Using ArcMap 10.3, I am trying to perform map algebra on a raster with 2013 annual PRISM precipitation for the U.S. (http://prism.oregonstate.edu/recent/). The raster has 1 band an is floating point.

Using Spatial Analyst Tools > Map Algebra > Raster Calculator (i.e. not within model builder), I have tried to create a new raster by executing these expressions (separately):

"PRISM_ppt_stable_4kmM3_2013_asc.asc" * 0.1 and Float("PRISM_ppt_stable_4kmM3_2013_asc.asc" * 0.1)

Both expressions yield this error:

Raster(r"PRISM_ppt_stable_4kmM3_2013_asc.asc") * 0.1
ERROR 000539: Error running expression: rcexec() 
Traceback (most recent call last):
  File "<expression>", line 1, in <module>
  File "<string>", line 5, in rcexec
  File "c:\program files\arcgis\desktop10.3\arcpy\arcpy\sa\Functions.py", line 4333, in Times
  File "c:\program files\arcgis\desktop10.3\arcpy\arcpy\sa\Utils.py", line 53, in swapper
    result = wrapper(*args, **kwargs)
  File "c:\program files\arcgis\desktop10.3\arcpy\arcpy\sa\Functions.py", line 4330, in Wrapper
    ["Times", in_raster_or_constant1, in_raster_or_constant2])
RuntimeError: ERROR 999998: Unexpected Error.

Failed to execute (RasterCalculator).

What am I missing here?

  • 2
    Use ASCII to raster tool first
    – FelixIP
    Commented Apr 11, 2016 at 22:23
  • I agree with @FelixIP ASCII is a text file format and not what I would consider a true raster format, it's more of an "interchange" format that can be read by many software. So you need to convert it first then run your raster calculations.
    – Hornbydd
    Commented Apr 11, 2016 at 23:00

1 Answer 1


After much trial and error, I discovered there was an issue with my environment settings. Raster outputs were not set to have the same coordinate system as inputs. After I changed that, the raster calculator expressions worked fine.

  • Don't forget to accept your answer by clicking the green tick.
    – user35594
    Commented Jun 10, 2017 at 19:46

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