Consideration on Singular-Point Generating Mechanisms by Analyzing the Effect of Phase-and-Polarization Optimization in PolInSAR

We elucidate the generation mechanisms of singular points (SPs) by investigating the relationship between the phase distortion and the polarization-state changes in polarimetric interferometric synthetic aperture radar (PolInSAR). We find that there is a high correlation between the parameters in the Pauli coherency matrix and those in the scattering mechanism vector optimized by the maximization of interferometric coherence. It means that there is a correlation between the parameters of polarization and those of the phase compensation. In other words, the main changes in phase and those in polarization are caused by an identical phenomenon, that is, scattering itself. Therefore, we can use the parameters of polarization to reduce SPs. We also find that other origins that cause the changes in phase are the interference of waves from multiple scattering sources and thermal noise. Lastly, we investigate how the optimization compensates polarization changes by introducing the scattering sphere representation. We find that the optimization reduces randomness in the polarimetric features, and enhances the features specific to deterministic scattering such as surface and double-bounce scattering. It means that probabilistic/random scattering is the main origin of SP generation.