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It is fairly common for an administrative boundary to follow the course of a river. Should the river and the boundary be:

  1. The same way multiply tagged
  2. Overlapping ways

asked 18 Feb '12, 11:34

RobChafer's gravatar image

accept rate: 0%

edited 20 Feb '12, 13:40

srbrook's gravatar image


I suspect it depends:

Is the boundary defined as following the course of the river, or is it defined separately using a series of coordinates that happen to be where the river once was?

Where the boundary really does follow where the river is now, is it really in the middle of the river or on one bank of it?

How do you know where the boundary is with respect to the river, when boundaries often aren't marked on the ground?

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answered 20 Feb '12, 10:42

SomeoneElse's gravatar image

SomeoneElse ♦
accept rate: 16%

In the case I had on the map, the boundary followed the course of a small river. However there are lots of cases where the boundary roughly matches the river (probably because its way isn't very accurate).

(20 Feb '12, 10:52) RobChafer

I can see plenty of examples locally where rivers aren't where they used to be - either because they've naturally moved as time goes on, or they've been culverted across industrial land.

In a case where the river and boundary happen to be in more or less the same place, how do we know how the beoundary is defined?

(20 Feb '12, 11:15) SomeoneElse ♦

The best solution is the first one.

If you have a river or something similar, you can add boundary=administartive or =postal_code or whatever you need.

On the first look, there is no sufficient information about this question in the OSM wiki about boundaries ... maybe we have to add some hints there.

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answered 18 Feb '12, 12:07

stephan75's gravatar image

accept rate: 6%

Thanks stephan75.

(18 Feb '12, 15:54) RobChafer

I would use first method and if editing in potlach2 the follow command "f" will after clicking a couple of nodes it will follow that way,which is great for long common boundaries see

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answered 18 Feb '12, 20:08

andy%20mackey's gravatar image

andy mackey
accept rate: 4%


AFAIK boundaries are usually relations so if the boudary is defined to be the river, why not just add it as a multipolygon member.

(20 Feb '12, 11:42) LM_1

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question asked: 18 Feb '12, 11:34

question was seen: 4,763 times

last updated: 20 Feb '12, 13:40

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum