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Electromagnetic scattering from Foliage and vegetation: Modelling and applications in active microwave Remote Sensing

ACRS 1997

Forestry

Electromagnetic Scattering from Foliage and Vegetation:
Modelling and applications in Active Microwave Remote Sensing

H.T. Chuah

Faculty of Engineering
Universiti of Engineering
Jalan Ayer Keroh lama
75450 Melaka
Tel: +606-2523456; FaxL +606-2316552
E-mail: [email protected]


Abstract

This paper aims to review some theoretical models for electromagnetic wave-matter scattering and propagation in foliage and vegetation that have been developed for the past ten years or so. These include models using the Renormalization Technique (a field approach); the Radiative Transfer Theory (an energy/intensity approach) and models using the Monte Carlo technique (a statistical method). Various examples are given to illustrate the potentials of these methods: study of propagation of wave in a vegetation canopy to calculate the effective attenuation coefficient, and radar backscatter from a vegetation field/forest stand. The simulated results are compared with experimental data wherever possible to validata the models.


Introduction

Electromagnetic scattering and propagation in foliage and vegetation is a complex vector problem because of the multiple scattering between a mixture of randomly distributed components of the medium, including the ground surface. The task of modeling a complete vegetation medium must include all the interactions between the separate components of the vegetation, including the soil. Various volume and scattering theories have been developed for modeling the scattering and propagation in such random media [1]. Basically, there are three main approaches: the field approach, the energy/intensity approach and the statistical approach. In the past ten years, some research work has been done in Malaysia to develop models based on such formulation. This paper aims to give an overview of those models developed, together with some results and comparisons with experimental data.


2. High-order Renormalization Method (HRM)

In this field approach, the vegetation medium is characterized by a complex permittivity function:

e(r) –
ea +
ef (r) …(1)

where
ea and
ef are the average and fluctuations of the complex permittivity of the random medium. The vector wave equation for the electric field E in the medium is then written as:

(