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

Frederik Ramm frederik at remote.org
Wed Oct 17 08:40:34 BST 2012


Hi,

On 10/17/12 08:15, Igor Brejc wrote:
> But the problem is in how to handle tagging in this case. The existing
> wiki "rules" describe only the tagging of top outer rings, but they
> don't mention how to handle various cases/combinations of tagging holes
> within holes.

The area of the "hole within the hole" does not require special tagging, 
as it is covered by the multipolygon itself. If you have a forest with a 
hole in a hole, then that hole in a hole is forest as well.

If you are, on the other hand, thinking of a "lake in the middle of a 
meadow in the middle of a forest" situation, then this is not "hole in a 
hole" - the forest has one hole which is the meadow, and the meadow has 
one hole which is the lake. You would have three ways:

F - tagged as forest
M - tagged as meadow
L - tagged as lake

and two multipolygons

MP1: outer=F, inner=M
MP2: outer=M, inner=L

You have the option of leaving F and M untagged and attaching the 
forest/meadow tags to MP1 and MP2 instead.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"



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