Interferometric SAR coherence arising from the vertically-polarized electromagnetic interrogation of layered, penetrable dielectric media

Abstract

We model coherence trends in vv-polarized Interferometric Synthetic Aperture Radar (InSAR) images arising specifically from the penetration of electromagnetic (EM) waves into geophysical media. Departing from previous InSAR coherence models, we simultaneously incorporate the interacting effects (on coherence) of (i) “multi-bounce” (wave guidance) within an arbitrary number of dielectric layers, (ii) azimuthal deviation in antenna pointing, (iii) local topography, and (iv) subsurface interface and volume scatter mechanisms. Including multi-bounce phenomena, in particular, allows better understanding of chief mechanisms behind backscatter enhancement, and the resultant strong corruption of InSAR observables, arising from interrogation of strongly guiding geophysical medium layers. Moreover, modeling the subsurface guidance behavior's influence from terrain topography expands upon many previous InSAR models that assumed simpler terrain and sensor geometries. As the two key results of this paper then, we quantitatively elucidate (i) how guidance behavior in dielectric slabs can engender unbounded, diverging interferometric phase bias, as well as (ii) how terrain sloping can render sub-sections of InSAR coherence images, generated by otherwise terrain-robust sensor geometries, susceptible to guidance-related phase bias and correlation degradation.