ADAPTIVE SPECKLE FILTERS AND SCENE HETEROGENEITY

The presence of speckle in radar images makes the radiometric and textural aspects less efficient for class discrimination. Many adaptive filters have been developed for speckle reduction. In this paper, the most well-known filters are analyzed. It is shown that they are based on a test related to the local coefficient of variation of the observed image, which describes the scene heterogeneity. Some practical criteria are then introduced to modify the filters in order to make them more efficient. The filters are tested on a simulated SAR image and a SAR-580 image. As was expected, the new filters perform better, i.e., they average the homogeneous areas better and preserve texture information, edges, linear features, and point target responses better at the same time. Moreover, they can be adapted to features other than the coefficient of variation to reduce the speckle and at the same time preserve the corresponding information. © 1990, IEEE.