A Monte Carlo coherent scattering model for forest canopies using fractal-generated trees

A coherent scattering model for tree canopies based on a Monte Carlo simula tion of scattering from fractal-generated trees is developed and verified i n this paper. In contrast to incoherent models, the present model calculate s the coherent backscatter from forest canopies composed of realistic tree structures, where the relative phase information from individual scatterers is preserved. Computer generation of tree architectures faithful to the re al stand is achieved by employing fractal concepts and Linden-mayer systems as well as incorporating the in situ measured data, The electromagnetic sc attering problem is treated by considering the tree structure as a cluster of scatterers composed of cylinders (trunks and branches) and disks (leaves ) above an arbitrary tilted plane (ground), Using the single scattering app roximation, the total scattered field is obtained from the coherent additio n of the individual scattering from each scatterer illuminated by a mean fi eld. Foldy's approximation is invoked to calculate the mean field within th e forest canopy that is modeled as a multilayer inhomogeneous medium. Backs catter statistics are acquired via a Monte Carlo simulation over a large nu mber of realizations. The accuracy of the model is verified using the measu red data acquired by a multifrequency and multipolarization synthetic apert ure radar (SAR) [Spaceshuttle Imaging Radar-C (SIR-C)] from a maple stand a t many incidence angles. A sensitivity analysis shows that the ground tilt angle and the tree structure may significantly affect the polarimetric rada r response, especially at lower frequencies.