I'm attempting to calculate land surface temperature (LST) from Landsat 7. Band 6, the thermal band for Landsat 7, comes in high gain and low gain settings. I'm calculating the temperature for Los Angeles in summer 2000 using ArcMap 10.2.2.
I know that the low gain setting (band 6L or 61) is good for scenes with high surface brightness, such as deserts. The low gain has a useful temperature range of 130-350 K. The high gain setting (band 6H or 62) is good for scenes with low surface brightness (such as those that are fully vegetated) and has a useful temperature range of 240-320 K.
I'm not sure what constitutes low and high surface brightness, relatively speaking, and whether an urban environment would count as "low" or "high" brightness. As well, I calculated LST from Landsat 5 for the same month as the one where I'm trying to calculate LST from Landsat 7, and got a high temperature above 320 Kelvin.
Due to the high temperature I got from Landsat 5 for the same scene and for close to the same day I'm leaning towards using the low gain band for Landsat 7.
Is this a correct way to think about this, or is there a better way to to choose between high-gain and low-gain for Landsat 7?