Speckle Reduction of Synthetic Aperture Sonar Images
نویسندگان
چکیده
Multi-look processing is a well known technique for reducing speckle in coherent imagery. This paper investigates the use of multi-look processing in range (frequency-compounding) on SAS images. The coherence between sub-images produced by frequency compounding is determined and a coherence model proposed. This is used to calculate the level of speckle reduction for a given number of looks and spectral displacement. This shows that the optimal level of speckle reduction for a given loss in resolution is achieved when the spectral windows are displaced by approximately one third their bandwidth. The level of speckle reduction obtained using frequency compounding was measured for field SAS images and compared to the model. The number of looks used can be varied to trade-off the desired levels of speckle reduction and resolution loss. The number of looks that maximises the detectability ratio of speckle reduction to resolution loss is then experimentally measured.
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