Add quest "What is this camera angle ?"

[lounne]

General

Affected tag(s) to be modified/added: camera:angle for a value in degrees.
Question asked: What is this camera angle ?

Mainly asked for camera:type=fixed, but can be added to camera:type=panning with multiple values.

Checklist

Checklist for quest suggestions (see guidelines):

• 🚧 To be added tag is established and has a useful purpose
• 🤔 Any answer the user can give should have an equivalent tagging (SCEE quests may not be answerable in all cases, but please keep this rare)
• 🐿️ A survey is necessary (may require knowledge of the subject, though easy answering for everyone is preferred)
• 💤 Not an overwhelming percentage of quests have the same answer (No spam)
• 🕓 Applies to a reasonable number of map data (Worth the effort)

Ideas for implementation

Element selection:
A field awaiting an angle in degrees.
I don't know if it's possible to suggest app to users but there's a great FOSS app to have a bubble level is https://f-droid.org/fr/packages/com.kylecorry.trail_sense/.
The user should align their phone with the angle of the camera and get the value from there.

Metadata needed:

Proposed UI:

[mcliquid]

How exactly should a user measure this value? Should they always carry a bubble level with you and then align it with the camera?

[lounne]

How exactly should a user measure this value? Should they always carry a bubble level with you and then align it with the camera?

They can use their phone, i should mention the app trail sense again, there is an easy bubble level functionality on it.

[mcliquid]

They can use their phone

And then I hold my mobile phone up to the camera?

https://wiki.openstreetmap.org/wiki/File:Traffic_camera_-_Lake_Albert_Road_and_Sturt_Highway.jpg

And of course I’ll have a ladder with me so I can reach the camera. And of course no one will give me a strange look if I climb a ladder to a public CCTV camera to measure the angle. I suppose I should wear a high-visibility vest.
Joking aside. The Quest isn’t suitable for the app.

[lounne]

No there's a lot of public cameras that you can get their angle with ease from a distance, you just have to tilt your phone to match the angle of the camera. I do it, it is kind of the only way to do it accurately while surveying.
To have this quest is to make the contribution of this data more easy and see which one need this data on the go.

Other way to do it, you go in exact front of the camera on the ground and point your phone with the bubble level to it. The angle is the angle of the camera.

[mnalis]

🚧 To be added tag is established and has a useful purpose

What would be the alleged "useful purpose" though?

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Camera angle by itself is pretty useless -- as far as I can see, it should (at the very least) always be accompanied by mounting height of the camera (and preferably also addition with field-of-view [if known]) which might perhaps then be used to provide camera coverage area, which would be useful), but that has several problems of its own:

• prerequisite for (usefulness of) angle collection (which is very complex in itself) is that camera mounting height¹ is collected first (which is another complexity added).

• for tagging that, sometimes height=* seems to be used, but that is just plain wrong!
  height=* is about "actual height of a feature". So height=2.4 does not mean that the camera is mounted at height of 2.4m above the ground, but that it is some enourmous camera which itself measures 2.4m in vertical dimension (e.g. you've just mapped something similar to Hubble Space Telescope)!

• correct tag to use use would be ele=2.4, but that one is incredibly complex to use for this purpose, as it needs to be specified in HAMSL (height above mean sea level, as defined by the EGM96 geoid model), which user would not normally know, and which is quite different from:

  • HAE (height above the WGS84 ellipsoid) (which GPS might return, but usually with much worse accuracy then the horizontal one, e.g. easily can have errors of few dozen meters -- so it won't help you², as you need centimeter-level precision here for camera angle to be useful).
  • HAGL (height above ground level) which is something user could relatively easily measure with e.g. measuring tape or laser measurement tool between ground and a camera. That one can be theoretically mapped by creating building:part and tagging it with min_height and very low height=*, and then merging camera node on that building part only, but nobody (reasonable) does that AFAIK.³
  • and in any case HAMSL (even if somehow known, e.g. when you're mapping a camera at a mountain peak which had ele tagged⁴ by geodesic surveyor previously) does not usually even attempt to account for centimeter precision required. And it is only useful if ele of the ground where user is standing is also known (Which generally won't be mapped in OSM).

...and there is no way one should expect that any (even SCEE!) users would be anywhere near capable (or willing!) of handling such complexity.

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TL;DR: IMHO, I would think that this quest in particular would be incredible amount of work, requiring exquisite expert knowledge and much time and work on the part of the mapper, to map information of very low usefulness (esp. when compared to all that work).

But I'm open to discussion if someone could explain how such information would be useful and mappable in relatively easy and error-free manner.

Footnotes

1. as well as user height (more precisely, user mobile phone holding height), is some mobile app is to be used to try measurements of height (see problems in e.g. https://github.com/streetcomplete/StreetComplete/issues/2222#issuecomment-3170689795 and around) ↩

2. even while it might be tagged with ele:wgs84, if known ↩

3. one might try to tag min_height directly on camera element to simplify that process somewhat, but there is exactly 1 usage of that worldwide, so not very likely to be supported by anyone either ↩

4. so you can add HAGL to peak's ele to get actual camera mounting point ele which you'd need ↩