[OSM-talk] Best way to draw areas with holes?

[Dave Stubbs]

On 20/12/2007, Rahkonen Jukka <Jukka.Rahkonen at mmmtike.fi> wrote:
>
>
> Hi,
>
> Some area features would be drawn in GIS world as polygons with holes but
> that is not well supported by OSM data model.  I mean, for example, landuse
> which has islands with some other landuse or big buildings having inner
> courts or patios.  I have seen that users have solved this in many
> innovative ways but most of them seem to lead to more or less odd rendering
> at least in case of buildings.  Is there any recommended way to draw and tag
> this kind of objects?  To draw an area in the halves, or delineate a
> building as a fat loop sharing some points at a seem (non-existing in real
> world) to make it look like a closed area, or what?
>

Use the multipolygon relation.
It'll be rendered by the Mapnik layer at least.
http://wiki.openstreetmap.org/index.php/Relations/Multipolygon

Unfortunately you can't do that in Potlatch yet, so you'll need to be
using JOSM or some other editor which supports relations.