3 ms·

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 hav

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.
  - jjk166 2y ago
    1 second precision is a lot. A typical quartz resonator will drift by about .5 seconds per day at ambient conditions. In this paper they set the clock with GPS right before flight and they only fly for a few hours, so it's tolerable. But in a GPS denied environment where you can't set the clock right before flight, ie exactly where you are using this instead of gps, clock accuracy will become the dominant factor affecting your accuracy after a few days.
    - littlestymaar 2y ago
      > But in a GPS denied environment where you can't set the clock right before flight First of all I don't think the use-case involves the drones operators being deprived of GPS, but even if they were: you don't need GPS to get sub-second accurate time, any internet connection will do it thanks to NTP. Sure it's not as accurate as GPS, but it's still way more accurate than what you need for this to work. Heck, even sharing time through a phone call would work well enough.

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.
- jjk166 2y ago
  1 second precision is a lot. A typical quartz resonator will drift by about .5 seconds per day at ambient conditions. In this paper they set the clock with GPS right before flight and they only fly for a few hours, so it's tolerable. But in a GPS denied environment where you can't set the clock right before flight, ie exactly where you are using this instead of gps, clock accuracy will become the dominant factor affecting your accuracy after a few days.
  - littlestymaar 2y ago
    > But in a GPS denied environment where you can't set the clock right before flight First of all I don't think the use-case involves the drones operators being deprived of GPS, but even if they were: you don't need GPS to get sub-second accurate time, any internet connection will do it thanks to NTP. Sure it's not as accurate as GPS, but it's still way more accurate than what you need for this to work. Heck, even sharing time through a phone call would work well enough.