[UW-GIS-L] floating point raster map algebra / raster calculator problem

[Jeremy Littell]

I've searched for help on this in the archives and didn't find  
anything, but that may be because I'm not characterizing the problem  
accurately. Any help would be appreciated.

I'm running ArcMap 9.3 on Windows XP inside a virtual machine (Fusion  
on a Mac OSX 10.5). It has worked fine in the past.

The problem goes like this:

I import several ascii grids to floating point rasters, either command  
line or using the conversion toolbox. They are the same domain, same  
grid - all that varies is the data values. They import and display  
fine and the data values are all plausible, although in the properties  
tab under "source", I see that the NoData value = -3.4028235e+038 when  
I thought it should be -9999.

When I try to do any operations on multiple grids, e.g. [grid1] -  
[grid2] , I end up with a raster that has 0 and 1 values even though  
the original data is numeric, floating point, from 0 to 2400.9 or so.  
That NoData value seems like the culprit, but I need to know where  
it's coming from so I can fix it. I want to automate this because I've  
got several hundred such grids to convert and do operations on.

Thanks for any insight.

JL


~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jeremy S. Littell
Research Scientist
CSES Climate Impacts Group
Box 355672
University of Washington
Seattle, WA 98195-5672
P: 206 221 2997
Email: jlittell at u.washington.edu
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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