A 3-COMPONENT SCATTERING MODEL FOR POLARIMETRIC SAR DATA

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, even-or double-bounce scatter from a pair of orthogonal surfa ces with different dielectric constants and Bragg scatter from a moder ately rough surface, This composite scattering model is used to descri be the polarimetric backscatter from naturally occurring scatterers. T he model is shown to describe the behavior of polarimetric backscatter from tropical rain forests quite well by applying it to data from NAS A/Jet Propulsion Laboratory's (JPL's) airborne polarimetric synthetic aperture radar (AIRSAR) system. The model fit allows clear discriminat ion between flooded and nonflooded forest and between forested and def orested areas, for example. The model is also shown to be usable as a predictive tool to estimate the effects of forest inundation and distu rbance on the fully polarimetric radar signature. An advantage of this model fit approach is that the scattering contributions from the thre e basic scattering mechanisms can be estimated for clusters of pixels in polarimetric SAR images, Furthermore, it is shown that the contribu tions of the three scattering mechanisms to the HH, HV, and VV backsca tter can be calculated from the model fit. Finally, this model fit app roach is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering prob lem.