[Tagging] How to tag small canals?
osm at imagico.de
Thu Aug 16 14:14:14 UTC 2018
On Thursday 16 August 2018, SelfishSeahorse wrote:
> What is the usual (or sensible) way to tag small canals like mill
> races (example: [^1]) or small irrigation channels (example: [^2]),
> i.e. the small equivalent of waterway=canal?
A bit of information on current meaning of artificial waterway tags:
waterway=ditch and waterway=drain are largely used without a well
defined difference between them. In terms of documented meaning
waterway=ditch is more for features collecting water while
waterway=drain is more for features transporting water. But this is
not a difference you can find consistently being made in actual
mapping. Both tags were invented and are primarily used for waterways
removing undesirable water.
There is also some minor use of waterway=ditch and waterway=drain for
smaller natural waterways because it is rendered slightly thinner than
waterway=stream in the standard style but this is generally accepted to
be abuse of the tags.
waterway=canal is essentially for all open artificial waterways that are
not primarily for transporting away undesirable water (which would be
waterway=ditch or waterway=drain). However since the standard style
renders it in a fairly prominent form with a thick line smaller canals
(like for irrigation purposes) are often tagged differently
(waterway=ditch, waterway=drain or waterway=stream) despite not
qualifying as such. Still waterway=canal is the corrent tagging here,
nothing except the standard style suggests a lower size limit for
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.
Long story short: My recommendation would be tagging waterway=canal and
specifying usage=* and width=*. This might not look ideal on the map
but will allow all data users to correctly interpret the data.
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