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I'm using QGIS raster calculator to convert a panchromatic image of digital numbers (DNs) to radiance. The equation I need to use goes:

0.923*"15JAN12-P2AS"*(7.973540e-02/2.896000e-01)+(-1.700)

The raster DN values range from 0 to 1143, but when I apply the raster calculation above the result gives an image of NaNs and statistics as follows:

STATISTICS_MAXIMUM=-1.7000000476837

STATISTICS_MEAN=-1.7000000476837

STATISTICS_MINIMUM=-1.7000000476837

STATISTICS_STDDEV=1.2508972339943e-05

Any ideas as to why this calculation fails?

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I generated an aleatory raster (100x100) with values between 0 and 1143 ("test_panc@1") and, afterward, I copy/paste your expression at "Raster calculator expression" window where your "15JAN12-P2AS" name map was substituted by the mine ("test_panc@1"). After click in OK, I got a raster without any nan values; as it can see at below image. So, your expression is apparently correct but the map name should be something as "15JAN12-P2AS@1".

enter image description here

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  • Thanks, I ran it with the name 15JAN12-P2AS@1 and still got the same problem. However, when using the SCP (semi-automatic classification plug-in) Band Calc with the same expression as you suggest it gives me an image that looks to be correct (ranges in values from -1.7 to 290.13). Still not sure why the standard raster calculator doesn't give the correct answer though!
    – beadyeyes
    Aug 2, 2016 at 17:42

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