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Fig. 3.19.
Dependence of spectral brightness coefficients of moose marsh upon the viewing
direction. Average values of SBC of the relevant classes and the 1 standard deviation interval
are shown:
upper curve
- the direction of the back reflection:
middle curve
-theviewing
angle, corresponding to back reflection for azimuth 135
◦
;
lower
-observationtonadirand
azimuth from 0 till 90
◦
sand has just been noted to be a back-reflecting surface (see Sect. 1.4). The
similar property is also inherent in the moss marsh (qualitative pictures of
the anisotropy for sand and marsh are close). The data in Fig. 3.19 obtained
for the marsh surface allow the estimating of the analogous SBC dependence
upontheviewingangleandazimuthforthesandsurface.TheSBCincreaseis
apparent when approaching to the point opposite to the Sun (
ϕ
=
180
◦
): their
magnitudes exceed the magnitude to the nadir in 1.5-2 times.
For the analytical description of the anisotropy the following function is
introduced:
A
1
µ
µ
ϕ
=
π
µ
µ
)
X
2
(
ϕ
ϕ
) ,
R
(
,
)
X
1
(
−
−
(3.14)
µ
ϕ
where
A
is the surface albedo, (
) is the definite certain selected direction
of the reflection namely it is the direction of the mirror reflection or the back-
reflection here,
X
1
(
,
ϕ
)arethecertainfunctionsdescribingthe
anisotropy, when the viewing angle cosine
µ
)and
X
2
(
µ
ϕ
and azimuth
of the reflection
µ
=
µ
µ
,
ϕ
=
ϕ
ϕ
.Factor
π|µ
are deviating from the selected direction:
is
appearing to co-ordinate (3.14) with expression of the albedo through the SBC
(3.11). From the same relation the normalizing conditions for the functions
−
−
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