[Talk-us] Proposed import cleanup: NYSDEClands

[Eric Ladner]

On Mon, Jun 20, 2016 at 8:08 PM Kevin Kenny <kevin.b.kenny+osm at gmail.com>
wrote:

> The only way that I can see the current tagging working is if there
> is some hidden coupling where it is understood that tags that apply
> to an outer way of a multipolygon relation actually belong to the relation
> itself, and the inner ways are excluded implicitly. If so, that puzzles me,
> because that's also not what I see the renderer assuming.
>
> Can someone please explain to me how I should be tagging things
> so that the polygon-with-a-hole becomes a protected area? The ones I did
> in the Catskills, like https://www.openstreetmap.org/relation/6304902
> appear to render as I intended, but I know that there is lots of nonsense
> tagging that still renders prettily.
>
> Kevin
>

I think your perception of how multi-polygons work is correct.  Tagging
should be at the multipolygon level.  E.g. if it's a  park split by a road
maybe, both ways are members of the multipolygon, and the relation is
tagged with "type=multipolygon; leisure=park" and both ways with
"role=outer".  Maybe if there was something in the middle of the park, it'd
have a ring, that was tagged with nothing, but has "role=inner" on the
relation.  But, if it was a substation or lake or something, you could tag
the inner ring with natural=water or power=substation.

Granted, if you tagged the outer ways directly and left the relation with
nothing but "type=multipolygon" it would still render correctly, but it's
not the correct way to convey information.   Just because it looks pretty
on the map doesn't mean it's right.

JOSM flags this condition (tagging on outer ways instead of the MP itself)
as a warning when you're uploading.  That's probably a good indication it's
not a good practice.

Think of it from a data maintenance point of view.  If you have some huge
national park with 30 outer rings, do you want to manage 30 separate sets
of information on each outer way, or one set of information on the
multipolygon relation they all belong to anyway?

Eric
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