iiance ratio 
and now the 
iiscussed in 
i refractive 
i of the wax 
presence of 
eaf. In the 
:n accounted 
T parameter 
reasonable 
our of this 
R model its 
i determines 
ie tabulated 
of specular 
additional 
ection from 
(5) 
he PROSPECT 
L, k = 0.1. 
parameters 
.eaf; 
.ce wax and 
or i = 1 
1 is rather 
o versatile 
are rather 
2 m must be 
ers are the 
indices c , 
otor (3, tfie 
ind optical 
the model. 
In Fig. 1 we note the corn leaf reflectance and transmittance spectra and the soil 
reflectance spectrum measured by Ranson et al. (1985) along with model calculations 
using the PROSPECT model (Jacquemoud and Baret, 1990) and Price's (1990) basis 
functions, respectively. 
Figure 1. Spectral reflectance (x) and transmittance (+) of corn leaves and 
soil reflectance (A) by Ranson et al. (1985) compared with model 
calculations. The parameter values are given in Table 1. 
Figure 2 shows the leaf inclination distribution of corn canopy measured by 
Ranson et al. (1985), and the solid line shows the elliptical distribution that 
approximates the measured one. 
The Angstrom turbidity factor 3 can be estimated from the measured diffuse 
to total irradiance ratio D^yo^ at least in one spectral channel. Then 
3 -- 
t(A) 
A' x 
( 6 ) 
>- 
I- 
Figure 2. Inclination distribution 
density of corn leaves measured by 
Ranson et al. (1985) and the best fit 
of the measured data with elliptical 
distribution (the solid line). 
where 
t(A) = [D X /Q X 
Figure 3. Direct to total irradiance 
ratio (*) measured by Ranson et al. 
(1985) compared with model calculations 
( )• 
oq(A)] /r( A) , (7) 
695