3 ms·

Have there been any computer vision systems that can approximate celestial navigation using common sensors like a camera, An electronic compass, and a tilt sens

Have there been any computer vision systems that can approximate celestial navigation using common sensors like a camera, An electronic compass, and a tilt sensor? Something like a computer vision based auto sextant. This is an idea I have thought about for a while but I have zero background in this area.

walrus01 2y ago
I'm not aware of any specifically, but one of the instruments that can be used as a data point to further reduce error when navigating in a zero-GPS/zero-radio-signal environment is an INS. The very highest precision ones are quite classified and used on submarines. https://en.wikipedia.org/wiki/Inertial_navigation_system https://en.wikipedia.org/wiki/Inertial_navigation_system
exe34 2y ago
https://play.google.com/store/apps/details?id=com.embarcadero.CamSextant&hl=en https://play.google.com/store/apps/details?id=com.embarcader... not tried it
Polizeiposaune 2y ago
Not exactly what you're looking for, but spacecraft can use optical star trackers which compare what they see to a catalogue of known stars to determine orientation. See, for instance: https://www.rocketlabusa.com/space-systems/satellite-components/star-trackers/ https://www.rocketlabusa.com/space-systems/satellite-compone... https://en.wikipedia.org/wiki/Star_tracker https://en.wikipedia.org/wiki/Star_tracker
gmueckl 2y ago
The closest unit I can think of right now was the SR-71's celestial navigation unit. I don't know how it worked internally, but it supposedly navigated the spy planes to targets across the globe before GPS existed.
- nine_k 2y ago
  A number of ICBMs used / uses a similar approach. In space, stars are always visible well, and terrestrial navigation aids may have been jammed or destroyed when ICBMs are put to use.
- ttepasse 2y ago
  From one SR-71 memoir I remember the factoid that sometimes the electromechanical star tracker was sensitive enough to catch stars in the daylight while the plane was still on the ground. Makes one wonder what is possible now with modern digital photographic sensors and processing power. And miniaturisation of course, the 60s celestial navigation unit was the size of a fridge.
- bigfatkitten 2y ago
  Many aircraft, mostly numbers had similar systems.
kragen 2y ago
Yes, starcams are standard equipment on satellites including Cubesats because they provide more precise attitude information than any other available sensor. There are numerous free-software packages for star tracking; a quick search finds https://github.com/spel-uchile/Star_Tracker https://github.com/spel-uchile/Star_Tracker. I don't know if there's, like, an Android app that will do the required sensor fusion to tell you where on Earth you are.
deleted 2y ago
[deleted]
cguess 2y ago
Yes, there's one mentioned in the article, STELLA. Here's a paper describing it https://adsabs.harvard.edu/full/1999naos.symp..239K https://adsabs.harvard.edu/full/1999naos.symp..239K
- tgsovlerkhgsel 2y ago
  That's an amazing paper: TL;DR star tracking is a thoroughly solved problem, the hard problem is finding "where is down" without looking at the horizon (which may not be visible). The solution to that is coupling into the ship's inertial navigation system, which still may drift up to an arcminute per hour, but if you feed the star tracker data back into the INS for corrections, it gets better.
  - giraffe_lady 2y ago
    It's wild that the state of art on this is still basically how they left it at the end of the apollo program.
    - zokier 2y ago
      Not sure how you reached that conclusion. The linked STELLA paper describes many post-Apollo improvements, both improvements implemented in STELLA, and star trackers like OWLS and AST 201. And it's not like progress stopped even there; the focus has been mostly on space exploration applications, but as the paper mentions the developments are somewhat applicable for terrestrial use too.
tgsovlerkhgsel 2y ago
I looked into it briefly, and while it may be easy at sea with a horizon reference, it becomes surprisingly hard without it (which also complicates testing). The article touches on this with the mention of the bubble sextant required at night, presumably because you can't see the horizon. You'd have the same problem over land. The stars only give you the angle at which you're looking at the sky. If you know the angle to the center of the earth (or can relate the sky measurement to that) and the exact time, you know where you are, within the inaccuracy of your measurements. Being 1/60th of a degree (1 angular minute) off places you 1 nautical mile off. A bubble sextant solves this by including a literal 2D bubble level. "When properly used, the bubble sextant gives good results, by which we mean an accuracy to within 5 miles." (https://www.usni.org/magazines/proceedings/1939/june/averaging-bubble-sextant-observations https://www.usni.org/magazines/proceedings/1939/june/averagi...). The obvious solution that immediately springs to mind is a tilt sensor/accelerometer. However, once you get to a useful accuracy, those start getting expensive - several hundred dollars for a 0.01 degree system, which would give you an error of about 1 km. You'd then need a sufficiently rigid mount for everything, proper calibration (remember, some angle on your mount being 0.05 degrees off completely destroys all usefulness of your system!), and then a camera and a plate solver (software that turns a photo into sky coordinates) should give you a useful fix. I think you could build a system that gets you within a few nautical miles for about $1000 (parts, not labor).
Havoc 2y ago
Like others said SR71 etc. Problem is those fly high enough that the sky is pretty dark and you can actually see stars. That's not an assumption we can make for the avg plane

walrus01 2y ago

I'm not aware of any specifically, but one of the instruments that can be used as a data point to further reduce error when navigating in a zero-GPS/zero-radio-signal environment is an INS. The very highest precision ones are quite classified and used on submarines. https://en.wikipedia.org/wiki/Inertial_navigation_system https://en.wikipedia.org/wiki/Inertial_navigation_system

exe34 2y ago

https://play.google.com/store/apps/details?id=com.embarcadero.CamSextant&hl=en https://play.google.com/store/apps/details?id=com.embarcader... not tried it

