Research Methodology - Historical Land Use/Land Cover Classification Using Remote Sensing - page 73

ATCOR-2/Main Menu:
-Determining the input parameters.
- First definition (assumption) of the
atmospheric model, the calibration file, and the
visibility.

Constant atmosphere:
-Elimination of haze.
- Calculation of the reflection.

Spatially varying atmosphere:
-Elimination tof haze.
- Calculation of spatially varying
visibility.
- Calculation of the reflection.

Sun-position calculator:
- Calculate the (zenith and azimuth) of the sun at
the recording time for the given location.

Spectra:
-Interactive process to selest (adequate
atmosphere models, calibration file, and ground
visibility).
- Control the above selection by selecting typical
test object in the image.

Spatially varying atmosphere
(ext. Visibility file):
-Elimination of haze.
- Calculation of the reflection
using external visibility files.

Fig. 5.6 ATCOR-2 and its central sub-modules (Source modified from Leica Geosystems 2005 )

of other digital image processing software such as ENVI and PCI-Geomatica, or as
an independent program.
Some of its advantages are: (1) short times required for computing process; (2)
adequate results in comparison to other simple approaches or models; (3) it is easy
to get the required parameters to be input to the program; and (4) it is uncom-
plicated to set and modify these parameters separately across the study area,
especially if this area is large enough to have different radiation effects (Leica
Geosystems 2005 ). Figure 5.6 subdivides the module ATCOR-2 into many sub-
modules.
The parameters that have to be entered in the ATCOR-2/main menu are: (1) the
image has to be corrected, the input-file source location, and the output-file des-
tination after finishing the process of correction; (2) selection of spectral bands to
be corrected; (3) determining the sensor specifications (calibration file); (4)
determining the atmospheric model (based on meteorological information and the
parameters of the applied model); (5) the size of the study area; (6) size of the used
filter (to minimize the blooming effect), reflection- and emission- correction fac-
tors using the maximal dynamic range of the output-file by rescaling 8 bit; (7)
some secondary information (e.g., location coordinates, recording date/time, mean
elevation, air pressure, air temperature, absolute and relative humidity, and visi-
bility); and (8) selection of the suitable atmospheric conditions from constant and
spatially varying by comparison with secondary sources (Leica Geosystems 2005 ).
The Spectra-module can be used optionally after point 7 as parameter number 8 in
the module (main menu), checks whether the selected atmospheric model and the
visibility are adequate (and if necessary adjusts the parameters iteratively).