A mean based algorithm for the multi-temporal SAR image filtering

Any despeckling method for SAR images is a trade-off between speckle reduction level and preservation of image's resolution. The Time-Space Filter (TSF) proposed in III, despeckles the multi-temporal SAR images while preserving the radar reflectivity, the textures and the edges' contrast. The price paid for this features' integrity is a non-uniform despeckling: the speckle is reduced only in the homogenous areas, whereas the edges' vicinities and the textured areas remain noisy. In this paper, we propose a new version of the Time-Space Filter, the Mean based Time-Space Filter (M-TSF), which reduces everywhere the speckle, disregarding image's content. The residual noise in the images filtered by M-TSF remains multiplicative and stationary. This latter property makes M-TSF appropriate for pre-treatment in automatic edge detection. A comparison between M-TSF and Lee's filter for multipolarization SAR images [2] leads to an interesting conclusion: M-TSF is a frequential version of the Lee's filter.