Terrain radiometric calibration of airborne UAVSAR for forested area

In the field of biomass estimation,terrain radiometric calibration of airborne polarimetric SAR data for forested areas is an urgent problem.Illuminated area correction ofσ-naught could not completely remove terrain features.Inspired by Small and Shimada,this paper tested gamma-naught on one mountainous forested area using airborne Uninhabited Aerial Vehicle Synthetic Aperture Radar data and found it could remove most terrain features.However,a systematic increasing trend from far range to near range is found in airborne SAR cases.This paper made an attempt to use the relationship between distance to SAR sensor andγ-naught to calibrateγ-naught.Two quantitative evaluation methods are proposed.Experimental results demonstrate that variation ofγ-naught can be constrained to a limited extent from near range to far range.Since this method is based on ground range images,it avoids complicated orthorectification.