OpenStreetMap

Wikiproject Rivers

Posted by katpatuka on 15 June 2009 in English (English)

I started to create relations for rivers and opened [[Wikiproject Rivers]]. Added relations are for example Svapa and Seym(1) as well as Desna. I'm not sure how one could add a hierachical system to show the basin system of rivers: for Dnieper one would have to add all sub-relations of tributaries like Desna (1. sub-level), Seym (2. sub-level), Svapa (3. sub-level) and so on...

Ideas are welcome ;-)

(1) Browse http://betaplace.emaitie.de/webapps.relation-analyzer/osm.jsp?relationId=157475

Location: Братів Драгунів вулиця, Dolynske, Сосницький район, Chernihiv Oblast, 16154, Ukraine

Comment from randomjunk on 15 June 2009 at 11:53

Surely this is easy to work with without relations? You can figure it all out from the topology.

A river is a bunch of connected ways, and tributaries are rivers that flow into that.

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Comment from katpatuka on 15 June 2009 at 12:14

What do you mean: "with" or "without relations" ?
The idea is just: make me a map/overlay of the Dnieper river basin with all tributaries... and for that to work I imagine just choosing the Dnieper river relation and enabling the checkbox "with tributaries" and getting a nice rendered map!

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Comment from SK53 on 15 June 2009 at 15:24

Yes it can be done from the topology: if the topology is complete and correct. I've never thought of the process of finding isolated DAGs in a relational database as 'easy' though! Certainly levels in a watershed/river basin would be much better assigned through some automated algorithm. Something will eventually be needed given that we have river, navigable, river, not navigable and stream which doesn't really give enough discrimination for sensible rendering.

I think it's easier to define the boundary (watershed) of a riverbasin, than try and tag all the relevant watercourses appropriately (similar to admin boundaries vs. is_in). Since most watersheds are often features of interest (ranges of hills or mountains) these can be marked with a relation. So perhaps boundary=watershed on a relation would work? OK then you have to find all the watercourses within a bounding polygon, but surely that's trivial. :-)

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Comment from katpatuka on 15 June 2009 at 16:41

So what about waterway=drainage_divide (german Wasserscheide) ? ;-)

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Comment from SK53 on 15 June 2009 at 18:05

Given that the one thing one knows about a watershed is that it is not a water feature, I don't like using this type of tag (anymore than waterway=boatyard). A watershed is really an abstract concept, whereas on the ground there may be a range of features (in hilly or mountainous country we might have natural=ridge), but we may still need waterway|natural=watershed where the lie of the land is not so obvious). Of course the names of tags are merely syntactic sugar - if I want foo=bar to mean something then so be it - so I'm not going to get too hung-up about the specifics. I think the only important thing is to use a relation.

The US has quite a lot of data on watersheds: most available freely. Take a look at US Interactive Watersheds. Mapping them is interesting for all sorts of reasons: pollution, ecology etc. I'm glad someone started the ball rolling.

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