687 
To illustrate the possibility of the model, Fig-4 shows a polar plot of the bidirectional reflectance factor in the 
case of a planophile canopy exhibiting a hot-spot effect It is seen that the typical behavior and the main features 
depicted by the field of bidirectional reflectance can potentially be reproduced following the above physical 
development. 
The bidirectional reflectance factor is plotted (for the most unfavourable conditions) on Fig-5, for different leaf 
angle distributions, solar zenith angles, leaf area indices (Lj), soil albedos (Rs) and leaf optical properties (r^ and 
tj^). These plots also show the results given by two other models proposed by (1) Myneni & Asrar [1993] and 
(2) Nilson & Kuusk [1989]. The above comparison doesn't include the hot-spot representation for any of these 
models. The relative difference (in %) with respect to the DOM [100 * (p - PDOM^ 1 PDOM^ is vef y sma11 in 
the red region for both Nilson & Kuusk and Iaquinta & Pinty models, but, in the near infrared, some larger 
differences appear which are due to the assumption made for estimating the contribution of multiple scattering. 
However, our model generally provides slightly better results, as compared to Nilson & Kuusk's model, for any 
value of leaf area index and soil albedo. The above statement is illustrated by a comparison of the models in 
terms of albedo (Table-1). 
Principol plone 
80 60 (0) 20 0 20 (F) 60 80 
Viewing ongle (degreos) 
Principol plone 
80 60 (8) 20 0 20 (F) 60 80 
Viewing angle (degrees) 
Principol plane 
80 60 (B) 20 0 20 (F) 60 80 
Viewing ongle (degrees) 
Principol plane 
80 60 (B) 20 0 20 (F) 60 80 
Viewing angle (degrees) 
80 60 (B) 20 0 20 (F) 60 80 
Viewing angle (degreos) 
80 60 (B) 20 0 20 (F) 60 80 
Viewing angle (degrees) 
K 20 
Xi37 
8 ’5 
1 10 
t 5 
o 0 
-C 
\ 
\\ 
\ ^ 
80 60 (B) 20 0 20 (F) 60 80 
Viewing angle (degrees) 
80 60 (B) 20 0 20 (F) 60 80 
Viewing ongle (degrees) 
(a) 
Erectophile 
solar zenith angle of 5° 
Lp=8. 
Rs=0.075 
1^=0.0609 & t L =0.0429 
(b) 
Erectophile 
solar zenith angle of 30° 
Ly=3. 
Rs=0.2 
1^=0.0609 & t L =0.0429 
(0 
Erectophile 
solar zenith angle of 30° 
Lj=3. 
Rs=0.15 
1^=0.4357 & t L =0.5089 
(d) 
Uniform 
solar zenith angle of 30° 
Ly=l. 
Rs=0.35 
1^=0.4357 & t L =0.5089 
Fig-5: Comparison between Myneni & Asrar (solid line), Nilson & Kuusk (broken line) and Iaquinta & Pinty 
(dotted line) models. 
(a) 
(b) 
(c) 
(d) 
Myneni & Asrar 
0.0182 
0.0254 
0.4034 
0.4012 
Nilson & Kuusk 
0.0184 
0.0252 
0.4460 
0.4406 
Iaquinta & Pinty 
0.0183 
0.0256 
0.4138 
0.4061 
Table-1: Albedo for the different models, in the 4 configurations described in Fig-5. 
3 - INVERSION SCHEME