A comparative study of coherence estimators for interferometric SAR image coregistration and coherent change detection

The coherent nature of the SAR imaging process opens up the opportunity to create interferometric image pairs, which carry a large amount of information about the scene. In this paper, the interferometric coherence is investigated in detail. Coherence is a measure for the temporal stability of the scene with respect to the phase information. Classically, coherence is used for the task of co-registration of the image pair, with the goal of coherence maximization, since such a co-registration will yield the most reliable interferometric phase information. The second important field of application is coherent change detection, i.e. the detection of changes in the scene that most often do not change the backscattering properties of the images and thus are not detectable in the amplitude images. For such an application it is of importance to maximize the contrast between the incoherent changed parts of the scene and the coherent surroundings. With these two applications in mind, in this paper, several published coherence estimation schemes are investigated. The different coherence estimators are applied to an airborne data set, and results regarding coherence maximization and coherence contrast maximization are shown.