OPTIMAL SPECKLE REDUCTION IN POLARIMETRIC SAR IMAGERY

Speckle is a major cause of degradation in synthetic aperture radar (SAR) imagery With the availability of fully polarimetric SAR data, it is possible to use the three complex elements (HH,HV,VV) of the polarimetric scattering matrix to reduce speckle. The optimal method for combining the elements of the scattering matrix to minimize image speckle is derived here, and the solution is shown to be a polarimetric whitening filter (PWF). A simulation of spatially correlated, K-distributed, fully polarimetric clutter is then used to compare the PWF with other, suboptimal speckle-reduction methods. Target detection performance of the PWF, span, and single-channel |HH|2 detectors is compared with the optimal polarimetric detector (OPD). Finally, a new, constant false-alarm rate (CFAR) detector (the adaptive PWF) is proposed as a simple alternative to the OPD for detecting targets in clutter. This algorithm estimates the polarization covariance of the clutter, uses this covariance to construct the minimum speckle image, and then tests for the presence of a target. An exact theoretical analysis of the adaptive PWF is presented; the algorithm is shown to have detection performance comparable with that of the OPD. © 1990 IEEE