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.