PolSARproSimPlus: Coherent Electromagnetic Simulator for Radar Scattering from Forests

About this technology

Overview

PolSARproSim features the computation of SAR backscatter images from a region with three types of scattering objects: a bare surface, an isotropic layer of short vegetation and individual trees. The software considers only directly scattered radar returns from the bare surface, while both the trees and short vegetation are assumed to include both the direct and double bounce scattering mechanisms. Trees are represented and stored in parametric form and realized using procedures coded according to chosen tree species dependent upon chosen tree heights through allometric equations. The SAR image calculation phase is broken down into stages. The first of these is the calculation of canopy tree crown and understory permittivities. Crowns are assumed to have the same mean permittivity, and to be statistically isotropic. The next stage is to construct attenuation grids, which supply look-up tables for attenuation by spatial location. The attenuation grids are used when calculating scattering to provide approximate estimates of attenuation. Having determined the attenuation grids the next stage is the calculation of SAR images themselves. To simulate direct ground scattering, the ground surface is divided into numerous facets, and these are assigned complex scattering amplitudes, and focused in the image one after the other, each being scaled by the attenuation estimate for its location in the scene. For both the direct and indirect scattering from trees and short vegetation, each plant element realization is divided into scattering elements, where each scattering element is treated as an oriented cylinder. The scattered field from each cylinder, scaled by an appropriate attenuation estimate, is accumulated into the corresponding SAR image pixel using a system point-spread function.