Strange values converting Landsat Band 6 to LST

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Last Post 09 Dec 2013 05:00 AM by anon

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anon

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09 Dec 2013 05:00 AM
Hi-- I'm trying to convert Landsat data into land surface temperatures (I have ENVI 4.5) --having trouble opening from the .met files but I'm using the Band 6 Geotiff which looks fine. However, when I run the Landsat Tm calibration utility, I'm getting values like 0.22. Since I believe the values are supposed to be in degrees Kelvin, I know I'm doing something wrong but can't figure out what? There aren't too many parameters to set--the date/solar elevation angle are correct, and I've taken the min/max scale values from the following lines in the metadata file: RADIANCE_MAXIMUM_BAND_6 = 15.303 RADIANCE_MINIMUM_BAND_6 = 1.238 I've also selected 'reflectance'. Is this the incorrect setting, or am I missing a few steps to get the accurate LSTs in Kelvin? Thanks-- --s

MariM

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09 Dec 2013 08:21 AM
There were some issues with the old Landsat calibration of geotiff data. The metadata was not supported at that time and ENVI used hard-coded values for calibrating geotiff files. Those values could very well be out of date if you have downloaded recent data since the calibration values have been updated over the years. You would be better off applying the equation manually using Band Math or updating to the latest version of ENVI that supports the reading and application of the metadata values.

Deleted User

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23 Jan 2014 07:16 PM
Steve, I know this was posted a while ago, but for future reference you convert Band 6 to radiance and then you apply the inverse of the Plank function to derive degrees Kelvin. The band math expression: K2 / alog(((K1 * 0.95) / B1) + 1) K1 and K2 being the calibration constants for the thermal infrared band ( see metadata for the correct values).

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