Subaperture analysis of polarimetric SAR imagery

In this paper we investigate the nonstationary behavior of individual polarimetric parameters, e.g. entropy, anisotropy, alpha angle, orientation angle, helicity, etc. We distinguish between parameters that depend solely on the eigenvalues of the standard Cloude-Pottier polarimetric decomposition (span, entropy and anisotropy) and the others that depend on the scattering mechanisms, i.e. the Cloude-Pottier eigenvectors. After producing a series of azimuth subaperture polarimetric images, we apply the polarimetric decomposition to each subaperture frame and identify subaperture frames that show nonstationary scattering. Comparison of several specific targets, both discrete and distributed, will highlight aspects of polarimetric variability with respect to the SAR view angle. We illustrate our results using EMISAR L-band polarimetric SAR data.