Ship Detection, Discrimination, and Motion Estimation via Spaceborne Polarimetric SAR-GMTI

A new approach to ship detection, discrimination, and motion estimation is proposed and demonstrated using a combined polarimetry and GMTI technique from a spaceborne platform. Using a standard dual-pol SAR, the new method exploits a bright “shadow” in cross-pol imagery of a moving ship and its azimuth-shifted image to discriminate it from other stationary or quasi-stationary objects (e.g., icebergs) on the ocean surface and to estimate its motion parameters, such as radial speed and heading. The motion estimation results are compared to those obtained using the newly implemented Dual-Channel Polarimeric GMTI modes on RADARSAT-2. Unlike the ship wake approach, the proposed technique is applicable to and successfully demonstrated for both C-band and X-band radars (RADARSAT-2 and TerraSAR-X) and it is not dependent on the angle of incidence to achieve a good signal-to-clutter ratio and ship detectability. Physical mechanisms giving rise to ship “shadows” are also discussed.