[Tagging] [tagging] Canoe route / nautical channels

Christoph Hormann osm at imagico.de
Tue Jul 3 12:26:56 UTC 2018

On Tuesday 03 July 2018, osm.tagging at thorsten.engler.id.au wrote:
> A waterway=canal, waterway=river, or waterway=stream way inside a
> lake or pond is probably appropriate to connect an in-flow to an
> out-flow in a direct line, to allow software to easily trace
> waterways through lakes or ponds (which are essentially just widening
> of the waterway) without having to process areas. In this case the
> waterway going through the larger body of water should share a node
> with the outline of the lake at the in-flow and out-flow points where
> they way and the outline intersect.

Connecting waterways through lakes based on flow has been a subject of 
dispute for a long time.  It is highly unlikely that there will ever be 
full agreement on this and even less that this will manifest in 
mapping.  It often boils down to questions like 'Does the Rhone flow 
through Lac Laman or does it enter into Lac Laman and exit again on the 
other side'.

But all of this is something completely separate from the question how 
to map verifiable navigation routes within lakes.

Note a very practical reason not to use the waterway key for mapping 
navigation routes within lakes is that mapping a navigation route that 
coincidences with a river/canal running through and being mapped 
through a lake is much simpler because you can just use an additional 
tag instead of a separate geometry.

Christoph Hormann

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