5 ms·

I wonder if GPS and the like will be used more for their clock features than for position. The emissions celestial bodies are perfect fiducial markers [0,1], bu

by adolph 2y ago

I wonder if GPS and the like will be used more for their clock features than for position. The emissions celestial bodies are perfect fiducial markers [0,1], but connecting them to position still requires accurate timekeeping [2], as the paper notes: Provided the use of an accurate clock, the results presented in this paper will not degrade over time. 0. https://www.twz.com/17207/sr-71s-r2-d2-could-be-the-key-to-winning-future-fights-in-gps-denied-environments https://www.twz.com/17207/sr-71s-r2-d2-could-be-the-key-to-w... 1. https://timeandnavigation.si.edu/multimedia-asset/nortronics-nas-14v2-astroinertial-navigation-system https://timeandnavigation.si.edu/multimedia-asset/nortronics... 2. https://www.rmg.co.uk/stories/topics/harrisons-clocks-longitude-problem https://www.rmg.co.uk/stories/topics/harrisons-clocks-longit...

KineticLensman 2y ago
They are perfect markers only as long as you can see them. Clouds and fog are your enemies here
- mpenet 2y ago
  That. However that works just fine for ICBMs and the like… The future is more likely to be quantum accelerometers and quantum gyroscopes, as they have no “external dependency”.
  - cyberax 2y ago
    More likely image-based navigation, where you just upload the entire imagery of the route and then use it to correct your inertial references. Encrypted positioning information from low-orbit satellites is another option.
    - mpenet 2y ago
      That doesn't work well in some conditions, it's not new either. Some cruise missiles that have TFR (Terrain-following radar) and actually do this already. It also is not really applicable when you are on a balistic course at *very* high altitude, course correction has to happen early in these case given the reentry speed/constraints.
- all2 2y ago
  I presume radio signal or certain frequencies of thermal would be viable for adverse weather conditions.
  - the__alchemist 2y ago
    The frequencies used in GPS: Yes. The frequencies used for celestial nav: No.
rich_sasha 2y ago
I guess timekeeping is relatively easy? These systems would only operate independently for a few hours tops. I would imagine even a standard quartz movement would be accurate enough.
- GJim 2y ago
  > I guess timekeeping is relatively easy...... would imagine even a standard quartz movement would be accurate enough. Good Lord! How wrong can you get! Very precise timing (often taken from GNSS for convenience) is needed for much of the modern word, from IP, cellular and DAB networks, to AC phase matching the electrical mains grid. Quartz clocks are nowhere near accurate enough for these purposes. This government report makes very sobering reading: https://www.gov.uk/government/publications/satellite-derived-time-and-position-blackett-review https://www.gov.uk/government/publications/satellite-derived... TLDR: Our dependence on GNSS for timing almost dwarfs that for navigation. And we urgently need to consider using backups (be that local atomic clocks, or long wave time signals).
  - withinboredom 2y ago
    I mean, considering celestial navigation was a thing long before we had accurate clocks… I’d venture they aren’t wrong at all. Or did you forget that people have been doing celestial navigation by hand for over two millennia?
    - jjk166 2y ago
      Celestial navigation actually drove the development of accurate clocks https://timeandnavigation.si.edu/navigating-at-sea/longitude-problem https://timeandnavigation.si.edu/navigating-at-sea/longitude... Quartz clocks didn't overtake chronometers in terms of accuracy until the mid 20th century, and chronometers will still beat regular crystals like you'd find in cheap electronics.
      - littlestymaar 2y ago
        > Celestial navigation actually drove the development of accurate clocks That's true, but that still doesn't change the fact that you don't need nanosecond precision for this purpose. At the equator, 1 second precision gives you roughly 500m accuracy, which is already much higher than what the celestial imagery allows here (4km in the paper). Clearly this method isn't limited by clock accuracy at all.
Animats 2y ago
The clock accuracy required for celestial navigation is on the order of seconds, not microseconds.

by adolph 2y ago

KineticLensman 2y ago

They are perfect markers only as long as you can see them. Clouds and fog are your enemies here

mpenet 2y ago
That. However that works just fine for ICBMs and the like… The future is more likely to be quantum accelerometers and quantum gyroscopes, as they have no “external dependency”.
- cyberax 2y ago
  More likely image-based navigation, where you just upload the entire imagery of the route and then use it to correct your inertial references. Encrypted positioning information from low-orbit satellites is another option.
  - mpenet 2y ago
    That doesn't work well in some conditions, it's not new either. Some cruise missiles that have TFR (Terrain-following radar) and actually do this already. It also is not really applicable when you are on a balistic course at *very* high altitude, course correction has to happen early in these case given the reentry speed/constraints.
all2 2y ago
I presume radio signal or certain frequencies of thermal would be viable for adverse weather conditions.
- the__alchemist 2y ago
  The frequencies used in GPS: Yes. The frequencies used for celestial nav: No.

rich_sasha 2y ago

I guess timekeeping is relatively easy? These systems would only operate independently for a few hours tops. I would imagine even a standard quartz movement would be accurate enough.

GJim 2y ago
> I guess timekeeping is relatively easy...... would imagine even a standard quartz movement would be accurate enough. Good Lord! How wrong can you get! Very precise timing (often taken from GNSS for convenience) is needed for much of the modern word, from IP, cellular and DAB networks, to AC phase matching the electrical mains grid. Quartz clocks are nowhere near accurate enough for these purposes. This government report makes very sobering reading: https://www.gov.uk/government/publications/satellite-derived-time-and-position-blackett-review https://www.gov.uk/government/publications/satellite-derived... TLDR: Our dependence on GNSS for timing almost dwarfs that for navigation. And we urgently need to consider using backups (be that local atomic clocks, or long wave time signals).
- withinboredom 2y ago
  I mean, considering celestial navigation was a thing long before we had accurate clocks… I’d venture they aren’t wrong at all. Or did you forget that people have been doing celestial navigation by hand for over two millennia?
  - jjk166 2y ago
    Celestial navigation actually drove the development of accurate clocks https://timeandnavigation.si.edu/navigating-at-sea/longitude-problem https://timeandnavigation.si.edu/navigating-at-sea/longitude... Quartz clocks didn't overtake chronometers in terms of accuracy until the mid 20th century, and chronometers will still beat regular crystals like you'd find in cheap electronics.
    - littlestymaar 2y ago
      > Celestial navigation actually drove the development of accurate clocks That's true, but that still doesn't change the fact that you don't need nanosecond precision for this purpose. At the equator, 1 second precision gives you roughly 500m accuracy, which is already much higher than what the celestial imagery allows here (4km in the paper). Clearly this method isn't limited by clock accuracy at all.

Animats 2y ago

The clock accuracy required for celestial navigation is on the order of seconds, not microseconds.