FAQ

How are Radiances calculated?

The values given for GAIN and BIAS in the header are not the GAIN and BIAS as expected. These values are L_min and L_max, given in units of mW/(cm*cm)/str/micron, where BIAS is L_min and GAIN is L_max.

           D
L_rad = -------  * ( L_max - L_min ) + L_min
         G_max

where:
    L_rad is the radiance
    G_max = (2 ^ Q) - 1
            Exception: G_max = 255 for IRS-1C and IRS-1D radiometrically corrected and higher level products.
    L_max is the maximum saturation radiance
    L_min is the minimum saturation radiance
    D     is the DN from the image
    Q     is the number of quantisation bits of the sensor