Polarimetric parameters for oil slicks detection using SAR data remote sensing — An evaluation

Oil slicks detection using remote sensing is of great interest for exploration, environment monitoring and crisis management. In an operational context, oil slicks are usually detected using airborne and/or spaceborne synthetic aperture radar (SAR). Many studies published in the literature have suggested to use polarimetric SAR (POLSAR) parameters to improve the detection capability of slicks; but no comprehensive comparison of those parameters have been proposed. Moreover, the oil layer present on the top of the sea surface will damp the so-called "capillarity wave" which are at the origin of the sea surface roughness; as a consequence, oil slick will appear as dark area on the SAR image (low backscattered signal). For these dark areas, the noise level is critical but it is almost never taken into account in the published analyzes. This work first presents the importance of compensating the instrumental noise. Then, the comparison between published POLSAR parameters clearly demonstrates the interest of the Polarization Difference (PD=VV-HH in linear unit) and shows that the usual quad-pol parameters are not optimum for oil slicks detection over maritime surface.