Topographic relief compensation on spaceborne polarimetric SAR for forest applications

In order to use the advanced capabilities of polarimetric SAR data for forest applications, analysis methods must address topographic relief effects in mountainous regions. ALOS PALSAR L-band and Radarsat-2 C-band polarimetric SAR data over study sites in Hinton, Alberta, and the Greater Victoria Watershed District, BC, were collected and used to investigate the effectiveness of polarization orientation shifts correction, decomposition filtering techniques and local incident angle compensation. We found that the polarization orientation shifts estimated from PALSAR winter data corresponded to the topographic relief. The shifts from the PALSAR summer data were noisy. The polarization orientation shifts were not seen in the Radarsat-2 data. Various polarimetric parameterizations were useful for identifying terrain features and land cover types. The Cloude entropy, dominant scattering alpha and eigenvalues (lambda₂+lambda₃) were used to create HSV coding images for better differentiation of forest, vegetation and water surfaces with minimized topographic effects. The local incident angle compensation on single polarization backscatters was applied to Radarsat-2 data. Due to the high biomass volume in the study area and the higher radar frequency, the correlations between the polarization backscatter and the ground measured volumes at the plot level were poor.