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I have a D.E.M. that has values between -1.13 and 23.33. In the Symbology, I changed the Stretch Type to Minimum-Maximum to get the true values and those previous values are what the raster draws. I wanted to eliminate negative values and found other questions that dealt with getting rid of negative values. One answer said use SetNull(raster <0, raster). I also tried Con. The output from these operations create new files with increased max values. When I used Con, the max went to 64.01 and when I used SetNull, the max increased to 43.4. I don't know why this is happening. The raster is a 32 Bit floating point Tiff.

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    Do the cells match up (i.e. visually line up)? and are they the exact same cell size? I suspect you have some unset (or badly set) environment settings. – jbchurchill Nov 10 '16 at 17:05
  • @jbchurchill, yes, the cells match up and they are the same exact size. I don't know what environment settings to check. – shea Nov 10 '16 at 18:01
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    How are you ascertaining the min/max values? ArcGIS often uses a sample for deriving the raster statistics. If you open ArcCatalog, right click on the raster and select "Calculate Statistics", make sure the skip values are set to 1 and run the tool. Then, right-click on raster again and select "Properties". This will tell you the actual statistics of the raster. Do this for the original and new rasters to see if the new max is, in fact, incorrect. – Jeffrey Evans Nov 10 '16 at 21:13
  • Statistics of all kinds have been notoriously unreliable in ESRI software. Search our site for examples. – whuber Nov 10 '16 at 21:19
  • Deleting and recalculating the statistics seems like a good idea. If you are working in a geodatabase you might try making a standalone file as well. Possibly the process is resampling for some reason you are not thinking of. Check in ArcMap Advanced Setting Utility (should be in the Utilities subfolder in ArcMaps install location) and check in the "Raster" tab that you are using Nearest Neighbor... although how it would be getting values that much above the apparent max is a bit unclear to me.. but I have read that this happens. – Mike Nov 10 '16 at 21:54

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