[OSM-talk] multipolygon (lake) not rendering
frederik at remote.org
Mon Oct 26 09:24:42 GMT 2009
Rahkonen Jukka wrote:
> I meant "Do all the polygon parts get their correct names in
There are multiple renderers and they generally don't agree on how to
I would assume that most can deal with a hole of a multipolygon having
its own identity (e.g. hole in forest tagged as farm).
Most will probably not be able to derive the identity of something from
the kind of polygon surrounding it - i.e. you will probably have to tag
an island as such, and not count on the renderer knowing that everything
that is a hole in a water polygon will automatically be an island.
There is also a problem with touching holes; if you have a forest and in
the forest there is a farm and a lake next to each other, then some
people draw a forest with two holes, whereas standard simple feature
geometry does not allow touching holes (and anyway, as you correctly
say, for export e.g. in shapefiles, extra polygons would have to be
created for the holes).
A further problem arises when the hole boundary consists of multiple
ways, something that is allowed for advanced multipolygons, but you
would not be able to place the name of the island (or whatever) in this
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