Evaluation of the quad-polarimetric Radarsat-2 observations for the wetland InSAR application

Wetland interferometric synthetic aperture radar (InSAR) has been successfully applied to observe phase variations related to water level changes in aquatic environments with emergent vegetation. In this study, we evaluate the quadrant polarimetric Radarsat-2 (C-band) observations for the wetland InSAR applications by testing two datasets acquired over south Florida's Everglades wetlands. The first set was acquired over our northern study area, consisting of mostly managed wetlands and agricultural environments. The second set was acquired over our southern study area, consisting of naturally flowing fresh- and salt-water wetlands in the southern Everglades. In both sets, observations were acquired every repeat orbit (24 days) to generate interferograms with short temporal baselines that can maintain high coherence levels. Our results showed high coherence values in all polarization modes (from 0.26 to 0.42), with highest values in HH, then VV, and lowest in HV or VH. Surprisingly, all the quadrant polarimetric interferograms showed very similar fringe patterns regardless of the polarization type, suggesting that water level changes can be detected in all polarizations. Furthermore, the observations implied that double bounce is the dominant scattering mechanism, even in cross polarization (HV and VH), and not volume scattering as commonly assumed.