[Tagging] What is and what isn't a valid type=multipolygon relation for osm ?

Martin Koppenhoefer dieterdreist at gmail.com
Sat Oct 13 18:02:51 GMT 2012

2012/10/13 David ``Smith'' <vidthekid at gmail.com>:
> I think the mappers who might break a multipolygon's validity probably don't
> have the patience to read through several rules written in math-speak.

from my experience many are not even aware that there was a
multipolygon involved in their edit when they break them.
I think there are already a lot of pictures on these pages, and some
of the "rules" added are recommendations or already inherent in other


* "Member ways MUST have two or more nodes" --- all ways must have 2
or more nodes

* "Exactly two unclosed ways belonging to a role, and no more should
share an endpoint (eg. the most extreme nodes of a way represented by
the black dot in the images). If an endpoint is shared by less than
two unclosed ways, the polygon can't be closed and is ill formed.
invalid example 1
If an endpoint is shared by more than two unclosed ways, it's ill
formed and a closed polygon can't be reconstructed unambiguously.
invalid example 2"

this is saying that you can't have 2 touching inner rings with a
shared inner way, but you can according to previous docs.


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