ideas and, independently, Raney [4] has analyzed the Stokes parameters for dual-pol SAR systems. Here we briefly present the extensions of the original compact polarimetry ideas following the development in [3]. We then discuss the dual-pol signature plot and show that it provides a simple, visual means to assess the polarimetric content for any dual-pol SAR system that transmits a polarized wave of arbitrary ellipticity / orientation, and coherently receives any two orthogonal polarizations. Lastly, we consider the default dual-pol mode of ALOS PALSAR: H-transmit with coherent (V, H) receive. We provide an interpretation of the α-entropy plot for this (HH, HV) dual-pol data.