We’ve finished mapping all 1,309 townships in Ohio! Despite its importance in wayfinding, this quirk of Buckeye State geography has long eluded us, largely due to the townships’ complex relationship to other jurisdictional boundaries:
This was a long project, dating back to Hamilton County’s townships in 2012. We considered a bulk import at one point but had to pump the brakes. No external dataset seemed to hit the sweet spot of freshness, geometric accuracy, and topological accuracy. So we did it the old fashioned way, by hand. It was painstaking work, easy to get distracted from. We had to combine the best parts of the U.S. Census Bureau’s BAS and TIGER products, ODOT’s TIMS, old USGS topographical maps, county GIS layers, legal boundary descriptions, and of course aerial and street-level imagery. By last summer, a dozen years on, we had only completed about half the state.
In the past year, we made a big push to get it done. Thanks to @j0hn33y, @DrDisaster, @Hayleox, @Jared.campbell, @eric22, and others for getting us to completion. Especially @j0hn33y for taking us the final stretch. Now you can see our complete coverage of admin_level=7 border_type=township boundaries in Overpass turbo and Ultra:
But have we really finished? Of course not! We still need someone to verify that we haven’t left any actual holes that are covered by neither a township (at level 7) nor a municipality (at level 8). Municipal boundaries are constantly annexing and detaching territory. In Ohio, this also means township boundaries are constantly changing too, but not necessarily in sync. In QA’ing the boundaries over the past week, I found that maybe a quarter of the municipal boundaries are outdated in ways large and small.
Even when we have an up-to-date boundary, it’s usually quite crude. The TIGER 2008 boundaries we originally imported were quite a work of art, even compared to the imperfect state of TIGER today:
If you’d like to help us clean up these boundaries, go to any city or village in the state and compare the corporation limits to the available imagery. To locate outdated portions of a boundary, you can enable this TIGER layer as a custom background in iD or JOSM. It fills city and village limits and CDP boundaries in a few different colors and delineates township limits in a thin black line:
https://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/Places_CouSub_ConCity_SubMCD/MapServer/export?dpi=96&transparent=false&format=png32&layers=1&bbox={bbox}&bboxSR={proj}&imageSR=102100&size={width},{height}&f=image
TIGER is pretty good for depicting where the municipality has or hasn’t withdrawn from the township, leaving a gap in the township layer, but it can still be quite poor in terms of geometric accuracy in some places. It also has a tendency to snap to linear features, even when there should be a slight offset. Always double-check the lines against other sources before getting too far redrawing a boundary. The USGS Topographic Maps layer tends to have better positional accuracy, but it’s decades old, so only use it when you’re sure the wiggly line you’re seeing in TIGER is supposed to depict an older line that’s in the topo map.
Best of all, look up the history of one of the nodes and see if anyone has edited it recently. A recent edit might indicate that someone has already looked into it and the discrepancy from TIGER is intentional.
Apart from cleanup, we also decided long ago not to map paper townships, because they don’t manifest on the ground by name. But their names are used for some purposes, so it would be helpful to stick them somewhere that a search engine could find them. That can certainly be alt_name=* if the paper township covers the entire municipality, but not if it only covers part of it. Maybe we should map them after all, so that all the state is covered by level 7 boundaries? But how to tag them so no one confuses them for the townships that actually matter?
I’d be remiss if I didn’t share some quirks I learned while QA’ing the township boundaries over the past week:
- The U.S. Board on Geographic Names, which standardizes names for federal use, calls Centerville “Thurman” because there’s another incorporated Centerville elsewhere in the state.[1] The post office is called Thurman, since it’s a federal facility, but otherwise the village is known as Centerville.
- The BGN also renamed Matamoras to “New Matamoras” to avoid confusion with Metamora. But they apparently didn’t find Valleyview versus Valley View too confusing. Go figure.
- I had forgotten that a municipality’s corporation limits can be discontiguous, as in the case of Delphos and its reservoir and Dayton and its airport.
- Some municipalities have turned strip annexation into a sport. South Lebanon has annexed a bike trail but nothing around it, while Canton has annexed a railroad all the way to the county line. Still nothing compared to what Oklahoma’s towns engage in though.
- Typically, a municipality will withdraw from the township it started out in; once it annexes into another township, it might withdraw from that township or have the original township annex part of the other township. But in some cases, the municipality stays in the original township and withdraws from the second or third township. For example, Celina is still mostly in Jefferson Township, but they’ve created a tiny Wayne Township on paper to exclude themselves from Center Township to the north.
- The Ohio Secretary of State’s Office recognizes only 1,308 townships. The 1,309th is Montgomery County’s Wayne Township. Most of the township got annexed away by Huber Heights, but a tiny rump remains on a federal airbase. Without residents, it’s in a state of limbo: unable to fulfill the qualifications for township government, but also unable to dissolve itself.
Many of these oddities point in the direction of splitting corporation limits and jurisdictional subdivisions into separate hierarchies, but for now, at least we can celebrate the (sort of) end of a long journey.
In Montgomery County’s Washington Township and Greene County’s Sugarcreek Township ↩︎
