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Last Post 20 Apr 2010 11:18 AM by  anon
Landsat data processing from USGS
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anon



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20 Apr 2010 11:18 AM
    What is the exact procedure of Landsat TM (ETM) images processing downloaded from the USGS in ENVI 4.6? I was trying to: 1) assigh the wave lenghts, gains ,offset valus via the header editor, 2) use the Basic tools - Preprocesing - Calibration utilities - Landsat TM, 3)stack the single bands and convert to BIL for further processing. But I got negative values in area where should be no data/0 values - edge of the image (where the original images with DN are 0). Thanks for help.

    MariM



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    20 Apr 2010 12:08 PM
    I would suggest you contact ITT  Technical Support and get the ENVI 4.6 patch for Landsat calibration.  This allows you to import the Geotiff images with the metadata file (_MTL.txt) and uses the updated calibration coefficents to calibrate the data.  It also masks the background 0 values now, which it did not before.  So this is what you are seeing when you calibrate your data.  The 0s in the data are not treated differently than any other pixels and 0 is a valid value, so the calibration is applied to those pixels too, which converts them to a non-0 value.  You can just mask these pixels out using ENVI's masking tool since they should all be the same value.
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