2.4.1 Optical calibration

In order to perform an optical calibration, launch the Optical calibration application (shortcut CTRL+A). We are going to use this application to perform a TOA (Top Of Atmosphere) conversion, which consists in converting the DN pixel values into spectral radiance (in W/m2/steradians/micrometers). Once the application is launched, the user must fill the required fields in (in, out, gainbias.txt -gain and bias values in a txt file-, solarillumination.txt -solar illumination values in watt/m2/micron for each band in a txt file-, and so on... refer to the documentation of the application).

In the figure below ( 2.6), by taking a look at the layer stack, one can notice that the values of the calibrated image are now expressed in spectral radiance.


PIC

Figure 2.6: Before and after calibration.