The Analytic of Remotely Sensed Digital Image
2.2.2 The pixel's sky-scattering light illuminance on the slope aspect and its remotely sensed data value
As shown in Figure 2[2], a given pixel there have relationslhip between the pixel's sky light
Fig 2 The sky-scattering light shielded model by the surrounding terrain factors
illuminance on the slope aspect
where P
ij is shielded by the suround landform and the pixel's sky light illuminance
where P
ij is on flat and widen terrain condition as:
Where,
is the terrain-shielding angle of pixel in the Kth aspect on a digital topographic map.
is the azimuth increment.
In a similar way, there have:
2.2.3 The quantitative relationship of pixel's remotely sensed components between solar direct light and sky-scattering light illuminance
The quantitative relation between pixel's remotely sensed components of solar direct light D
ij and remotely sensed components of sky-scattering light illuminance D
ij depends on the ratio of the horizontal projective aspect component of the sky-scattering light illuminance
(E'
ij) to the solar direct light
(E'
Sij) on the pixel's slope aspect surface (What is called scatter to direct ratio(SDR)).
According to (4) and (5) equation, we have,
3 The scatter to direct ratio(SDR) and the remotely sensed data value of atmospheric path radiance (APR)
In horizontal direction, the spatial change of sky-scattering light illuminance to the solar direct light (SDR) and he remotely sensed data value of atmospheric path radiance, have such properties as low-frequency and continuousness. Thus, the horizontal component of a certain pixel point can be interpolated by digital surface simulation. According to the distance-weighted interpolation algorithm, We can get the following expression:
Where
D
AK and
L
K are seperately defined as the satellite-ground synchronous observational pixel's remotely sensed data value of APR and SDR on the =ground surface in Kth small region; And
S
k is the distance from the
Kth observation point to the pixel
The compute algorithm of the remotely sensed data value of pixel
P
k of APR is presented in
Reference
[3]:
Where,
DN
1, DN
2 respectively refers to the pixel's remotely sensed data value of two different neighboring ground features,
is their reflectivity. And n is the number of actual-measured discrete ground observation points.
