A WHITENING METHOD FOR THE DESPECKLING OF SAR IMAGES AFFECTED BY CORRELATED SPECKLE NOISE

In the last decade, several methods have been developed for the despeckling of Synthetically Aperture Radar (SAR) images. A considerable number of them have been derived on the assumption of the fully-developed speckle model in which the multiplicative speckle noise is supposed to be a white process. Unfortunately, the transfer function of SAR acquisition systems can introduce a statistical correlation which decreases the despeckling efficiency of such filters. In this work, a method for whitening a complex image acquired by a SAR system is proposed. By using the statistical properties of the acquired image the estimation of the SAR system frequency response is performed by means of some realistic assumptions; then a decorrelation process is applied on the acquired image, taking into account the presence of point targets. Finally, the image is despeckled. The experimental results show that the despeckling filters achieve better performance when they are preceded by the proposed whitening method; moreover, the radiometric characteristics of the image are preserved.