Abstract: An interferometric Synthetic Aperture Radar (SAR) system having a special-purpose processor to integrate motion compensation, interferogram coregistration, and a spectral shifting for optimal interferogram correlation together to achieve efficient, accurate, and robust three-dimensional imaging. A simple radar mapping coordinate system is implemented in the present invention to enhance the overall image processing and in particular to improve the accuracy and efficiency. The present invention substantially improves the fidelity and efficiency of phase unwrapping by incorporating phase-bootstrapping process, a correlation filter, and other processes. Absolute phase determination is implemented without known ground references by two proposed techniques employing cross-correlation of sub-patches to generate a number of estimates within a patch and weighting correlation processes.