[Tagging] My "weirdly unnatural aversion to relations"

Mark Wagner mark+osm at carnildo.com
Tue Oct 2 18:17:03 UTC 2018

On Tue, 2 Oct 2018 17:01:33 +0100
Paul Allen <pla16021 at gmail.com> wrote:

> Even if a multipolygon can have many disconnected outers, it seems
> I'd have to make each university
> building an outer.  And then there are no inners.  So even if it can
> be done that way, it seems like
> an abuse of the concept, which I thought was to be able to punch
> exclusionary holes in areas.

"Many outers, few if any inners" is a *very* common way to map
complicated geometry.  A quick look at my local area shows a half-dozen
parks, a campground, a school, and a military base, as well as a town
that would be such a multipolygon if the "boundary" type didn't exist.

Punching holes in an area is a common use of multipolygons, because it
can't be done any other way, but it's hardly the only use.

(It's also very common outside of OSM.  My county's land-ownership
database has thousands of these, where a parcel is split by the
right-of-way for a public road.)


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