[landcover] Incorrect labelling of multipolygon relation #4099
Comments
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Author: Ldp These relations seem to have been deleted, so this particular manifestation of this issue is now gone. This is actually an issue that has its roots in the import process, not in mapnik itself. Multiple disjunct outer ways in multipolygon relations each get converted into their own postgis polygon in the rendering database. When mapnik gets around to seeing the data to be rendered, it has no way of knowing that they were once part of a single entity (the relation). So far so good, but where things turn sour is that if the relation itself doesn't have a name tag, it takes a name tag from any one of the member ways. Same for any other relevant tag. The solution is twofold: 1) Explicitly tag the relation with the relevant tags and 2) (the most important) don't use relations to group things together. Relations are not categories. "All residential areas in a particular municipality" is the perfect example. When a proper admin boundary exists, it's easy to answer the question "give me all residential areas in this region". It doesn't need a relation to get that done. |
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Author: rasmusv I think that the original reporters problems have been resolved in OSM, however I've observed something similar in Denmark. |
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Author: math1985 Is this still a problem? |
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Author: math1985 This issue is now being discussed on Github: gravitystorm/openstreetmap-carto#779 Therefore, I will close the issue here. |
Reporter: david[at]frankieandshadow.com
[Submitted to the original trac issue database at 4.28pm, Monday, 21st November 2011]
Someone seems to be rather over-enthusiastically grouping together all the residential areas in Cambridge into multipolygon relations. I'm not convinced this is helpful. However, there is a rendering artefact which makes this particularly unpleasant. The name of one of (the many) outer elements is being picked up and rendered widely across the whole of the area which the relation covers (possibly it is in the middle of any anonymous outers which are also part of the relation, not sure).
The name chosen seems to be pretty random. It comes from this small way, "The Orangery".
http://www.openstreetmap.org/browse/way/43491617
You can then see this insignificant "The Orangery" caption rendered repeatedly all over Cambridge where it is completely irrelevant. For example:
http://www.openstreetmap.org/?lat=52.197111&lon=0.103013&zoom=18&layers=M
and
http://www.openstreetmap.org/?lat=52.190617&lon=0.129325&zoom=18&layers=M
It doesn't seem right to render the name of one element of a multipolygon relation arbitrarily on others.
I think the relation concerned is this one:
http://www.openstreetmap.org/browse/relation/1823059
but it could be this one, I'm not certain:
http://www.openstreetmap.org/browse/relation/1825599
I will contact the author directly about the undesirability of this relation in principle, but I think the way the name is being rendered is a bug in any case.
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