OBSERVATION OF UNZEN/FUGEN VOLCANO BY JERS-1/SAR

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Synthetic Aperture Radar (SAR) images by JERS-1 are enhanced by reducing speckle noise. The Gamma MAP filter by Lopes et al.has been applied to ERS-1/SAR or C-SAR images, and they successfully obtained the speckle reduced images. The speckle is reduced as a function of the coefficient of variation within a local window in the Gamma MAP filter, in which the threshold values are used to classify pixels. The theoretical estimate of the thresholds by the Gamma MAP filtering algorithm for JERS-1/SAR images is quite different from the estimate by the present analysis of the distribution of the coefficient of variation for 1-look, 2-look, and 3-look processes. These thresholds for JERS-1/SAR images are determined based on the distribution of the observed local coefficient of variaiton within a window. SAR images with good quality are obtained by the present method of estimating the thresholds.