Working with both ArcGIS and Oracle Spatial, a self-intersecting polygon renders a geometry invalid. Why are self-intersecting polygons a problem?
[GIS] Why are self-intersecting polygons bad
geometryinvalid-data
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If I zoom in here...
I see this:
I think the issue stems from the limitation that a shapefile cannot store arcs. Instead it does a linear approximation. When a polyline intersects (what is intended to be) a circular arc at a tangent the zig zag approximation results in an intersection.
I'd recommend storing the geometry in something that supports circular arcs, like a file geodatabase. There is an open source API available for it. When was Esri File Geodatabase API made available?
Is it feasible to just manually edit the vertices and remove the self intersections?
I do this a lot (using QGIS because it seems to be less picky about this issue). QGIS also has a 'Check Geometry' tool that will show you where all the self intersections are.
I know you said you're running arc but this might be a helpful approach if nothing else is working.
Best Answer
It becomes hard to tell what is the inside and what is the outside of the polygon.