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I am having troubles with extracting data in ArcGIS buffer extractions from the MOD11A2files after processing them into GEOtiff, most of them seem fine but when looking at nightly temperature on some of my coordinates of interest my values go way below zero. Some down to -273. I have multiplied the data with 0,02 and then subtracted 273 to get them as Celsius. Is this a common problem? I can't manage to find anything about it in forums etc and unfortunately I have a tight schedule and am stressed to get the results out.

Anyone familiar with this problem?

  • Just out of curiosity, what formula is that for converting temperature? What units did you have initially? If you would've had values below -273.15 degrees Celsius, I'd say there's definitely something wrong... :) – Martin Sep 26 '13 at 6:31
  • Just using the formula specified to recalculate the value from metadata of the files. The lowest degrees were of course -273.15 degress, I suspect that these values are due to cloud cover. Could that be right? – David Nygren Oct 10 '13 at 8:50
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You could review the null values or you could consider omitting the negative values before multiplying them by the scale factor (0.02) and then subtracting it -273.15, ie, the formula (DN * 0.02) -273.15 works perfectly but some pixels in the image Have data errors so it gives the negative values. It must be remembered that the zero values must be taken into account, which must be changed to NA.

LST[LST==0]<-NA

You can see it here: https://stevemosher.wordpress.com/modis-reprojection-tool/

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