I currently have shapefile of US PUMAS and another feature shapefile (call it feature X). I am using ArcPy to project both of these files to the following projection coordinate system (using Project_management):


After projecting, I use intersect_analysis and then CalculateAreas_stat to compute the intersection areas. Finally I output a .csv file, which I then use to compute area weighted means.

The issue is that every time I run my simple script, the intersection areas vary by a small amount (somewhere to the 8th decimal point). These small changes are impacting my analysis.

If this is a GIS precision issue or if I making a mistake, how can I go about fixing it?

closed as off-topic by PolyGeo Oct 7 '18 at 3:25

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  • I suggest loading the shapefiles into a file geodatabase, don't work with the shapefiles which have lower precision. Another thing - why do you use the CalculateAreas_stat, any specific reason for that? I suggest using the Calculate Field with the !shape.area! resources.arcgis.com/en/help/main/10.2/index.html#//…. – Alex Tereshenkov Mar 10 '15 at 11:39
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    Shapefiles have lower precision? That's not correct. Shapefiles and (high precision) geodatabases are both using the equivalent of double precision. – mkennedy Mar 10 '15 at 15:48