Analysis of speckle filtering in polarimetric SAR imagery

The principle of speckle reduction in polarimetry is reconsidered. It is shown that polarimetric data can be speckle reduced if and only if all the elements of the Mueller matrix are filtered, which is equivalent to filtering the scattering vector covariance matrix. Assuming that speckle is multiplicative and stationary, the method proposed by Goze et al. (1993) is extended to filter the covariance matrix of reciprocal and non-reciprocal targets on one-look and multi-look images. The usual methods of estimation of the first and second order speckle statistics are discussed, and a solution is proposed for one-look and multi-look images