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Title
Mesures physiques et signatures en télédétection

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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