The Landsat TM Image data that comes with zipped folder contains metadata text file in which all necessary information have been written. In order to further process that data, first DN to radiance conversion required and the method that I read from the landsat handbook Landsat 7 Handbook is as under:
L = ML * Qcal + AL where ML is band-specific radiance multiplicative factor and AL is additive factor andQcal is quantized pixed value.
and these values can be found in that metadata file. But the attached guide A Straight Forward guide for Processing Radiance and Reflectance_V_24Jul12.pdf to convert the DN to radiance table 1 shows the constant values for different period of landsat TM data.
My question here is what are these postcalibration values are and if MTL file contains the values that are different with the values in that table which values should we take for conversion of DN to reflectance.
Chander et al. 2009 have also mentioned these values in a summarize form.