Polarimetric Calibration of L-Band UAVSAR Data

Abstract

The polarimetric distortion in the PolSAR datasets causes the polarimetric decomposition and classification techniques to produce wrong outputs, which result in misinterpreting the scattering phenomenon and the ground targets. The most important polarimetric distortions in airborne PolSAR datasets are the channel imbalance and crosstalk. The minimization of these polarimetric distortions using polarimetric calibration techniques is very important to carry out the quantitative analysis using PolSAR data and time-series analysis and to compare the results between different sensors. The objective of this study was to implement the external polarimetric calibration of the L-band UAVSAR system using trihedral corner reflectors. The polarimetric distortion matrix (PDM) was formulated after considering the crosstalk and channel imbalance polarimetric distortions to derive the scattering matrix free from all kinds of polarimetric distortions from the observed scattering matrix. The channel imbalance between different polarization channels was estimated with the help of trihedral corner reflectors and homogeneously distributed targets. The crosstalk parameters were estimated by assuming the scattering reciprocity constraint, which is valid in the case of monostatic radars. The scattering matrix free from polarimetric distortions was derived from the PDM after estimating the polarimetric distortions. The polarimetric signatures and the coherency matrix behaviour of the trihedral corner reflectors were used to analyse the ground target characterization improvement after polarimetric calibration.