Modelling of directional spectra in vegetation media using RET theory

Abstract

This paper aims to model the directional spectra in vegetation media using the radiative energy transfer (RET) theory. A generic propagation model (N. C. Rogers, et al., May 2002), developed for the United Kingdom Radiocommunications Agency (formerly RA, now a subsidiary of OFCOM), concentrated on the results of previous work (R. Johnson, and F. Schwering, 1985) which suggested that there are several possible mechanisms of propagation associated with vegetation. Each component is modelled using simple methods, such that the final model can be easily implemented. The scattered component is modelled using the radiative energy transfer theory (RET), as this is a fully deterministic model which may be used by fitting the model input parameters to the specific measurement geometries and then expanded to provide results for more generic cases. This paper concentrates on improving the method of extracting the RET input parameters for the scattered component of the generic propagation model. An improved method to extract these input parameters is presented. The results obtained from measurements performed in a Southern European forest formed by Populus trees are used to assess the performance of the model