The rational polynomial coefficient (RPC) model has raised considerable interest in the photogrammetry and remote sensing community. Much work has been done on frame camera imagery and/or push-broom scanner imagery, and it has been widely accepted that the RPC model can be taken as an alternative to rigorous sensor models for photogrammetric processing. However, there have been few publications discussing the application of the RPC model to SAR image processing. In this paper, we first review the geometric effects of SAR imagery and compare SAR imagery with optical satellite imagery. Then, the unbiased RPC estimators for a series of SAR images are derived. Based on numerous tests with the rigorous sensor model available, the modeling error of the RPC is analyzed. This study found that the RPC model is suitable for SAR imagery and can be used as a replacement for the rigorous sensor model for photogrammetric processing.