Speckle reducing for Sentinel-1 SAR data

Data provided by synthetic aperture radar (SAR) of Sentinel satellite can be useful for many applications. However, as for any SAR image, speckle noise is present in acquired images. Speckle properties are important for different operations of SAR image processing as filtering, edge detection, segmentation, classification. Thus, we first carry out preliminary analysis of speckle statistics and show that speckle PDF is quite close to Gaussian whilst noise is of practically multiplicative nature. Second, spatial correlation properties of speckle are analyzed. The study is performed in local DCT domain. This is done since then the obtained 2D spectrum is employed in image despeckling based on DCT. Peculiarities of several possible approaches to despeckling are discussed. Several examples for one component and dual polarization data are presented.