Sunlight reaches the pale flesh of CAGIS
November 11th, 2014
I was shocked to discover today, thanks to Jskinner at UrbanOhio.com, that the Cininnati Area GIS (CAGIS) seems to have released a large and important subset of their data to the public.
I really am shocked…
Just last year I had a fairly long email exchange with some CAGIS folks, including eventually a City of Cincinnati lawyer, who insisted that the data which they collect with public dollars for civil uses was not a ‘public record’ per Ohio state law. They gave no justification for that claim of course, but I didn’t, as they well knew, have the time or money to take them to court. But anyway…if they want to start playing nice and sharing some of their toys, I’m willing to let bygones be bygones.
So what’s in there? There are two files, the larger of which (‘annual release’) you probably don’t need to bother with. The smaller file (‘quarterly release’) has some real goodies which I’ll describe below. I say that you don’t need to bother with the larger file because it looks like it only has data which could be derived from public domain federal sources like the Census and the USGS. Those sources cover the whole US and are readily available, so why trust CAGIS employees to mediate when you can go straight to the source?
Here’s what’s in the ‘quarterly release’ file(with some notes of my own):
- Building footprints, Hamilton County (they seem to have cut out all of the data on each building and just left us with the outline. Still, for what it is, the data set looks to be very thorough with ~360,000 buildings.)
- Street Centerlines, Hamilton County (I would suggest OpenStreetMap as better for most uses, though there are some other fields in here which I haven’t properly explored. I did notice that the speed limit field seems to indicate a whole lot more 15mph streets than actually exist. The street I live on is tagged as 15mph and physically signed as 25mph for example.)
- Neighborhood Boundaries, Cincinnati
- ‘Sidewalks’, ‘Pavements’, ‘Driveways’ & ‘Parking’, Hamilton County (These are lines only, no data or metadata. They might be useful for CAD-type architectural drawings, but for any sort of spatial analysis they’re probably not worth much.)
- Zoning, Cincinnati and parts of Hamilton County
- Railroad, Hamilton County (You’ll do better getting this from a federal source or from OpenStreetMap)
- Parks, OKI Region (I’m not sure how CVG is considered a park, but this looks like an interesting dataset, with lots of useful fields like name and who’s responsible, and where you can find them)
- Parcels, Hamilton County (There’s tons of juicy stuff in here, like the assessment and sale values for each and every parcel. I played with this a bit in the past, before I knew how to make maps.)
- ‘Subdivisions’, Hamilton County (This looks like a legal artifact more than anything. It seems to contain any parcel that’s been subdivided since GIS was invented. There are many ‘subdivisions’ downtown for example, and I can’t make any sense of other areas that I know well. 1/10: do not use.)
There are a few other datasets in there, but they’re either very obscure (survey benchmarks) or redundant (parcel ‘pages’) to other datasets. As far as I can make out, each of the files is projected in the Ohio Southern State Plane, EPSG 3735, though some of them appear to be missing that metadata.
Again, here’s the link to the data. Go nuts!
IANAREA (I am not a real estate agent) but…
Property developers likely care about the subdivision layer inasmuch as individual homeowners care about the parcel layer. This comes up quite a bit in the suburbs, where farms are still being turned into residential developments. What most folks think of as a “subdivision”¹ usually consists of multiple legal subdivisions corresponding to the farms or homesteads that got bought up. The boundaries may date to when these properties were originally platted.
There’s also an address layer that’s probably better than anything you could get from the Census Bureau (and certainly cheaper than anything you can get from the USPS).
1. With an HOA and a silly name like “The Oaks at Willowcreek Estates”²
2. The oaks and willows both having been felled some years ago.
Why download their data when you can just access their data on the fly by connecting to there GIS database, https://cagisonline.hamilton-co.org/arcgis/rest/