[Tagging] Coastline for rivers, estuaries and mangroves?

Christoph Hormann osm at imagico.de
Fri Sep 7 11:33:21 UTC 2018


On Friday 07 September 2018, Joseph Eisenberg wrote:
> But I am uncertain what to do with the waterway=river in the case of
> tidal channels and the complex connections between rivers in these
> mangrove areas. A search of taginfo did not find an alternative tag,
> although river=tidal is in use. I think there should still be a
> waterway midline for the large tidal channels in the mangroves which
> can be used by boats or even ships, to help navigation software.
> (Many of these channels were actually created by flowing river water;
> the rivers in this area meander strongly and often change the
> location of the mouth, as can be seen by comparing the current
> situation to 100 year old Dutch maps)

There is no requirement of river lines to end at the coastline - plenty 
of situations where this is not the case and the documentation also 
explicitly mentions the possibility:

https://www.openstreetmap.org/way/5005576
https://www.openstreetmap.org/way/487506679
https://www.openstreetmap.org/way/550322860

This only applies for the seaward continuation of a river, for a tidal 
channel without any significant freshwater inflow waterway=river would 
be wrong - like here:

https://www.openstreetmap.org/way/401730961
https://www.openstreetmap.org/way/401730966
https://www.openstreetmap.org/way/570038402

This - just like polygon mapping of similar features:

https://www.openstreetmap.org/way/559890030
https://www.openstreetmap.org/way/559890031
https://www.openstreetmap.org/way/425143314
https://www.openstreetmap.org/way/425186522
https://www.openstreetmap.org/way/291218813

can be considered label placement mapping without any real verifiable 
meaning.  If you want to map such things with a geometry other than a 
node you should first create a verifiable definition of the geometry 
(which seems hard) - otherwise you always end up with this kind of 
label drawing.

-- 
Christoph Hormann
http://www.imagico.de/



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