Impact of Orthorectification on Simulated Compact Polarimetric RCM Data With Accurate Lidar DSM

Orthorectification using digital terrain models is a key issue for polarimetric complex synthetic aperture radar (SAR) data because resampling the complex data can corrupt the polarimetric phase, mainly in terrain with relief. Orthorectification will be also a sensitive issue with the compact polarimetric data of the future Canadian Radar Constellation Mission (RCM) sensor to be launched in 2018. Two orthorectification methods for the complex SAR data are thus proposed and compared: performing polarimetric processing in the image space before the geometric processing or in the ground space after the geometric processing. RCM compact polarimetric data using the requirements of the very high resolution (VHR) mode were simulated at the Canada Centre for Mapping and Earth Observation from fine-quad Radarsat-2 data acquired with different look angles over a hilly relief study site. Quantitative evaluations between the two methods, using a basis-invariant parameter (the entropy), were thus performed to evaluate the impact of orthorectification on the simulated VHR RCM data. To avoid the propagation of elevation errors into the final error budget, an accurate lidar digital surface model was used in the orthorectification. The results demonstrated that the oversampling and the noise floor that is used to generate the simulated VHR RCM data are the main factors, which corrupted the simulated VHR RCM data during its orthorectification with the ground-space method.