Speckle noise removal in SAR image based on SOT structure in wavelet domain

The Spatial-orientated tree (SOT) structure plays a very important role in wavelet-based image compression. Both the Embedded Zero-tree Wavelet (EZW) and the Set Partitioning in Hierarchical Trees (SPIHT) coding schemes utilize the parent-children relationship in SOT for image compression. The SOT is a very efficient data structure to be used for investigation of spatial correlations among wavelet coefficients at different resolutions. However, to the best knowledge of the authors, the SOT has not been widely used in noise suppression or image enhancement. This paper addresses this application and presents a novel denoising algorithm that utilizes the SOT to normalize the wavelet coefficients at different resolutions and remove the signal-dependence of the speckles before applying the thresholding scheme