[Talk-us-massachusetts] help forum isn't

[Brian M. Sperlongano]

On Mon, Jul 18, 2022 at 11:43 AM <hobbit at techno-fandom.org> wrote:

> https://wiki.openstreetmap.org/wiki/Multipolygon_Examples  strongly
> implies
> that inner-role *relations* are perfectly okay.  And iD doesn't try to stop
> me from assigning one.
>

I think you are misreading that article.  You can have an outer inside of
an inner (concentric rings, for example), but a relation as a member of a
multipolygon would not be recognized by any data consumer I'm aware of as
part of a multipolygon.  A relation is simply a collection of other OSM
primitives (node/way/relation) with an optionally-associated role per
member, and a set of tags for the relation as a whole.  Any editor will
happily allow you to create a complex data structure that doesn't mean
anything to standard data consumers (though hopefully they provide a
warning).

Regarding the question previously posed, the way I generally tag these
types of areas are:

1. land cover (multi)polygons are constructed to cover the actual area of
land covered by the land cover.  In the case of forests (which is the vast
majority of our land cover of course), I try to make separate polygons for
different leaf types (needleaved/broadleaved/mixed), though this depends on
having leaves-down (late fall/winter) imagery to determine this, and it's a
bit of an art.  But data consumers do render this difference so I try to
separate them.
2. I draw TOTALLY SEPARATE boundary relations for the boundaries of
protected areas such as nature reserves.  I tag them as
leisure=nature_reserve or other "similar" protected area tagging such as
boundary=protected_area + protect_class=whatever +
protection_title=whatever.

With this treatment, the land cover renders on the bottom, and the
protected area boundaries render on top as an outline.  This accurately
separates land cover from boundaries.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk-us-massachusetts/attachments/20220718/d575fbf9/attachment.htm>