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This started as a follow-up to @Hendrikklaas 's question: Direction in waterways

I'm trying to map and display the one-way water canals in Venice (Italy) - there are many of them. I added the tag oneway=yes on a canal, hoping that arrows would show-up on the map (like the ones one-way streets), but they didn't.

Venice is a very particular city... Being in a lagoon, the water only flows with the high or low tides, twice a day, but the movement of water is very negligible. It does however have about a hundred canals, which work like "car" roads. Some are one-way: "traffic is only allowed to go one way", and this is the most important information to display at the moment, some are open to private traffic only at certain times of the day, some have restricted access, some are only open to rowing boats, there are speed limits and some have a maximum width limit etc...

There is a general consensus that the water traffic is poorly documented, and a lot of people go around with their personal boat, and the absence of an updated online map is what got me to try and make it clearer on OSM, but Venice seems so unique that the options might not implemented yet, or hard to figure out.

By the way, some mentioned OpenSeaMap in another question , but Venice's canal network is much closer to a standard road network than open sea navigation.

Any ideas if this is even possible? I couldn't find info on that on the wiki (and did search for a while...). And if one-way canals aren't implemented, do you have any suggestions on how to put the information on the map, with a comment or something like that?

--I'm new to OSM, hope I'm doing this right!

asked 25 Mar '16, 13:50

GDDR's gravatar image

accept rate: 0%

There is a sense in which adding oneway=yes to a canal implements it. Once the information is in the data, someone can take it and use it in a map or for navigation. Of course that doesn't help when no software uses the information, but there's no problem with just starting adding sensible information to the data.

The tiles shown on do not currently utilize it. Canals have been discussed some:

(the openstreetmap-carto project is the style for those tiles)

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answered 25 Mar '16, 14:49

maxerickson's gravatar image

accept rate: 32%

Yes, I think it does make sense to use the "oneway" tag on waterways when the traffic direction is in one way only.

With waterways, the direction of the waterway way (from start to end) is what shows the water flow direction, so (to give an example) this way flows from here to here. If the traffic direction is in the direction of the water flow, "oneway=yes" makes sense. The values used with the "oneway" key in OSM can be seen here, and so if the traffic direction is in the opposite direction to the water flow, "oneway=-1" would be the way to tag it.

With regard to the second part of your question, I don't have an immediate answer. There's a long list of OSM-based services here, and a couple of entries in there mention "waterways". If nothing there fits, then you're going to have to create your own map in order to see the traffic flow direction on waterways, and how you do that depends on what sort of map you want - something to print on paper, a "slippy map" for a website, or something to view on e.g. a mobile phone or satnav or handheld navigation device?

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answered 25 Mar '16, 19:17

SomeoneElse's gravatar image

SomeoneElse ♦
accept rate: 16%

(28 Mar '16, 11:51) yvecai

@yvecai No - would it be possible to describe what it is? It's not obvious from the link (other than it's a map showing some water features).

Is there an issues list for it anywhere (I just noticed that their link to the WTFPL is misspelt)?

(28 Mar '16, 11:59) SomeoneElse ♦

There are oneway arrows on Rio San Vio.

(towards the bottom of the linked view)

(28 Mar '16, 15:28) maxerickson


(28 Mar '16, 16:54) aseerel4c26 ♦

@maxerickson Indeed, but it seems to show a very small subset of waterways.

(29 Mar '16, 22:58) SomeoneElse ♦

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question asked: 25 Mar '16, 13:50

question was seen: 4,391 times

last updated: 29 Mar '16, 22:58

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum