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I would like to assess the spatial accuracy of a load of polygon shapefiles which are supposed to show air quality for a bunch of countries. Firstly I want to assess whether each shapefile has a complete coverage of the country it is supposed to represent. Secondly I want to assess whether there are any slithers in the shapefiles, areas which fall out of the country boundary. My initial method is using the rasterize polygon method, using the extract by mask tool to exract the supplied data by a known country boundary shapefile, and perhaps counting the pixels in the original file, and the extracted file, for each case. Can you think of a more efficient method for doing this? I tried to use the split function but it didn't work as I expected it would.

Thanks

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Have you looked at the Symmetrical Difference tool? –  Chad Cooper Feb 20 '12 at 14:20
    
I would convert the shapefile to File Geodatabase with High Precision - help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//… –  Mapperz Feb 20 '12 at 22:23
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up vote 2 down vote accepted

You should be able to identify gaps by using Union with your input polygons and an additional polygon feature class containing one polygon that covers the extent of your data. If you use the NO_GAPS option the gaps will have FID = -1 and blank attributes.

To identify overlaps use Intersect with just the one input dataset. Your thinnest overlaps will be your slivers (it is snakes that slither :-).

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