Converting Landsat TM and ETM+ thermal bands to temperature
The Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) sensors acquire temperature data and store this information as a digital number (DN) with a range between 0 and 255. It is possible to convert these DNs to degrees Kelvin using a two (or optionally three) step process. The first step is to convert the DNs to radiance values using the bias and gain values specific to the individual scene you are working with. An optional second step would apply an atmospheric correction using appropriate local values for several parameters, resulting in more accurate surface temperatures. The final step converts radiance data from step one, or the optional step two, into degrees Kelvin.