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Discuss Tag:waterway=canal here:

Lock gates

How are we tagging lock gates then? waterway=lock_gate is already on map features. So the mention of other suggestions here (man_made=lock, lock=*, lock:name=*) is confusing. If waterway=lock_gate is the accepted way to do it, then we'll need to specify whether it's a single node or a length of way which was otherwise canal. (Should have these details on the Tag:waterway=lock_gate page) -- Harry Wood 12:46, 6 May 2008 (UTC)

I tag locks (on small, UK-style waterways) as nodes with lock=yes. A lock de facto has gates at each end, it wouldn't work very well otherwise. --Richard 14:51, 6 May 2008 (UTC)
I've been tagging locks as a short segment of waterway=lock with a node tagged as waterway=lock_gate at each end. The name and number of the lock go on the name= tag for the lock section. Seems to render nicely e.g.
--POHB 08:13, 7 May 2008 (UTC)
hmmm. Two different ways of doing it then. -- Harry Wood 16:20, 7 May 2008 (UTC)



Can a width tag be applied to a canal? I'm asking because an irrigation canal that is about three meters wide is being rendered the same width as a two-lane road. — Val42 05:00, 4 October 2008 (UTC)

Width (in metres) can be added to denote the average width of a canal: width=3 in your case.

maxwidth=* can be used to define the maximum beam of boats able to use the canal which will be determined by pinch points such as aqueducts, bridges and locks. For a canal it probably makes sense to apply it to the whole length given that boats won't be able to travel from end to end because of the beam restrictions. On a navigable river with locks however, it is probably more logical to only apply it to nodes or short sections where there is a width restriction, i.e. a lock channel.


I'm not clear about usage how and for what. We've a canal (Rhine–Main–Danube Canal) here which is about 55 metres wide. But it's narrower e.g. when bridging over streets or before locks and has dents on some places. So it's not possible to get that width and shape right with a line taged as waterway=canal. Also it has tracks attached to both sides which should be done right.

It looks good as poligon tagged as natural=water or waterway=riverbank but that's semantically wrong. So what to do here? I've seen such canals done as a polygone tagged as waterway=riverbank and a path in the middle tagged as waterway=canal. Is that a standard and state of the art?

And what is waterway=canal really for then? --Miriat 15:15, 19 November 2008 (UTC)

I'm also wondering how to tag canal polygons, some experiments here: Talk:Key:water#Prevalence.
"waterway=canal is very common for ways, but there doesn't seem to be much guidance at all about area features. One might argue that waterway=*, highway=*, aeroway=* etc. are all reserved for way features only, not areas, but then we have waterway=riverbank which is already violating that. So maybe waterway=canal is ok for areas after all?" (and let the feature type decide the rendering rules, routing ability, and Xapi extracts) :-/
--Hamish 27 August 2012

I've seen a lot of canals done as the "most relevant" area type (either river lake or an extension of the coastline into the inland area) and a way down the middle tagged as e.g. Manchester Ship Canal. This allows for more complex geometries which many need (esp with branching canals) but does seem a little kludge (can you really call the edges a large branching canal coastline? It's tidal so surely you can't call it a lake and there's no flow so it isn't a river). Coastal areas also have the added disadvantage of only updating on a glacial timescale. --InsertUser 22:02, 30 August 2012 (BST)

Direction of flow

I am not sure about all channels, but many of them don't have direction of flow. It there is any tag, showing the direction of flow or its absense? If no, what about flow_direction=forward/backward/no? Dinamik (talk) 06:49, 2 October 2013 (UTC)

Well we do have a convention for rivers Tag:waterway=river#Direction of flow which is to always point the way arrows in the direction of flow (or put a FIXME tag if we don't know for some reason) It's usually easy to figure out the direction of flow of a river just by looking at what it must be flowing into, but for canals it's not so easy of course. So yeah it would make sense to have an explicit tag indicating that a mapper has thought about it (while all other canals you would assume the way direction is irrelevant). flow_direction=forward makes sense to me, but I'm not a big canal mapper. What do the experts think? -- Harry Wood (talk) 11:29, 4 October 2013 (UTC)
If there are no objections, I add description of flow_direction=forward/backward/no. Also I think, that flow_direction=unknown, perhaps, have sense. Dinamik (talk) 10:03, 16 June 2014 (UTC)

For a valid description we need something likeː

flow_directionːvertex=[###,##m Scheitelhöhe]

Where "source" and "target" may be the name of an oher waterway.
For canals going upwards to a "vertex" from both sides, the canel has to be split at the vertex.

All tries by referencing the OSM-way-direction will be misunderstandable I guess.
What do you think? --Markus (talk) 05:55, 2 September 2015 (UTC)

Service tags

I don't recall seeing any discussion about service=* tags being used to describe canals, and there are no comments about the edit nor any more specific documentation. I have some concerns about this. First, terminology: "hydropower" is apparently a more common term than "water power" (and it wouldn't require an underscore). Second, the proposed selection of services omits some common usages such as potable water (or water being conveyed into a treatment plant where it shall be made potable). Third, the tagging of multipurpose canals is not addressed. T99 (talk) 01:06, 27 December 2013 (UTC)

River vs Canal for canalised rivers?

Does anyone have any ideas on the official or preferred tagging for rivers that have been canalised? Usually these canals follow the course of the river, albeit straightened, and most/all of the river's flow now goes down the new course. There is/was boat traffic on the new course (and often was not possible on the old natural course), however the waterway is still known as a river (or sometimes called the New River X).