[OSM-dev] Tagging of multipolygons with holes within holes

[Martin Koppenhoefer]

2012/10/17 Igor Brejc <igor.brejc at gmail.com>:
> On Wed, Oct 17, 2012 at 1:05 PM, Frederik Ramm <frederik at remote.org> wrote:
>> 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 ;)
>>
>
> Thanks Frederik, that's another one of those "oddities" ;)


+1, this is really odd as well. I think for "forward clarity" it would
be better to render these inner holes as forests as well, so the
mappers will probably remove this tag if it isn't a forest. It just
gets too complicated and weird otherwise. E.g. how would you treat a
multipolygon tagged as landuse=forest with an inner hole tagged itself
as natural=wood? You can't asume in OSM that the same feature will
always have the same tags to describe it.

There could also be reasons (e.g. boundaries, names) why someone cuts
a hole into a forest where also the hole is a forest (with different
properties).

cheers,
Martin