On Thu, 3 Sep 2015 18:51:50 -0500 Toby Murray <[email protected]> wrote:
> The area you linked to has no boundary data in OSM. You don't state > this in your email but by pulling up the TIGER shapefile, it looks > like you are wanting school district boundaries? I see one runs > through the area you linked to, in the shapefile. School districts > were not imported into OSM. The only things that were imported from > TIGER is roads, state, county and city boundaries. Interesting. There are lots of linear features that are not roads or the boundaries mentioned. The water feature I described is one. And, yes, I am looking at school district boundaries right now. But really, the question is about any other set of relations that are supposed to tile the map. For example, I knew about Sunnyvale's relation, which you mention below, but there are over 350 cities in California and there do not seem to be that many relations, or I cannot find them (despite some banging of my head against OverPass), or both. I was hoping that city boundaries would follow conventions like "admin_level"="8", "place"="city" and so on. More fool I. Most of these "rules" definitely seem to be honored in the breach. > Administrative boundaries in OSM have always been a tricky subject. > OSM thrives on information that can be verified by someone standing on > the ground, looking around and seeing something that can be put into > the map. Administrative boundaries are (usually) not that way. They > are imaginary lines drawn on the map. Sometimes they follow physical > features but often they don't. So the only source to verify or update > them is to go back to the imaginary line drawer and ask for an update. I had not heard this perspective. I am not sure what to say, other than that though it is a "tricky" subject, it is not really something that can be ignored. Too many things in real life depend on these boundaries. > Because of this, I think boundaries in OSM tend to deteriorate in > quality quicker than other features. Sometimes people modify a way > that is part of a boundary relation and don't realize that they are > affecting the boundary. I have done a lot of work fixing up boundaries > (mostly county) across the country and there are definitely a million > ways to break them. It has occurred to me that there will probably need to be a "boundary watcher" tool, which can let an interested group know about it when a boundary gets broken in some way. And I have started playing with the python libraries for accessing OSM data with this in mind. > > If you want an example of an admin boundary in OSM, here is the > Sunnyvale city boundary relation: > https://www.openstreetmap.org/relation/112145 > Yep. Knew about that one. Here is the table I am keeping my "meta-data" list of relations that I am interested in: mysql> select * from osm_relations; +----+----------------------------------------------+--------------------------------------+-----------------+ | pk | url | name | place | +----+----------------------------------------------+--------------------------------------+-----------------+ | 1 | http://www.openstreetmap.org/relation/112145 | Sunnyvale, CA, USA | city | | 2 | http://www.openstreetmap.org/relation/148838 | United States of America | country | | 3 | NULL | Sunnyvale Elementary School District | school district | +----+----------------------------------------------+--------------------------------------+-----------------+ As you can see, the relation for the SESD still needs to be defined. And there are some others.... TBD. - ray > Toby > > > On Thu, Sep 3, 2015 at 5:40 PM, Ray Kiddy <[email protected]> wrote: > > > > Hello - > > > > I am on a quest to learn more about how administrative boundaries > > can be managed as relations. I have a bit of experience with these > > things, but I am discovering the limitations of my knowledge also. > > Which was the point, actually. > > > > I would like to be able to suggest that governmental entities could > > manage their district geo data with OSM. I am interested in seeing > > why this does not work now and what can be done. Well, and it would > > be interesting to find out why so few cities in California actually > > seem to have a relation. Or perhaps I am missing it. > > > > I know that TIGER data was imported into OSM, but I am seeing some > > disconnects. To be precise: > > > > Using QGIS, I can load the vector files (SHP) from the following as > > two different layers: > > > > ftp://ftp2.census.gov/geo/tiger/TIGER2015/ELSD/tl_2015_06_elsd.zip > > ftp://ftp2.census.gov/geo/tiger/TIGER2015/EDGES/tl_2015_06085_edges.zip > > > > Using JOSM, I can see the "Sunnyvale East Channel": > > > > https://www.openstreetmap.org/#map=19/37.364537971457935/-122.02110206207291 > > > > I cannot see how to get the id of this way from JOSM and its tag > > info seems to be: > > > > boat=no > > intermittent=yes > > name=Sunnyvale East Channel > > scvwd:FACILITY=2026 > > scvwd:ROUTEID=20260 > > waterway=drain > > > > And in QGIS, I can see the same feature (removing empty TIGER > > fields): > > > > wkt_geom LINESTRING > > -122.0213200000000171 37.36408999999999025 > > -122.02097200000001465 37.36464099999999178 > > -122.01992900000000475 37.36629399999999634 > > -122.01963900000001217 37.36675400000000025 > > STATEFP 6 > > COUNTYFP 85 > > TLID 618169892 > > TFIDL 229597201 > > TFIDR 230278901 > > MTFCC P0001 > > HYDROFLG N > > RAILFLG N > > ROADFLG N > > OLFFLG N > > EXTTYP N > > GCSEFLG N > > OFFSETL N > > OFFSETR N > > TNIDF 39083667 > > TNIDT 409312163 > > > > But there seems to be no connection between the feature in OSM and > > the TIGER data. So, TIGER data was used to define new features? But > > perhaps TIGER id data was not merged onto existing features? > > > > I am certainly not seeing "tiger:tlid"="618169892" associated with > > this object in OSM anywhere. > > > > So, if I want to give the Sunnyvale District the relation that > > defines its boundaries, I cannot use TIGER data to find those > > lines? Or rather, I must use the TIGER data and find the line in > > OSM and set up the connection myself? > > > > Ok.... Any other suggestions? > > > > thanx - ray > > > > > > ps: > > > > My early stumblings are in my diary: > > > > http://www.openstreetmap.org/user/rayKiddy/diary > > > > Please excuse any ignorance on my part. I know a bit about the GIS > > practices of the state of California. I have a very small bit of > > experience with Santa Clara County. I have a smidgen of knowledge > > about the city of Sunnyvale. And I have more exposure to the > > Sunnyvale Elementary School District, having once been on the > > Board. And I develop database software and am interested in mapping > > applications. > > _______________________________________________ Talk-us mailing list [email protected] https://lists.openstreetmap.org/listinfo/talk-us