Polizeiposaune 2y ago

Not exactly what you're looking for, but spacecraft can use optical star trackers which compare what they see to a catalogue of known stars to determine orientation. See, for instance: https://www.rocketlabusa.com/space-systems/satellite-components/star-trackers/ https://www.rocketlabusa.com/space-systems/satellite-compone... https://en.wikipedia.org/wiki/Star_tracker https://en.wikipedia.org/wiki/Star_tracker

gmueckl 2y ago

The closest unit I can think of right now was the SR-71's celestial navigation unit. I don't know how it worked internally, but it supposedly navigated the spy planes to targets across the globe before GPS existed.

nine_k 2y ago
A number of ICBMs used / uses a similar approach. In space, stars are always visible well, and terrestrial navigation aids may have been jammed or destroyed when ICBMs are put to use.
ttepasse 2y ago
From one SR-71 memoir I remember the factoid that sometimes the electromechanical star tracker was sensitive enough to catch stars in the daylight while the plane was still on the ground. Makes one wonder what is possible now with modern digital photographic sensors and processing power. And miniaturisation of course, the 60s celestial navigation unit was the size of a fridge.
bigfatkitten 2y ago
Many aircraft, mostly numbers had similar systems.

kragen 2y ago

Yes, starcams are standard equipment on satellites including Cubesats because they provide more precise attitude information than any other available sensor. There are numerous free-software packages for star tracking; a quick search finds https://github.com/spel-uchile/Star_Tracker https://github.com/spel-uchile/Star_Tracker. I don't know if there's, like, an Android app that will do the required sensor fusion to tell you where on Earth you are.

deleted 2y ago

[deleted]

cguess 2y ago

Yes, there's one mentioned in the article, STELLA. Here's a paper describing it https://adsabs.harvard.edu/full/1999naos.symp..239K https://adsabs.harvard.edu/full/1999naos.symp..239K

tgsovlerkhgsel 2y ago
That's an amazing paper: TL;DR star tracking is a thoroughly solved problem, the hard problem is finding "where is down" without looking at the horizon (which may not be visible). The solution to that is coupling into the ship's inertial navigation system, which still may drift up to an arcminute per hour, but if you feed the star tracker data back into the INS for corrections, it gets better.
- giraffe_lady 2y ago
  It's wild that the state of art on this is still basically how they left it at the end of the apollo program.
  - zokier 2y ago
    Not sure how you reached that conclusion. The linked STELLA paper describes many post-Apollo improvements, both improvements implemented in STELLA, and star trackers like OWLS and AST 201. And it's not like progress stopped even there; the focus has been mostly on space exploration applications, but as the paper mentions the developments are somewhat applicable for terrestrial use too.

tgsovlerkhgsel 2y ago

I looked into it briefly, and while it may be easy at sea with a horizon reference, it becomes surprisingly hard without it (which also complicates testing). The article touches on this with the mention of the bubble sextant required at night, presumably because you can't see the horizon. You'd have the same problem over land. The stars only give you the angle at which you're looking at the sky. If you know the angle to the center of the earth (or can relate the sky measurement to that) and the exact time, you know where you are, within the inaccuracy of your measurements. Being 1/60th of a degree (1 angular minute) off places you 1 nautical mile off. A bubble sextant solves this by including a literal 2D bubble level. "When properly used, the bubble sextant gives good results, by which we mean an accuracy to within 5 miles." (https://www.usni.org/magazines/proceedings/1939/june/averaging-bubble-sextant-observations https://www.usni.org/magazines/proceedings/1939/june/averagi...). The obvious solution that immediately springs to mind is a tilt sensor/accelerometer. However, once you get to a useful accuracy, those start getting expensive - several hundred dollars for a 0.01 degree system, which would give you an error of about 1 km. You'd then need a sufficiently rigid mount for everything, proper calibration (remember, some angle on your mount being 0.05 degrees off completely destroys all usefulness of your system!), and then a camera and a plate solver (software that turns a photo into sky coordinates) should give you a useful fix. I think you could build a system that gets you within a few nautical miles for about $1000 (parts, not labor).

Havoc 2y ago

Like others said SR71 etc. Problem is those fly high enough that the sky is pretty dark and you can actually see stars. That's not an assumption we can make for the avg plane