[Tagging] How to tag small canals?

Christoph Hormann osm at imagico.de
Thu Aug 16 16:19:44 UTC 2018

On Thursday 16 August 2018, Martin Koppenhoefer wrote:
> >
> > All of this together has its origin in the fact that in the UK and
> > other early OSM countries large artificial waterways are almost
> > always for navigation and small artificial waterways are almost
> > always for transporting away undesirable water.
> +1
> That’s my analysis as well. What do you think, shouldn’t we fix the
> wiki to make it more universally applicable to all kinds of
> waterways?

As usual i don't think you can change the definition of tags that are 
already used hundreds of thousands of times except by extending their 
scope which would make the tags more vague than they already are.

What would make sense is to explicitly mention that waterway=canal does 
not have a lower size.

Inventing a separate tagging scheme for irrigation systems might be an 
option too but irrigation is performed in very different ways in 
different parts of the world so it might not be too easy to create an 
universal tagging system for that.

> The canal definition was changed in March 2018, before it said to use
> canal only for „the largest waterways created for irrigation
> purposes“

Yes, that was the obvious attempt to expand the narrow scheme to other 
parts of the world in a superficial way oriented at the standard style 
rendering but not at the actual semantics.

Going this route would essentially mean turning all of ditch/drain/canal 
into one big uniform catch-all.  Removing the above is the attempt to 
salvage some of the semantic value in the data.  Not sure how 
successful that is without support from the standard style though.

Unfortunately waterway=canal has only 13k combinations with width=* and 
only 1.8k combinations with usage=* at the moment.  Extending that 
would be the best way to move forward IMO.

Christoph Hormann

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