Interferometric Coherence Optimization: A Comparative Study

The Interferometric coherence measures the degree of similarity or the correlation between the radar signals corresponding to complex SAR images viewed from close angles. The strong dependence of the interferometric coherence to the polarization state can consider that there is a combination of polarization to achieve maximum interferometric coherence. The methods developed in this field are based on the combination of information derived from polarimetric channels of the interferometric couple and define new projection vectors that maximize the highest possible value of coherence. In this paper we investigated two interferometric coherence optimization methods. The first one is based on the selection of the best pair of projection vectors that maximizes the coherence. The corresponding algorithm leads to an eigenvectors / eigenvalues problem, where each vector represents a scattering mechanism used for view. The second method used an identical projection vector for the two images representing a unique scattering mechanism. To evaluate this work, we used a couple of interferometric airborne polarimetric data acquired on the Tapajos in Brazil, in the P band. Results compared to classical coherence reveals that both methods give better results than single acquisition, however, the first one is the best.