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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