A multi-filtering approach to adaptive speckle reduction in textured SAR images

Speckle reduction in synthetic aperture radar (SAR) images is a key point to facilitate applicative tasks. A filter aimed at speckle reduction should energetically smooth homogeneous regions, while preserving point targets, edges, and linear features. A tradeoff, however, should be arranged on textured areas. Filtering capabilities depend on local image characteristics, and generally no filter outperforms the others in every situation. In this work, a set of adaptive filters is considered with attention to those oriented towards a multiresolution approach. Images are individually processed by each filter, and the output at each pixel position is obtained by choosing one out of the channels. The selection is based on thresholding local features accounting for both space-varying statistics and geometry. Results on true SAR images show that also an empirical choice of thresholds is noncritical: the novel scheme outperforms each filter individually, at least according to visual criteria.