I have come across a few mapping areas which have problems with inner and outer tags, and I am not sure what is considered to be best practice.

So here is a scenario,

Imagine a residential area, within that area is a golf course, on the golf course there are a number bunkers ( sand ) and a few areas of woodland, also a lake and in the middle of the lake is an island which has a wood on it, and a pond and also more sand( bunkers ), I am not sure what the relationships on OSM are meant to be.

Any help or guidance would be appreciated.

Regards

Gary

asked 28 Jul '16, 14:18

Rossendale%20Gary's gravatar image

Rossendale Gary
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accept rate: 20%

edited 28 Jul '16, 14:21


First, "inner" and "outer" are not tags. They are roles of relation members. Each member of a multipolygon relation gets such a role, either "outer" for the ways making up the outer boundary of the area, or "inner" for the inner boundary.

So in your example the outermost area is the residential area. You create a multipolygon relation with the tags type=multipolygon and landuse=residential. The ways making up the boundaries of this area are untagged, but they get the roles "outer" and "inner" in the relation. Then you create another relation tagged type=multipolygon and leisure=golf_course. Its members are the ways you put in the residential area relation as "inner", but this time they are "outer". You add new "inner" ways to this relation for the holes in the golf course. And so on. So all the ways (except outermost and, possibly, innermost boundaries) do double duty as the inner boundary of the outer area and the outer boundary of the area nested inside of it.

Arguably the sand bunkers of a golf course are part of the golf course. They are not in holes in the golf course. So the golf course should probably tagged over all it contains with no inner holes. But the golf course is not part of the residential area, so a hole in the residential area makes sense. It is somewhat unclear what to do in each situation. Use your judgement.

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answered 28 Jul '16, 14:50

Jochen%20Topf's gravatar image

Jochen Topf
4.4k54564
accept rate: 34%

edited 28 Jul '16, 14:53

Hi Gary, Did you notice the existance of these pages ? https://wiki.openstreetmap.org/wiki/Multipolygon_Examples The complex ones could be the answer to your problem and question.

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answered 29 Jul '16, 09:07

Hendrikklaas's gravatar image

Hendrikklaas
8.5k178211351
accept rate: 6%

I think I'd only use a multipolygon relation for the lake with a hole for the situation you describe with the lake tags on the relation.

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answered 28 Jul '16, 14:42

EdLoach's gravatar image

EdLoach ♦
18.1k14147262
accept rate: 23%

1

can you point me to an example on OSM ?

(28 Jul '16, 14:45) Rossendale Gary
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question asked: 28 Jul '16, 14:18

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last updated: 29 Jul '16, 09:07

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