Hi Marko, thanks for the explanation. So I'll better use other data for testing ;-) Gerd
Date: Sun, 12 Jan 2014 23:55:20 +0200 From: marko.makela@iki.fi To: mkgmap-dev@lists.mkgmap.org.uk Subject: Re: [mkgmap-dev] Question regarding duplicated shapes
On Sun, Jan 12, 2014 at 03:46:30PM +0100, Gerd Petermann wrote:
while debugging the shape merger I found many duplicated shapes in Finland, and I am not sure how mkgmap should handle them.
Oh, the Corine import by "teollisuus" ("industry" in Finnish) is hopeless IMO. :( It is based on very inaccurate data, and the converter is generating duplicate ways and improperly tagged multipolygon relations, like in your example.
Instead of defining the area-style tags on the multipolygon relation itself, this import added the tags to all relation members (both role=inner and role=outer). JOSM at least used to display this as intended, IIRC.
Whenever I have fixed some multipolygon error in Finland, I have tried to remove the duplicate shapes, and to move the area-style tags to the multipolygon relation. It is sometimes tricky if someone has already tried to edit the imported data.
Example:
http://www.openstreetmap.org/way/105723026
is tagged landuse=farm and is the role=inner member of multipolygon relation http://www.openstreetmap.org/relation/1504949 which has only one role=outer way which also is tagged landuse=farm. Way http://www.openstreetmap.org/way/105719041 is a copy of way 105723026, but with reverse order of points. It is tagged natural=scrub
Yes, this is exactly what I have seen many times.
FWIW, I do not think that mkgmap should spend too much effort in supporting this broken and redundant way of mapping multipolygons. The Corine data is very low-resolution, basically useless. Now that we finally got the license stuff sorted out at http://www.openstreetmap.org/copyright the import from the National Land Survey database is "only" a matter of writing and configuring a converter, and manually resolving conflicts with existing data. In this process, the Corine landuse imports will probably be deleted.
Best regards,
Marko _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev