RfC: Deprecate use of "waterway=pressurised" on anything not artificially built

Venefilyn · 2024-07-03T22:01:48.094Z

InfosReseaux:

Given problem is siphon can be artificial too.
That’s why I still don’t understand why we should put natural/artificial distinction into waterway value instead of surrounding structure.

If we put it on the surrounding structure we need to do a lot more computational stuff to check what everything is. It’s easier if it’s already on the area

InfosReseaux:

Why

waterway=pressurised => artificial

waterway=siphon => natural

could be clearer than

waterway=pressurised +

tunnel=flooded => artificial

natural=cave (or karst or anything related to geology with holes) => natural

?

For me it’s because pressurized indicates it is intended to be pressurized. So either for pumping against gravity, to generate electricity, or other related things. But if it is not sealed and it’s powered by gravity, I don’t see why siphon wouldn’t work for natural and artificial

For what you linked I don’t see what makes it a siphon vs a pressurized pipe. To me it looks like a pipe network that just happens to go above ground there

Kai_Johnson · 2024-07-03T22:59:21.177Z

Venefilyn:

waterway=siphon (or similar tag) - primarily for naturally occurring sealed underground waterways

I would be interested to learn about these natural siphons. Where do such features exist? Under what conditions do these features form?

Venefilyn · 2024-07-03T23:28:09.331Z

I would imagine caves like this

1750×1700 335 KB

Kai_Johnson · 2024-07-03T23:46:47.312Z

Ok. But are there specific examples that are documented well enough that they could actually be mapped in OSM?

UKDiver · 2024-07-04T04:25:42.814Z

Water pipes are pressurised for other reasons than generating electricity, or other related things.

yvecai · 2024-07-04T04:40:56.521Z

OpenStreetMap

Way: ‪Orbe inférieure‬ (‪1111533314‬)

OpenStreetMap is a map of the world, created by people like you and free to use under an open license.

I’m pretty sure the local speleo organization could help refining the way geometry, at least near the cave entrance.

InfosReseaux · 2024-07-04T09:41:27.292Z

Hello

Hungerburg:

I would appreciate something, that mappers can reliably tag without an engineering degree.

I face this argument since the very beginning.
Dedicating tags to one feature and combine them is way more consistent than mixing many concepts on the same tag.
Figures upside shows it’s not a problem to use waterway + tunnel + usage while mapping.

Venefilyn:

If we put it on the surrounding structure we need to do a lot more computational stuff to check what everything is. It’s easier if it’s already on the area

We are dealing here with ways only, the “surrounding structure” is carried by tunnel=* or natural=*. The only required computing is to look for the appropriate tag.

Venefilyn:

For me it’s because pressurized indicates it is intended to be pressurized. So either for pumping against gravity, to generate electricity, or other related things. But if it is not sealed and it’s powered by gravity, I don’t see why siphon wouldn’t work for natural and artificial

It would require to redefine waterway=pressurised, for artificial part at least to exclude siphons from it.
A global movement to reduce the cluttering of waterway=* has started years ago (and many work remains to be done), we’d better not split too much existing values as well.
Well, waterway=natural_siphon would work, even if i’m not so keen on it.

Venefilyn:

For what you linked I don’t see what makes it a siphon vs a pressurized pipe. To me it looks like a pipe network that just happens to go above ground there

It crosses a valley and the bottom pipe is overground over the river, so it’s definitely a siphon.
See this example : File:Waterway siphon duct.JPG - OpenStreetMap Wiki

dieterdreist · 2024-07-04T12:03:33.000Z

Well, waterway=natural_siphon would work, even if i’m not so keen on it.

would this really be suitable? I would think of a siphon similar to a bridge or a tunnel, it doesn’t change the way itself, like we do not have highway=bridge it could be siphon=yes (or maybe =natural/artificial?)

InfosReseaux · 2024-07-04T12:55:29.456Z

I completely second that, obviously.
But the original proposal is to get rid of waterway=pressurised for natural siphons, so which waterway=* value should we use in combination with siphon=yes?

yvecai · 2024-07-04T15:18:39.080Z

Waterway=underground_x or subterranean_x , x being river, stream would work with siphon=yes.

