Multiresolution analysis of SAS images

Detection and classification of underwater mines with Synthetic Aperture Sonar (SAS) images is a challenge that can be performed in studying either the echoes or the shadows of mines. However, SAS images present a strong speckle level due to the construction of the image itself. To reduce this speckle level, filtering methods are generally used but all of them strongly deteriorate either the shadow or the echo of the mine. In this article, we propose a new speckle reduction method which allows enhancing jointly mines echoes and shadows. This new process is based on the marriage between a multiresolution transformation and a filtering method. Results obtained on real SAS data are presented and compared with those obtained using classical processing.