[Talk-us] Coastal Maine needs love
Recently, I wanted to fix a few local islands and public parks in coastal Maine, where I have local knowledge. But much to my dismay, the local area was pretty thoroughly broken: - The county lines along the coast are based on a really old (and incorrect) data set. - There's some confusion between towns (admin_level=8) and sub-town boundaries (admin_level=?). - Most towns are marked with nothing more than GNIS points. As a result, the local maps are incorrect, ugly (thanks to the bad county lines everywhere) and incompatible with Nominatim. I've prepared a more detailed explanation of what's wrong, with pictures, examples, and a couple of possible ways to improve things: https://wiki.openstreetmap.org/wiki/User:Ekidd/Coastal_Maine_problems Personally, I'd be interested in tackling 4 small towns and maybe the Lincoln county boundary. But it looks like a large portion of the Maine coast suffers from similar problems. If anybody feels qualified to address the larger problems, I'd be grateful—and happy to help out. Thank you for your feedback and suggestions! -Eric ___ Talk-us mailing list Talk-us@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-us
Re: [Talk-us] Coastal Maine needs love
Thank you for your response! I've made two test edits: - I imported TIGER County Subdivision files for four town boundaries. - I modified an existing TIGER Place outline to be admin_level=9, because it's a actually a subdivision of the real town. That's the brown blob on my example map. I've linked to the changesets here: https://wiki.openstreetmap.org/wiki/User:Ekidd/Coastal_Maine_problems#Experimental_edits Initial results are promising: Nominatim works! And the map looks better. So here's what it would take to make coastal Maine much better: 1. Use modern TIGER County data to replace the existing coastal counties. 2. Consider using TIGER County Subdivision data to give us actual town boundaries, and sort out the confusing mess of GNIS nodes that breaks Nominatim. 3. Decide whether we want to do anything with pre-existing TIGER Place outlines that are smaller than towns. I think (1) is safe, and not too much work at all. Maine only has 8 coastal counties, and they're really broken, so almost anything would be an improvement. (2) would help, but it's definitely more work. (3) is just a matter of deciding; the actual changes would take about 20 seconds for Lincoln county. Anyway, I'm happy to grab the necessary shape files, and use QGIS to simplify them, to convert them to WGS 84, and to break them into lines. But maybe we would want to do something more than that. I'm just a novice. :-) What do people think? Is it worth trying to do something about the Maine coast? 2014-10-15 11:31 GMT-04:00 Martijn van Exel m...@rtijn.org: Hi Eric, Great to see some love for coastal Maine, where I have no local knowledge whatsoever. Do you think there may be a MapRoulette challenge in there perhaps? Or a tasking manager job so we can distribute work? I'd be in favor of replacing county boundaries with something more recent seeing how bad the quality is. Would require conflation and fixing relations at the edges of the work area, I guess, but may be worth it. Martijn On Wed, Oct 15, 2014 at 8:56 AM, Eric Kidd emk.li...@randomhacks.net wrote: Recently, I wanted to fix a few local islands and public parks in coastal Maine, where I have local knowledge. But much to my dismay, the local area was pretty thoroughly broken: - The county lines along the coast are based on a really old (and incorrect) data set. - There's some confusion between towns (admin_level=8) and sub-town boundaries (admin_level=?). - Most towns are marked with nothing more than GNIS points. As a result, the local maps are incorrect, ugly (thanks to the bad county lines everywhere) and incompatible with Nominatim. I've prepared a more detailed explanation of what's wrong, with pictures, examples, and a couple of possible ways to improve things: https://wiki.openstreetmap.org/wiki/User:Ekidd/Coastal_Maine_problems Personally, I'd be interested in tackling 4 small towns and maybe the Lincoln county boundary. But it looks like a large portion of the Maine coast suffers from similar problems. If anybody feels qualified to address the larger problems, I'd be grateful—and happy to help out. Thank you for your feedback and suggestions! -Eric ___ Talk-us mailing list Talk-us@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-us -- Martijn van Exel skype: mvexel ___ Talk-us mailing list Talk-us@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-us
Re: [Talk-us] Coastal Maine needs love
Thank you, everybody, for your advice. Special thanks to Peter for his experience with similar issues in New Hampshire. Earlier today, I added 4 towns on the Boothbay peninsula, which was a nice, low-risk change. Just a moment ago, I updated the southern half of Lincoln county with the TIGER 2014 county data, splicing it into Sagadahoc and Knox counties on either side. This is a pretty big change, and I was as careful as I could be, but I'd appreciate another set of eyes. Wiki: https://wiki.openstreetmap.org/wiki/User:Ekidd/Coastal_Maine_problems County: https://www.openstreetmap.org/changeset/26104709#map=8/44.090/-68.730 Everything was done with boundary lines and relations, and I cleared up all JOSM validation errors on the parts I touched. Overall, this sort of cleanup seems like it would help coastal Maine a lot. The maps are a lot nicer looking, and Nominatim is working now. That only needs 7 counties that are in need of love. :-) (And one which is in need of review.) -Eric 2014-10-15 14:25 GMT-04:00 Peter Dobratz pe...@dobratz.us: On Wed, Oct 15, 2014 at 9:33 AM, Eric Kidd emk.li...@randomhacks.net wrote: Thank you for your response! I've made two test edits: - I imported TIGER County Subdivision files for four town boundaries. - I modified an existing TIGER Place outline to be admin_level=9, because it's a actually a subdivision of the real town. That's the brown blob on my example map. I think you are on the right track with the TIGER County Subdivision files. I did a lot of work on the town boundaries in New Hampshire and it probably had the same sort of mess you are seeing in Maine. Boundaries for towns were imported multiple times by different users and the county boundaries were imported using a much lower precision source. At least in New Hampshire, the county boundaries are most often coincident with town boundaries, so it makes sense to have these in OSM as Relations (not as closed Way polygons) and sharing the Way objects among multiple boundaries. Also, the TIGER CDP shapes were erroneously used in place of the actual town boundaries. The CDP for a town is often generally where the most of the people live, but the actual boundary for the town is a much larger area and this can be verified against town-line signs on the ground. The TIGER boundary data seems to want to share nodes with TIGER road data even though it doesn't actually make sense. For example, town boundaries are often straight lines, but in TIGER these lines are slightly jagged so that they can share points with roads that are close to the town line. If you look at resources like property tax maps that some towns make available, you can see that in many cases the TIGER boundary data should just be made into straight lines. And straight lines in OSM should just be represented by a Way connecting 2 Nodes (your simplify step in QGIS will get you most of the way there). Tagging on the Ways is completely optional as that information should all be in the admin Relations. However, the consensus is that the Ways should have the admin_level be the lowest number (for example admin_level=6 for Ways that make up both a town and a county boundary) rather than trying to have multiple values separated by semicolons. Generally, I have used admin_level=9 for areas inside of towns that appear to be separately administered. In some larger towns, I used admin_level=9 for the wards or districts which correspond to seats on the local government. Towns have also been imported as single nodes, which could be influencing your Nominatim results. These place Nodes should be added to you admin Relations with role admin_centre or label. You should also add wikipedia tags to the boundary relations as this will help Nominatim determine the place hierarchy. --Peter ___ Talk-us mailing list Talk-us@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-us
