Reassigning Stray Precincts
When a map is not contiguous or some precincts are still not assigned to districts, sometimes it’s because there are “stray” precincts — individual precincts for one district that are fully embedded within another district or single unassigned precincts embedded within a district.
This can be common in big states — like Texas and California — where the size of individual precinct shapes gets fairly small. In these cases, it’s easy to miss that a precinct either isn’t assigned to any district or is assigned to different district than all the precincts that surround it.
You can find and fix these one at a time, using the “Find Unassigned Precincts” and “[Find] Non-contiguous Districts” features. (See “Finishing Maps.”) However, you can also check for stray precincts and automatically reassign them en masse to the districts they are embedded within, using the “Reassign Stray Precincts” feature.¹
If the tool finds and reassigns any stray precincts, it reports how many.
If no stray precincts were embedded with other districts, the tool reports that instead.
If a map still has contiguity issues or unassigned precincts after running “Reassign Stray Precincts,” you can find and fix them with the “Find Unassigned Precincts” and “[Find] Non-contiguous Districts” tools noted above.
Footnotes
- The tool doesn’t automatically reassign individual precincts that are on the border between two districts or clusters of precincts, because it’s ambiguous what to do in these cases. For the careful reader, sometimes there can also be a lone precinct on the edge of a district and state: This is a stray too — in the sense that it is surrounded by precincts from another district — but because it’s not a hole in the district shape, just an indentation, the technical approach we use doesn’t find these.
