[OSM-dev] Relation member_roles from Osmosis import

Peter Budny peterb at gatech.edu
Thu Oct 28 15:18:26 BST 2010


Frank Broniewski <brfr at metrico.lu> writes:

> Hello Jochen,
>
> thanks for your answer, that makes it clear. I have another question
> about relations.
>
> I found a relation, a lake in Germany,  (id=1104680, Schweriner See
> (Außensee)), which has serveral inner relations to ways. Some of these
> ways form a closed ways, so it's easy to create a polygon from it. But
> other ways with the relation role "inner" are not closed, but they
> form together an island in the lake.
>
> Should't those form a relation of themselves before relating them to
> the lake relation with an inner relation? The ways I am speaking of
> are
>
> 24563810
> 70191810
> 70191809
> 70191807
>
> Luckily those ways form an island but if there would be another island
> formed by ways without relating them together it is quite difficult to
> recreate them properly. Is this situation an exception or is this a
> common situation?

I don't know if it's common, but it is documented on the wiki as a valid
way of using multipolygons.

It may not be the best way, though.  If the islands have any tags
associated with them (like name=*) it would probably be better to split
them off into their own relation.
-- 
Peter Budny  \
Georgia Tech  \
CS PhD student \



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