[OSM-dev] Tagging of multipolygons with holes within holes
Frederik Ramm
frederik at remote.org
Wed Oct 17 12:05:34 BST 2012
Hi,
On 10/17/12 12:58, Martin Koppenhoefer wrote:
> 2012/10/17 Igor Brejc <igor.brejc at gmail.com>:
>> Another thing that's odd is the duality of inner rings: they represent
>> holes, but they can also represent holes AND separate polygons at the same
>> time. Decision on which is which has to be made based on a vague notion of
>> "difference" in tagging.
>
> This is something I don't find odd. An inner ring is always a "hole"
> in the multipolygon, but it is clear that what is inside this ring is
> not "nothing" but something, and this something will often also be
> tagged. But it is tagged on the ring itself (or on a different
> multipolygon where it is an outer way), so I don't see where the
> "decision" comes into play. Or are there implementations where the
> tags of inner ways get also inherited to the multipolygon-area?
Igor probably refers to the situation where you have a multipolygon with
an outer and inner ring, and both rings are tagged landuse=forest. In
that particular tagging, which is supported by most applications as a
form of backwards compatibility, the hole is *not* a forest ;)
Bye
Frederik
--
Frederik Ramm ## eMail frederik at remote.org ## N49°00'09" E008°23'33"
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