and the satellite 
  
Figure 1 Geometric relationship among the sun, the surface 
Satellite 
Sur face (Lambertian) 
  
  
a Levenberg Markard followed by 
simulated anneal ing. 
2.3 Physical Models 
On the other hand, the factor p 
employed physical models for the 
geometric relationship among the 
satellite, ground surface and the 
sun, the typical atmospheric effect 
described with MODTRAN-3, and the 
surface conditions that is ground 
cover target for the pixel of 
interest is forest and is followed 
by Lambert's Low(Lanbertian Surface). 
2.3.1 Geometric Relationship Among 
Inc Satellite, the Surface and the 
un 
The geometric relationship proposed 
here is shown in Figure 1 
In the figure solar zenith angle and 
azimuth angle are expressed by the 
following equation, 
cos(.X) — sin($)sin(8) 
+cos($)cos(8)cos( 4) (3) 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
sin() = -cos(8sin(A/sin(x) (4) 
where x. » ¢.8. / are solar zenith 
angle, solar azimuth angle, Latitude, 
solar latitude, and solar time angle, 
respectively. 
2.3.2 Atmospheric Transmittance 
U.S. Standard Atmosphere is assumed 
in this study. MODTRAN-3 allows us 
to calculate atmospher ic 
transmittance as a function of 
location, solar zenith angle, solar 
azimuth angle, season and so on so 
that it is applicable for 
calculation of arbitrary atmospheric 
transmittance.  Up-welling radiance 
from the atmosphere should be take 
into account. Only the atmospheric 
transmittance, however is 
considered. 
2.3.3 Surface Conditions 
In terms of surface condition, 
almost flat plane of the Lambertian 
surface is assumed in this study so 
that azimuth and elevation angles 
and nadir surface reflectivity are 
the factors for characterization of 
the surface. 
38 
        
    
     
  
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