Absolute phase retrieval in a three-element synthetic aperture radar interferometer

We introduce a three-antenna SAR interferometer for topographic mapping and a statistically optimal technique for absolute phase (and hence terrain height) retrieval. This method involves taking advantage of the baseline diversity to obtain a non-aliased (i.e. not modulo 2π) phase estimate. The accuracy of the new technique is compared to the basic interferometry. Simulated results show that the unambiguous phase can be determined on a pixel to pixel basis and without sacrificing the estimation accuracy, for the usual values of the system parameters. In this new framework the phase unwrapping process of conventional (modulo 2π) two-antenna SAR interferometry can be eliminated or simplified. So, ground reference points can be no more necessary, real time processing can be performed, and phase aliasing problems in steep areas, that degrade height estimation in conventional SAR interferometry, can be eliminated. Finally this new framework may facilitate the introduction of computationally and statistically efficient 2-D estimators for smoothing or interpolation of the absolute height measures