Kai_Johnson · 2024-07-04T15:28:28.484Z

For what it’s worth, we have some remarkable siphons along the Colorado River Aqueduct.

Screenshot 2024-07-04 at 8.17.21 AM1631×577 170 KB

This is a siphon crossing a wash at 34.0680006, -115.0330675. The wash is clearly the lowest point in the surrounding terrain, but the aqueduct siphon goes under it and resurfaces in the canal on the other side at higher elevation than the wash. (The aqueduct flows right to left in this picture.)

Edit: It seems like it might be worthwhile to make the distinction between this type of structure and penstocks or pump-driven pipelines.

On the topic of underground waterways:

yvecai:

Waterway=underground_x or subterranean_x , x being river, stream would work with siphon=yes.

I’d rather see waterway=river/stream combined with location=underground than coin new tag values to combine the two.

yvecai · 2024-07-04T18:36:35.483Z

I wouldn’t be amazed if this would have a single value

But as long as we agree, why not. I’d like to be able to tell the ‘natural’ aspect, which is not conveyed well enougb by [quote=“Kai_Johnson, post:55, topic:115222”]
waterway=river/stream combined with location=underground
[/quote].
Sorry, edited and added a negative

Hungerburg · 2024-07-04T21:45:11.103Z

I’m going to update topic topic. Some examples been brought forward in here.

Hungerburg · 2024-07-04T21:48:49.759Z

yvecai:

Way: ‪Orbe inférieure‬ (‪1111533314‬) | OpenStreetMap

I’d consider that fine as is: A waterway=river, underground. The tunnel looks wrong to me. It is a series of caves, isn’t it?

yvecai · 2024-07-05T04:04:31.531Z

Yes, the water infiltrates (from the knowledge available to date) from the lakes at SO, then forms an underground river (and siphon) in a cave. Part of that cave is a tourism attraction.
And yes, culvert=tunnel sound strange here. We definitely want to devise a common tagging scheme.

Kai_Johnson · 2024-07-05T14:33:10.098Z

Unfortunately, the tagging for caves is not well established or we might have something better for this case.

There are 255 instances of natural=cave and 448 instances of tunnel=cave. And because the proposal for natural=cave never went forward, the wiki page on caves doesn’t provide clear guidance between the two.

Personally, I would prefer natural=cave over tunnel=cave because tunnel seems like something that has been constructed. And natural=cave allows us to map caves that are not tunnels.

So, the tourist part of the example above might be natural=cave with highway=footway, waterway=stream, level=-1. (Some people might prefer to tag the highway and waterway on coincident ways, but I’d prefer to combine them in this case because you’re walking in the stream.)

dieterdreist · 2024-07-05T22:35:17.000Z

Personally, I would prefer natural=cave over tunnel=cave

+1 to natural=cave

yvecai · 2024-07-06T03:57:39.082Z

In the case the cave is not completely flooded, you can barely tag the waterway with natural=cave or tunnel=cave anyway.
Look at this drawing from the cave here

commons.m.wikimedia.org

File:Plan grotte vallorbe.svg - Wikimedia Commons

Unfortunately the course of the river is not on this drawing, but it flows through the blue areas.
Should we go indoor micro-mapping on this, there would be a natural = cave area, a river, lakes, siphons, some paths, steps, bridges, man_made tunnels, lit=yes on some, etc…
The question remains, how to tag the river?
I’d go for waterway=underground_river or waterway=subterranean_river, news values for which the wiki definitions would emphasise the natural aspect.

Hungerburg · 2024-07-07T12:29:10.689Z

I am still at a loss, if there is any actual use to deprecate at all. Are there people that consider waterway=pressurised correct for mapping underground rivers in caves?

@InfosReseaux The waterwaymap.org issue turned out a misunderstanding?

Kai_Johnson · 2024-07-07T14:48:04.829Z

I did not find any uses of waterway=pressurised applied to underground rivers in caves in an informal survey. But I did not look at every instance where the tag was used.