Modified polar format algorithm for processing spaceborne SAR data

This paper describes a modified polar format algorithm for SAR image-formation processing. The algorithm focuses raw data assuming a spherical reference surface (ground surface), and, unlike standard polar format algorithms, it assumes spherical rather than planar signal wavefronts. The algorithm, or some variant of it based on the same geometry, is therefore more suitable than the standard polar format algorithm in spaceborne applications for which there is significant curvature of the platform flight track and/or curvature of the Earth surface. The algorithm is described here in the context of spotlight-mode data acquisition.