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Summary Some objects, such as cities, are tagged with both place=* and boundary=administrative+admin_level=*. Should it be one or the other, and if so, which one, or is there a conceivable benefit for having both sets of tags? Detailed problem description This is a Nominatim related question. I don't think I will ever run out of those. Here's the outline polygon for my favorite city: http://www.openstreetmap.org/browse/way/33261354 It's tagged with every possible key and it may be a case of TMI (too much information): boundary = administrative plus a full complement of is_in tags (which may or may not be needed depending on who you ask) and the usual tiger: schema tags. I don't know if place_name and border_type tags are of any consequence. However, I believe that because it is tagged as both a place=city and boundary=administrative + admin_level=8, Nominatim ends up importing it twice as two separate places, and it bothers me. Check it out: Irvine as admin boundary polygon Both point to the same OSM polygon. I assume Nominatim has its reason for importing OSM places and admin boundaries separately. I am guessing it does not expect the same object to be tagged as both. What ends up happening, if you look at the children, is that, as far as Nominatim is concerned, one "Irvine" is a parent of the zip codes, most neighborhoods, streets, parks, etc., while the "other Irvine" is a parent of small, but not insignificant number of neighborhoods, shopping plazas, streets, etc. In practical terms, when Nominatim returns a search result set or does reverse geocoding, it is going to list any street or park as being in "Irvine". Whether its one "Irvine" or the "other Irvine" is not that important to the end user, but you have to agree that the situation is pretty clumsy and is rife with potential for data integrity problems (in Nominatim, that is). The fact that there is also a "third Irvine" represented by a node tagged with place=city, with its own subset of children that are missing from either of the other two Irvines, is a whole other story. |
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Check out the "As Areas" section in the wiki page for place. One suggestion there is to mark a node as the "centre" of the city (where the name will go) with place=city. Create a boundary=administrative relation for the perimeter (with the appropriate admin level), and make the node a member of the relation with role=admin_centre. See also the Relation:boundary page. Yeah, I have seen those. The "As areas" best practice is actually a pretty poor piece of advice written without any thought of what having a place node and an admin boundary for the same city, county, etc. object will do to Nominatim searches. I have researched and talked about this issue extensively over the past two days. The consensus today is to delete the place node when a polygon is available, not add one. Adding a node to a relation with a "label" role is a swell idea, but it is not currently supported by renderers.
(14 Apr '11, 03:39)
ponzu
Adding a node to a relation with a "label" role is a swell idea, but it is not currently supported by renderers. True, but doesn't that mean the correct course would be 'add nodes with no tags but with role=label', and lean on render developers to support that? Particularly since "delete the place node when a polygon is available, not add one" seems to be the best/accepted practice, and in that case, most renderers show nothing at all on a map for a border relation without a place node -- right?
(30 May '14, 22:03)
Skybunny
Note that this is a pretty old discussion. One of the Nominatim maintainers recently wrote (here? talk@?) that it is not a good idea to remove the place node if there is a boundary.
(31 May '14, 04:42)
cartinus
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Hey, this sounds quite similar to my recent question: http://help.openstreetmap.org/questions/4068/when-does-it-make-sense-to-use-place-on-an-area Good that there's some more discussion on where the
placetag is appropriate.Similar, yet different. You ask when to use one set of tags vs. the other. I ask if it;s ever a good idea to use both. I am slowly arriving at a conclusion that there isn't, albeit without any input from the gurus.
Why didn't you guys tell me that my links don't work (because of the escaped underscore?) Let me update them and see if the question gets an actual answer.