[Tagging] Way inside riverbank

Janko Mihelić janjko at gmail.com
Tue Apr 14 09:48:38 UTC 2015

How do you know the direction of water flow if you don't have the way?


uto, 14. tra 2015. 11:45 Torstein Ingebrigtsen Bø <torsteinibo at gmail.com>
je napisao:

> Hi,
> I'm currently importing topological data of Norway to OSM. From the data
> set we have riverbanks; however, we do not have the deepest middle way as
> required by the wiki [1]. This middle line is therefore drawn manually.
> This is a time consuming (and dull) job. For one municipal it takes around
> 5-10 hours to draw all these lines, in Norway we have 428 municipals.
> Drawing all these middle lines will slow down the time to import everything
> dramatical. I am therefore curious of what is the benefits of this line. Is
> it really necessary or is it a "nice to have"?
> Some disadvantages with this middle way are:
> - The line add redundancy. I guess that many add this line such that it is
> inside the multipolygon of the riverbank. Doing so the added data is only
> the direction of the river. (Other tags may be added to the multipolygon.)
> - Sometimes people draw the line wrong or forget to update it when
> updating the multipolygon. I have seen "middle" lines outside of the
> multipolygon (either inside islands or outside of the multipolygon). This
> gives false islands and splitting of islands when rendered.
> - A similar way can be generated, if direction and deepest point is not
> required. This comes as a fact of the first point and removes the
> previously mentioned problem.
> - For routing purposes this is not needed. (I have not seen any practical
> marine navigation/routing implementations yet, either.) Routing algorithms
> may also represent a riverbank as a node (or multiple nodes). The same
> problem occurs for lakes where it is not required to have a middle way for
> routing.
> - The direction of the river is seldom used. The direction of a river is
> seldom (or never?) rendered in any map. It is implicitly shown (e.g., by
> contour lines).
> - Specifically for the import of Kartverket N50 [2], this requirement is
> slowing down the import process dramatical and import of other data of more
> current value are delayed. This is therefore also a question of
> prioritizing data to be imported.
> I therefore propose to make this middle way in riverbanks recommended
> (when the deepest way is known), not required.
> [1] http://wiki.openstreetmap.org/wiki/Tag:waterway%3Driverbank
> <http://wiki.openstreetmap.org/wiki/Tag:waterway%3Driverbank#Old_tagging>
> [2]
> https://wiki.openstreetmap.org/wiki/Import/Catalogue/N50_import_(Norway)
> Best regards,
> Torstein I. Bø
> tibnor
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