The atcor\cal\ folder of your CATALYST Professional installation folder contains samples of standard-calibration files for each sensor supported by the atmospheric-correction workflows. Each row in a calibration file lists the calibration coefficients for each sensor band. Bands are listed in increasing order of wavelength.
When you complete an atmospheric-correction workflow, you can use one of the standard-calibration files. If your correction is not producing the results you expect, compare the calibration coefficients (gain and bias values) in the metadata file of your data to those in the calibration file. If the values differ significantly, you can create your own calibration file specific to your data.
The calibration file contains a table of the bands, the gain value (c1 or A) and the bias (c0) value for each band. The atmospheric-correction workflows use mW/cm-2 sr-1 micron-1 as the radiance unit for each band. Because the sensors can use a different radiance unit, you may need to convert the values.
For example, some calibration coefficients are measured in W m-2 sr-1 micron-1. To convert it to the ATCOR-radiance value, multiply the values in the metadata file by 0.1.
To edit an existing calibration file to create a new one
- Open a standard-calibration file for the sensor appropriate to your data. Standard-calibration files are located in the atcor\cal folder of your CATALYST Professional installation.
- Open the metadata file that came with your data.
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If necessary, convert the values from the metadata file to ATCOR-radiance units:
- mW/cm-2 sr-1 micron-1
- Replace the bias and gain values for each band with the converted values from the metadata file.
- Save the calibration file as a new one with a .cal file name extension in the atcor\cal folder of the relevant sensor.