[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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