Segmentation of SAR images

This paper presents a new algorithm for segmentation of SAR images based on threshold estimation using the histogram. The speckle distribution in (lie SAR image is modeled by a Gamma function. Thus, the SAR image histogram exhibits a combination of Gamma distributions. The maximum likelihood technique is therefore used to estimate the histogram parameters. This technique requires knowledge of the number of modes of the histogram, the number of looks of the SAR image, and the initial parameters of the histogram. The second derivative of the histogram is used to estimate the number of modes. We use two methods to estimate the number of looks. Initial parameters are estimated at the maximum of the Gamma function. Thresholds are selected at the valleys of a multi-modal histogram by minimizing the discrimination error between the classes of pixels in the image. The algorithm is applied to several RADARSAT SAR images with different number of looks, The results obtained are promising. (C) 2001 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.