A three-component scattering model for polarimetric SAR data

TLDR

The authors developed an approach that fits a combination of three simple scattering mechanisms to polarimetric SAR observations. The model combines canopy scatter from randomly oriented dipoles, evenor double‑bounce from orthogonal surfaces with differing dielectrics, and Bragg scatter from a moderately rough surface to represent polarimetric backscatter from natural targets. The model accurately reproduces tropical rainforest polarimetric backscatter, enables clear discrimination between flooded, nonflooded, forested, and deforested areas, and provides a predictive tool for estimating the impact of forest inundation and disturbance on radar signatures while simplifying complex scattering models.

Abstract

An approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric SAR observations. The mechanisms are canopy scatter from a cloud of randomly oriented dipoles, evenor double-bounce scatter from a pair of orthogonal surfaces with different dielectric constants and Bragg scatter from a moderately rough surface. This composite scattering model is used to describe the polarimetric backscatter from naturally occurring scatterers. The model is shown to describe the behavior of polarimetric backscatter from tropical rain forests quite well by applying it to data from NASA/Jet Propulsion Laboratory's (JPLs) airborne polarimetric synthetic aperture radar (AIRSAR) system. The model fit allows clear discrimination between flooded and nonflooded forest and between forested and deforested areas, for example. The model is also shown to be usable as a predictive tool to estimate the effects of forest inundation and disturbance on the fully polarimetric radar signature. An advantage of this model fit approach is that the scattering contributions from the three basic scattering mechanisms can be estimated for clusters of pixels in polarimetric SAR images. Furthermore, it is shown that the contributions of the three scattering mechanisms to the HH, HV, and VV backscatter can be calculated from the model fit. Finally, this model fit approach is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem.