[Tagging] Another multipolygon question

Joseph Eisenberg joseph.eisenberg at gmail.com
Mon Oct 29 02:23:04 UTC 2018

You can make any number of relation members with role “inner”. So if the
refuge has outlying areas which have a hole in them, the way(s) around the
outside are role=outer and the way(s) around the hole are role=inner.

It really is “multipolygon”: as many polygons as you want, with as many
holes and donut shapes as you need.

On Mon, Oct 29, 2018 at 9:12 AM Dave Swarthout <daveswarthout at gmail.com>

> Okay, next question.
> I added the Laguna Atascosa National Wildlife Refuge to OSM yesterday . (I
> don't do much mapping in Texas but that place is special because I once did
> a water quality assessment there as a volunteer.) It's a fairly large
> multipolygon and the main relation holds the bulk of the refuge territory.
> However, there are scattered about several other areas, some of which are
> also multipolygons, that are part of the refuge.
> Simple areas can be easily included as "outers" in the main relation (Rel
> ID:885828). But what about other pieces that are multipolygons? I could
> simply add them as separate relations with identical tags but handling such
> areas that are connected administratively but not physically would seem to
> be one reason multipolygons were invented. But I'm thinking there must be a
> more elegant method. And what about inner areas that are also
> multipolygons? This case cannot be handled by my simplistic approach.
> How should I deal with this?
> Thanks in advance,
> Dave
> On Fri, Oct 26, 2018 at 10:07 PM Kevin Kenny <kevin.b.kenny at gmail.com>
> wrote:
>> 26. Oct 2018 11:52 by daveswarthout at gmail.com:
>>> Thanks, That helps a lot. I don't work with routes (yet) but it when I'm
>>> adding inners to riverbank multipolygons I always add them in the order
>>> they would appear if you were traveling downstream. It just makes sense to
>>> me although there's probably no programmatic reason to do it.
>>> On Fri, Oct 26, 2018 at 5:55 AM Mateusz Konieczny <
>> matkoniecz at tutanota.com> wrote:
>> > Order of elements is saved in OSM database.
>> That appears to be the answer to a different question.
>> The 'sort' operation in the JOSM relation editor changes the order of the
>> elements. If the layer is uploaded, the new order of elements, as produced
>> by the 'sort' operation, will replace the old order in the OSM database.
>> This is usually what I want with a multipolygon. With a route, I find
>> myself undoing or further altering a 'sort' operation much more often,
>> because there are often things about routes that JOSM doesn't get quite
>> right. (Example - a dual carriageway where both ways end in link elements
>> looks as if the route has floating endpoints, and the sort operation messes
>> up one of the directions.) Even there, though, the 'sort' is usually Pretty
>> Close to right, and is often usable as a starting point. Moreover, I'm not
>> sure that it can be improved. The topology of a route isn't always quite
>> right in the field, and some of 'getting it better' amount to 'read the
>> mapper's mind,' something computers are ordinarily not well equipped to do.
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> --
> Dave Swarthout
> Homer, Alaska
> Chiang Mai, Thailand
> Travel Blog at http://dswarthout.blogspot.com
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