Evaluation of Radarsat-2 for ship detection

Ship detection and monitoring has become one of the first operational services from civilian spaceborne Synthetic Aperture Radar (SAR) satellites. The Norwegian Coast Guard presently uses such data to support fisheries monitoring in the High North. This report presents the Canadian SAR satellite RADARSAT-2, its capabilities and the possibilities to use it over Norwegian waters. Research on RADARSAT-2 SAR images is presented in the report. The dual-polarised ScanSAR mode and the full-polarised Standard QuadPol mode on RADARSAT-2 provide a novel capability to extend the range of useful incidence angles for ship detection. At low incidence angles, cross-polarised images provide much improved ship to sea contrast ratios, compared to conventional co-polarised images for low incidence angles. With RADARSAT-1 the user had to order images with high incidence angle when only co-polaisation images were available. Using cross-polarised data in one channel and co-polarised data in the second, one may obtain combinations of high contrast ship to sea images in one polarisation channel (cross-polarisation) also for low incidence angles, as well as useful images of ship wakes and other oceanographic phenomena in the second polarisation channel (co-polarisation). The two channels can also be combined to enhance the ship to sea contrast. Quad-polarised data can be used where the location to the ships are well known since the swath width is smaller. Then it is possible to analyse the backscattering from all polarisation channels and also combining the different polarisation channels for better ship to sea contrast.