Cardinal Effect in Bistatic SAR Imagery: Analysis and Physical Interpretation

This paper is aimed at supporting the analysis and interpretation of bistatic synthetic aperture radar (SAR) images, which are available by now through the Capella constellation or will be soon available thanks to the upcoming PLATiNO-1 mission. More specifically, here we focus on urban areas, where the so-called cardinal effect dominates the backscattering in conventional monostatic SAR imagery. Such effect is also evident in bistatic acquisition geometries, as it has been recently demonstrated, even if with different dynamics. Through the application of analytical models for the electromagnetic scattering from buildings in bistatic geometries, we provide a physical explanation of the SAR image formation in the urban environment and in arbitrary acquisition geometries. We quantitatively evaluate the contrast between the returns from the building and the surrounding terrain under different roughness regimes and imaging geometries. The analyses provided here might support a correct human interpretation and automatic processing of urban bistatic SAR images.