The pyramids of Gizeh seen by TerraSAR-X - A prime example for unexpected scattering mechanisms in SAR

Multiple scattering may render synthetic aperture radar (SAR) image interpretation difficult, particularly when it comes to imaging of man-made structures. In medium-resolution SAR images, contributions from different scattering mechanisms can only be distinguished for large objects and under favorable conditions, like bridges over calm water. Since the launches of TerraSAR-X and COSMO-SkyMed, high-resolution SAR imagery is readily available from every spot on the Earth, and multiple scattering image features will be increasingly found in many of these data. Some of the first TerraSAR-X images show the pyramids of Gizeh in a seemingly unexpected geometry. Instead of being geometrically distorted, the near-range faces of the pyramids look like ground projected. This letter explains this image puzzle by a mixture of two scattering effects. The theory is confirmed by an interferometric evaluation. The discussed image artifact can be seen as representative for many other multiple-scattering SAR imaging scenarios in high-resolution images. This letter also demonstrates once again that the interpretation of complex scattering configurations benefits from interferometric information.