A change detection measure based on a likelihood ratio and statistical properties of SAR intensity images

With its weather-and illumination-independent characteristics, synthetic aperture radar (SAR) has become an important tool for change detection. There are two critical steps in SAR image change detection: designing a change detector and choosing a decision rule. Given a measure from a change detector, the change detection results could be sensitive to the decision rule, such as the selection of a threshold. This letter presents a change detection measure based on a likelihood ratio and the statistical distribution of SAR intensity images. The likelihood ratio is defined as the ratio between the joint probability density functions (PDFs) of a pair of SAR images. Under the condition that both PDFs follow the gamma distribution, the histogram of this change detection measure deduced from the likelihood ratio has a single and steep peak that can be used to reliably and easily determine the change detection threshold. Analyses of SAR image pairs from different platforms show that the proposed change detection measure is simple and effective in detecting changes.