On the estimation of polarization orientation angles induced from azimuth slopes using polarimetric SAR data

In recent studies, Schuler et al. (1996) applied the polarimetric SAR (POLSAR) derived orientation angles to measure topography, and Lee et al. (1999) used the orientation angles for polarimetric SAR data compensation, to ensure accurate estimation of geophysical parameters, such as, biomass, soil moisture, and surface roughness, in rugged terrain area. Consequently, it is important to accurately estimate orientation angles that were induced by the azimuth slope variations. However, in these studies, inconsistency in the estimation of orientation angles was encountered in several areas, introducing noisy and erroneous results. Two methods have been proven to be effective in the orientation angle estimation. The peak-seeking method in polarization signatures was a credible one. The other method is based on the circular polarizations in which the phase difference between right-right circular and left-left circular polarization is used to estimate the orientation angles. The present authors explore a theoretical model based on Bragg scattering, to verify the circular polarization method, and to discover problems associated with orientation estimation and data compensation. The advantage of applying polarimetric SAR speckle filter is also investigated.