Oil slick detection by SAR imagery: algorithms comparison

C-band SAR is well adapted to detect ocean pollution because backscatter is reduced by oil slicks. They appear as dark patches on the image as the increase of viscosity due to the presence of oil damps gravity-capillarity waves. In order to detect these dark patches, we use algorithms based on filters, gradients, and morphological mathematics, and a new approach based on ocean surface characterization. We have tested these methods on ERS and ENVISAT images acquired during Prestige tanker wreckage and the results are compared with aircraft surveys. We conclude that slicks with high contrast and simple shape are easily detected using basic algorithms, but most of the time, other methods are needed. The ocean characterization method is a way to follow for improving oil slick detection and providing, decision aids for classification step.