Multi-base INSAR with enhanced signal processing

Abstract

Synthetic aperture radar interferometer provides three-dimensional information by using the phase as an information source. An interferogram contains the amplitude as well as the phase information of a SAR image pair. The resultant phase of the interferogram is only measured modulo 2π. To calculate the elevation of each point it is necessary to add the correct integer number of phase cycles to each phase measurement. The problem of solving this 2π-ambiguity is called phase unwrapping. On the one hand decrease of the interferometer's carrier frequency causes larger altitude variation which can be resolved without ambiguity. However, on the other hand decrease of carrier frequency causes decrease of accuracy of the relief altitude estimation. This contradiction may be resolved for example in the multi-frequency interferometric system, but it is expensive. This paper presents a method for the phase-ambiguity resolution in the two-frequency interferometer. By multiplying signals with different carrier frequency, it is possible to resolve phase-ambiguity as well as provide high-precision of relief altitude estimation. This work presents an analytic equation for the errors in the InSAR, for the carrier frequency calculation. The modeled results show accurate relief estimation as well as phase ambiguity resolution.