[Tagging] Question about waterway=pressurized

Kyle Hensel K.y.l.e at outlook.co.nz
Tue Sep 14 22:51:01 UTC 2021


I think a tag like tunnel=siphon would be useful for inverted siphons. Siphon are distinct from culverts and flooded tunnel, which are currently the only defined values of tunnel=* for waterways.
Would it be worth making a proposal for tunnel=siphon?

> Do you have real example of working siphon please?
Inverted siphon: https://basemaps.linz.govt.nz/#@-43.6544667,171.5589171,z16.5592

Non-inverted siphon: I understand correctly, they would always be tagged as a pipeline.
Here’s a temporarily setup one: https://youtu.be/ZUsTT_RUEdQ?t=299 Watch from 4:59 to 6:15


Kyle

From: Volker Schmidt<mailto:voschix at gmail.com>
Sent: Wednesday, 15 September 2021 04:26
To: Tag discussion, strategy and related tools<mailto:tagging at openstreetmap.org>
Subject: Re: [Tagging] Question about waterway=pressurized

Here in the Po Valley we have hundreds (or mor) of inverted siphons. They do not need and, to my knowlege, do not have pumps. Many or max be most of them are not (yet) correctly tagged in OSM. This most likely due to the fact that waterway data are imports and it looks as if the original did not distinguish between waterway junctions and underpasses.
I am not aware of any example of an uninverted siphon.


On Tue, 14 Sep 2021, 17:42 François Lacombe, <fl.infosreseaux at gmail.com<mailto:fl.infosreseaux at gmail.com>> wrote:
Hi Volker

>From my understanding, both siphon and inverted-siphon are pressurised.
Siphon uses suction to pull water downstream which implies a positive pressure in its middle, without air.

This is an interesting concept we could classify with additional tags dedicated to siphons.
Some pumps use this principle to raise level of a liquid (see pump_mechanism=siphon https://wiki.openstreetmap.org/wiki/Key:pump_mechanism)

Do you have real example of working siphon please?
I only seen inverted siphons (mainly for sewage under roads or rivers) in the past.
This is the bottom of an inverted siphon (maybe 3m in diameter) to make water cross a valley https://www.openstreetmap.org/way/405871631

All the best

François

Le mar. 14 sept. 2021 à 17:12, Volker Schmidt <voschix at gmail.com<mailto:voschix at gmail.com>> a écrit :
Question to François: is an inverted-siphon (botte sifone, pont-siphon) piece of waterway to be mapped as pressurised?

On Tue, 14 Sep 2021, 16:18 François Lacombe, <fl.infosreseaux at gmail.com<mailto:fl.infosreseaux at gmail.com>> wrote:
Hi Kyle,

Le mar. 14 sept. 2021 à 03:24, Kyle Hensel <K.y.l.e at outlook.co.nz<mailto:K.y.l.e at outlook.co.nz>> a écrit :
 Is there are reason why waterway=pressurized is used instead of waterway=river/stream/canal/drain and pressurized=yes?

Yes, waterways are defined according to their permanent flowing regime. Some are free flowing, others are pipe flowing.
A given waterway can't be both as it requires a special prerequisites to handle pressurised water.
https://wiki.openstreetmap.org/wiki/Waterways#Artificial_waterways:_pressurised_vs_Open-flow_Waterways

This table gives all values according to their regime
https://wiki.openstreetmap.org/wiki/Key:waterway#Values

River, streams, canals and drains are defined as free flowing waterways, so it wasn't consistent to propose pressurised=yes for them.
If a river goes punctually in a permanent pressurised culvert, waterway=pressurised + tunnel=culvert sounds the most appropriate possibility.
By the way, a river relation can obviously involve sections with different regimes.

In a perfect world we would have cleared waterway=* from all other values than flowing regime (move waterway=pier or waterway=fuel to man_made or amenity).
Never mind, I go back sleeping :)

All the best

François
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