I am using my own atmospheric correction method to determine bottom of atmosphere radiance of Worldview 2 data, and want to apply the radiometric calibration tool to convert the resulting image to BOA reflectances using the equation (pi.L.d^2)/(Esun.sin(theta)) as provided in the ENVI documentation. My routines remove much of the original metadata that came with the imagery. That documentation states "If the input file does not contain metadata for reflectance gains and offsets, ENVI computes TOA reflectance using the following equation:" That apparently isn't true. First I have to force the meta data to include radiance Gains and offsets so the tool works at all. Then I have to provide dummy reflectance gains and offsets to allow for the reflectance option in the drop down menu of the tool (setting the gains to 1, and the offsets to 0). I also reset the TOA Irradiance values for each band. This ends up with the same data as the input image, leading me to conclude the tool is not applying the equation. A couple of questions:
1) Is the documentation correct?
2) Is there a way to force the tool to apply the reflectance equation?
3) Where does ENVI get the earth-sun distance from (assuming an image input starting point of DNs and the original metadata)?
4) Is there a simple solution to deriving BOA reflectance from BOA radiances (or said another way: to apply the reflectance equation to any input image?)