Hi David,
Apologies for the late response; I don't read the imports list often. As
an active mapper in Southwest Ohio, I thank you for your interest in
improving this part of the map.
On 09:50 2014-02-25, David Days wrote:
Greetings, all.
I am a new user to OpenStreetMap, but a long-time software developer.
Currently, I'm working on a project that would benefit from having
political subdivisions in the state of Ohio represented on a map. A
quick run through of the import history page doesn't show any similar
data sets, so it appears that the results could be a worthwhile
contribution.
The TIGER import left a ton of correct-only-if-you-zoom-out boundaries
for counties, cities, and villages, but inexplicably omitted township
boundaries. I've been manually entering township lines and correcting
existing TIGER county and city/village lines off and on for the past
year or so, but it's a neverending task and an import would be much more
efficient. To my knowledge, there haven't been any imports specific to Ohio.
To clarify, "political subdivisions" means not only the standard mapping
features (city, village, county), but also township, voting wards and
precincts, congressional districts, etc. Some of these divisions are
atomic (don't cross other jurisdictional lines), while others can cross
several larger groups.
OSM needs Ohio township boundaries. They're stable and much more real
than the CDP boundaries that came with the TIGER import. However, I
would draw the line at structures that lack any governing body. (CDP
boundaries never should've been imported.) Voting districts are better
suited for external databases that can be "mashed up" with OSM,
especially since, at least in theory, a county board of elections can
completely redraw its precincts for each election.
The intent is to start with one county at first, then expand as the
project grows. That translates into roughly 100 subdivisions, of which
75+ are non-city/town/village in the first data set.
I'm planning on getting local experts within the areas described to
manually create the mapping features at first, but eventually I would
like to take other public domain data that's coming available and import
it on a large scale.
(As for licensing and reuse--the political divisions themselves are
public domain, and I'm the owner of the project; even though the primary
purpose is narrow, I thought that OSM and everyone else could benefit
from having this map available).
Where does this data come from? Would it be feasible to start out by
publishing a tile server that mappers could manually trace atop? That
way, we can accurately align boundaries to real-world features (roads,
creeks, edges of farms, etc.) when it makes sense to.
With all of that in mind:
1. Good idea, ok, or really, really bad idea?
2. Reuse of existing datapoints is probably important (these divisions
usually follow clear boundaries, so finding existing boundary or
markers would cut down on the import size). Pointers or gotchas?
Out-of-state mappers are often confused by the relationship between
cities/villages, townships, and counties in Ohio. Cities and villages
can span multiple townships and multiple counties. Some cities and
villages have "withdrawn" from their townships, leaving a hole at
admin_level=7. Some cities are no longer fully withdrawn: recently
annexed land may still be part of a township. It's hard to get these
details right without careful research or some contacts on the ground.
You'll find that the county lines (from the USGS), city/village lines
(from the Census Bureau), and CDP lines (from someone with a vivid
imagination at the Census Bureau) often disagree. If your data set turns
out to be more accurate, perhaps we should try to align existing
boundaries to your data in a manual import.
3. Import scale: Ohio has 88 counties, with probably 100 of these
subdivisions on average. If the entire idea is acceptable, would
per-county imports work better for the community, or would it be
better to get it all together and push it all at once?
I would suggest starting by reaching out to active mappers in the metro
areas, to see if anyone would be interested in helping out with a manual
or closely-supervised import in their immediate area.
Unfortunately, not every part of the state has an active community to
speak of. You might be able to enlist some mappers from the big metro
areas to help out with Southeast Ohio, for instance, but there isn't a
whole lot for an armchair mapper to go off in those hilly areas.
4. Maintenance: Most of these areas are pretty stable--about 100 out
of the whole state get reworked every 10 years. Is this a factor,
and how much commitment to maintenance should I factor in?
If I recall correctly, annexation laws got stricter several years back,
so city and village boundaries are mostly stable, even among the suburbs.
--
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