An experiment has been carried out with simultaneous Synthetic Aperture Radar (SAR) imaging of ships in harbour from the satellite-based system TerraSAR-X and the small helicopter-based radar PicoSAR. The targets are two large passenger vessels. The data sets are well suited for studying the results of different radar parameters and imaging geometries, in particular different resolution, azimuth angle and elevation angle. The imaging geometry plays an important role for the appearance of the ships in the SAR images. In satellite images from a high elevation angle the layover makes the silhouettes of the ships visible. The silhouette can be used as a feature for target recognition and be compared with a reference set of silhouettes produced from 3D models. Experimental results demonstrate a potential for ship recognition from TerraSAR-X images following this approach. With low elevation angle typical for an airborne system, top-view projections of the targets appear in the images, and the silhouette can not be used as a feature. Analysis of the high-resolution PicoSAR images reveals the importance of relatively small structures in the radar signatures. An example is the poles in the railings, which give a significant contribution to the total backscattering. It is therefore natural to assume that a reference set for target recognition based on scatterer positions should include the scattering from such structures.
