jevans02

Zonalsum problem

Discussion created by jevans02 on Jun 17, 2010
I have a binary grid that I want a zonalsum for. When I run zonal statistics in ArcMap Spatial Analyst using the menu option, the zonal statistics tool in ArcToolbox or in zonalsum in raster calculator I am getting the same incorrect results. I am getting large values in areas that are entirely 0 (should sum to 0). I have tried this with both the data and nodata flags. My zonal grid is 59.5MB (3.07GB uncompressed) (row/col dimensions are 32176/51272 at 90m with 41603 unique zonal values). The binary grids are the same dimensions but only ~26MB (1.7GB uncompressed). If I change the extent and subset down to the area that I am getting erroneous values for, I am getting the correct answer so it seems to be a large grid issue (again). It seems like ArcMap often yields incorrect answers with very large grids. I WOULD RATHER GET NO ANSWER THEN THE INCORRECT ONE! Unfortunately, this will not run in Workstation ArcInfo (I get a MSEEK error).

What I actually want is if the binary grid has > 5 cells with a value of 1 in a zone assign 1 else 0. 
CON(ZONALSUM(zonegrd, grd) >= 5, 1, 0)

Since I am working with 1200+ binary grids, I would like to avoid breaking my data into smaller grids. Anybody have any suggested workarounds?

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