I am working in ArcMap. I have a map of districts in South Carolina, and I'm trying to find the boundary length that every district has with every other district, and the boundary of South Carolina itself. I understand that the GeoProcessing tool Polygon Neighbors can find the boundary lengths between polygons, but I also need the length that a district has with the edge of the state.
I am trying to verify that whatever values I get here correspond accurately with the perimeter of each district, so I don't simply want to use the perimeter tool and subtract off the sum of other neighbor lengths.
I have considered creating a buffer polygon around the state to act as an "outside" district, but I'm not sure how to do that.