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layers are determined by modelling the scatterers within the layers as either discs or needles with given sizes, 
orientations, (volume) number densities and dielectric constants. Contributions to the total backscattered signal 
are either direct backscattering from the layers, interactions involving a single scatter from a layer along with 
reflection from the ground and a direct (attenuated) contribution from the ground. The ground scatter is modelled 
using standard approximations, namely the Small Perturbation Method or the Kirchhoff Scalar and Stationary 
Phase approximations, (Tsang et al 1985). An additional feature is that surfaces with a sinusoidal variation 
(such as are found in potato fields) can be modelled by deforming one of the standard approximations onto a 
sinusoidal surface. The important properties of the ground in so far as the scattering is concerned are the surface 
roughness and the dielectric constant 
To make a direct comparison between the theoretical predictions and the observed image data 
one requires a detailed set of model input data either measured directly or derived from the measured ground data. 
The model input parameters are given in Table 1 and the relevant ground parameters that were measured are 
given in Table 2. 
Soil 
Horizontal correlation length 
Vertical height standard deviation 
Volumetric moisture content 
Texture (% sand, clay, silt) 
For potatoes 
ridge height 
ridge spacing 
ridge direction 
Crop 
Crop height 
Height of each layer 
Ground coverage 
For each scatterer type 
dimensions 
orientation angle mean 
orientation angle spread 
number density 
gravimetric moisture content 
Soil 
Horizontal correlation length 
Vertical height standard deviation 
Volumetric moisture content 
Gravimetric moisture content 
For potatoes 
ridge height 
ridge spacing 
ridge direction 
Crop 
Crop height 
Height of each layer 
Ground coverage 
For leaves 
dimensions 
orientation angle mean 
orientation angle spread 
number density 
gravimetric moisture content 
For stems 
length 
number density 
gravimetric moisture content 
For wheat ears 
length 
number density 
gravimetric moisture content 
Table 1 Model Input Data 
Table 2 Ground Data Collected