Application of volumetric multiple scattering approximations to foliage media

Abstract

Vegetation media may be viewed as two or more different types of dielectric scatterers arranged in a random geometric configuration in a surrounding “host” medium. This allows the vegetation to be treated as a continuous medium where the propagation of the waves through that medium is governed by an effective dielectric constant, (ε*). In this paper, several multiple scattering approximation techniques were used to quantitatively estimate the values of the effective dielectric constants for vegetation media based on the foliage density and dielectric properties of the scattering elements composing the vegetation. Because this formalism is not computationally intensive, it is useful for modeling the propagation losses experienced by an electromagnetic wave propagating through vegetation media in electromagnetic scattering or radar simulations. The theoretical approximations of ε* are compared with data at three levels. First, the calculated values of ε* were compared with values reported in the literature. Second, the effective dielectric constants for a foliage environment were used to calculate attenuation coefficients of coherent waves propagating through dense vegetation. The calculated attenuation constants were compared with experimental measurements reported by various authors at frequencies between 50 MHz and 3.2 GHz, resulting in good agreement. Finally, the values of ε* were incorporated into a bistatic scattering model which was used to calculate an effective normalized scattering cross section σ0 for a grass‐ and forest‐covered terrain. This was compared with L band data resulting in excellent agreement between theory and experimental data.

Radio wave propagation through vegetation: Factors influencing signal attenuation

“…The lack of extensive measurement campaigns to aid and verify model development means that empirical models have, historically, been based on small amounts of narrowband data and are often biased towards artifacts at the measurement site [ Vogel and Goldhirsh , 1993; Seville and Craig , 1995; Al‐Nuaimi and Stephens , 1998]. Analytical methods used to model radiowave propagation through vegetation often either grossly over‐simplify the vegetation medium or require the use of numerical analysis to provide solutions to intractable formulations [ Brown and Curry , 1982; Tavakoli et al , 1991; Tamasanis , 1992; Rikte et al , 2001].…”

Microwave radiometry of vegetation canopies

“…In the continuous model, a vegetation canopy is considered as a uniform medium whose electrodynamic characteristics are described by the effective dielectric permittivity ef ε or by the effective permittivity tensor ef εˆ (Allen and Ulaby, 1989;Chukhlantsev, 1988;Du and Peake, 1969); Fung and Fung, 1977;Fung and Ulaby, 1978;Fung, 1979;Milshin and Grankov, 2000;Redkin et al, 1973;Redkin and Klochko, 1977;Tamasanis, 1992;Tsang and Kong, 1981;Ulaby and Bush, 1976). To determine ef εˆ, Allen and Ulaby (1989), Redkin et al (1973), and Redkin and Klochko (1977) used the formulas for a mixture of dielectrics obtained in the electrostatic approach.…”

“…To determine ef εˆ, Allen and Ulaby (1989), Redkin et al (1973), and Redkin and Klochko (1977) used the formulas for a mixture of dielectrics obtained in the electrostatic approach. In Du and Peake (1969) and Tamasanis (1992), the continuous medium concept was applied to determine the radio wave attenuation by foliage. The wave corrections to the effective permittivity were obtained in Fung and Fung (1977), Fung and Ulaby (1978), and Fung (1979) on the basis of the small perturbation theory.…”

“…For wheat and soybean, the effective dielectric constant was calculated in Allen and Ulaby (1989), and for corn leaves, in . Tamasanis (1992) reported the effective dielectric constant of foliage calculated in the approximation of spherical inhomogeneities. In Kerr and Wigneron (1994), the effective dielectric constant of vegetation was modeled by the expression…”

The Use of Multiple-Polarization Data in Foliage Penetrating (FOPEN) Synthetic Aperture Radar (SAR) Applications

“…Foliage attenuation increases significantly with frequency [13][36] [41]. Two-way HHpolarization signal attenuation reported in [13] for a 30° depression angle increases from 5.5 dB at UHF to 17.0 dB at L band and to 33.6 dB at C band.…”