Investigation on the Effects of Polarization Orientation Angle Shift in the UAVSAR Polarimetric Decomposition

Abstract

The polarization orientation angle (POA) shift results in higher cross-polarization intensity in the HV and VH channels making the reflection asymmetrical. The L-band quad-pol dataset acquired over the Fujiyama mountain, Japan by the Uninhabited Aerial Vehicle Synthetic Aperture Radar of JPL/NASA was used in this study to analyse the effect of POA shift in the polarimetric decomposition techniques. The dataset was first compensated for the POA shift using the circular polarization algorithm, and a mean polarization orientation angle shift of − 4.23° was estimated. The Yamaguchi 3-component model-based decomposition and the H/A/Alpha eigenvector-based decomposition techniques were performed on the dataset before and after POA compensation. It was found that there was an overestimation of volume scattering component and underestimation of double-bounce scattering component before POA compensation in the Yamaguchi 3-component decomposition technique. After the POA compensation, there was a significant reduction in the volume scattering component observed at the non-vegetated areas and increase in double-bounce scattering in the same areas. There was no considerable change observed in the surface scattering component because of its roll invariant nature. Since the H/A/Alpha decomposition parameters were also independent of the orientation angle change because of their roll invariance property, there was no change observed in those parameters after POA compensation.