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

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.

Hungerburg · 2024-07-07T16:03:20.764Z

Further reduced result set overpass turbo – Looking at returned data found me this Way: ‪Movran‬ (‪1286897875‬) | OpenStreetMap

Hungerburg · 2024-07-07T21:30:30.266Z

PS: The feature is quite a bit interesting, Movran - Wikipedia – The fine article talks about a siphon, but from looking at videos, I cant believe that. The pressurised waterways are copied from bing imagery.

Kai_Johnson · 2024-07-08T14:49:50.714Z

The challenge with Movran or any of these subterranean waterways is finding enough information to be able to map them. Often we just have the inlet and outlet and little to no information about the nature or location of the waterway.

It would be very interesting to find a scientific paper that describes the supposed siphon at Movran. But without a verifiable source, we would just be guessing.

yvecai · 2024-07-08T16:59:07.189Z

You’re absolutely right when you say we often don’t know what happens down there.
However we used to map forests from landsat, so we know we can deal with some generalization.

Duja · 2024-07-08T21:08:20.642Z

For an extra-complicated, naturally subterranean but artificially dammed, piped and redirected waterflow, see Trebišnjica, in the same karst region as Movran.

I gave up making the heads and tails of that.

Kai_Johnson · 2024-07-09T00:07:53.819Z

I’m certainly guilty of connecting the inlet and outlet of an underground stream with a straight line. In the absence of more detailed source data, it’s better than nothing.

amapanda_ᚐᚋᚐᚅᚇᚐ · 2024-08-08T15:37:44.048Z

amapanda_ᚐᚋᚐᚅᚇᚐ:

I remove loops and cycles, and I figure basically every “only gravity” waterway only has water going downhill. I know water is often pushed uphill. But I’d like to be able to exclude them.

I analysed recent OSM data, and if I include waterway=pressurized then there are only 22 more loops than with the current approach of ignoring them. There are ~16,100 waterway loops in OSM now. So +22 isn’t a lot. This shows that OSMers aren’t causing many

Here’s a GeoJSON of the “new loops” when you include =pressurized.

In comparison, someone recently asked for waterway=ditch to be included. Although the wiki says ditches should be mapped how the water flows, there are 28,000 loops in waterway=ditch alone!

Based on this, I will probably put =pressurized back into WWM’s “flowing water” category.