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Legitimate islands will cause "Must Not Have Gaps" false positives. If there are many islands they can add time, complexity, and risk of mistakes to the topology fixing process described here Insert link. These can be avoided by preparing and evaluating a union of the COD-AB and a surrounding 'world' polygon shapefile, which is then removed after any topological errrors errors are fixed. This optional process should be done at the beginning of the COD-AB topology evaluation and is described below.
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- Use the ArcToolbox > Analysis Tools > Overlay > Union tool to combine the shapefile or feature class with a 'world' polygon. For the most universal applications, a 'world' polygon is a shapefile or feature class with one polygon that extends from 90°N to 90°S and 180°E to 180°W, although any polygon completely surrounding the COD boundary polygons will be sufficient. A sample 'world' polygon shapefile is available here. The resulting union will become the 'input shapefile or feature class' described below.
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