[mkgmap-dev] Question regarding duplicated shapes

Sun Jan 12 21:55:20 GMT 2014

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