A PS-based approach for the calilbration of spaceborne polarimetric SAR systems

The paper debates an external calibration approach based on the stable natural targets, namely Permanent Scatterers (PS), that can be spotted in the illuminated frame. The method, hereby called PolPSCal, allows for relative calibration of the full 4 by 3 polarimetric distortion matrices (PDMs) affecting the stack images. The algorithm is neither constrained to a particular PDM model (thus its implementation is practically feasible for any SAR sensor) nor to any external information. These latter are eventually demanded afterwards in order to normalize the returned PDM stack to an absolute reference. The PolPSCal mathematical framework is reported, and a performance analysis with concern to the PS detection and the PDM estimates accuracy is carried out on both synthetic data and a 29 images RADARSAT-2 dataset.