5 ms·

Would there be a reason why GPS with 10m accuracy is OK but Galileo with 1m is not?

nickpsecurity 10y ago
GPS has better than 10m accuracy in another operating mode. Only the military is allowed to use that one, though. Then they don't want Galileo being 1m accurate? Probably same military reasons.
- wcoenen 10y ago
  > GPS has better than 10m accuracy in another operating mode. Only the military is allowed to use that one, though. This has not been true since May 2000, when GPS "Selective Availability" was turned off. Civilian and military receivers have the same accuracy now. http://www.gps.gov/systems/gps/modernization/sa/ http://www.gps.gov/systems/gps/modernization/sa/
  - nickpsecurity 10y ago
    I didnt know about that. Thanks for thd tip. So, the civilian GPS devices have the PPS signal and accuracy the military had?
  - DashRattlesnake 10y ago
    No, that's not true. The military has access to different codes and frequencies that aren't available for civilian use, which can be used to apply further corrections to the computed location. Selective Availability was not the only difference between civilian and military GPS. https://www.quora.com/Is-there-any-difference-between-military-GPS-data-and-civilians-in-terms-of-accuracy https://www.quora.com/Is-there-any-difference-between-milita...
    - nickpsecurity 10y ago
      Those extra frequencies were what I was thinking about. If they're still closed, then military still cripples GPS. The points of military vs civilian for this discussion would still apply.
    - wcoenen 10y ago
      As far as I understand, the remaining differences between military and civilian GPS don't matter much for accuracy. The military may still have the advantage of ionospheric correction, but civilians can use other augmentation systems like WAAS[1] with similar results. I think the military signals are mostly intended to protect against signal spoofing and jamming. [1] https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System
      - nickpsecurity 10y ago
        Thanks for that link. Never heard of it. That's some mind-blowing tech and accuracy.

GPS has better than 10m accuracy in another operating mode. Only the military is allowed to use that one, though. Then they don't want Galileo being 1m accurate? Probably same military reasons.

wcoenen 10y ago
> GPS has better than 10m accuracy in another operating mode. Only the military is allowed to use that one, though. This has not been true since May 2000, when GPS "Selective Availability" was turned off. Civilian and military receivers have the same accuracy now. http://www.gps.gov/systems/gps/modernization/sa/ http://www.gps.gov/systems/gps/modernization/sa/
- nickpsecurity 10y ago
  I didnt know about that. Thanks for thd tip. So, the civilian GPS devices have the PPS signal and accuracy the military had?
- DashRattlesnake 10y ago
  No, that's not true. The military has access to different codes and frequencies that aren't available for civilian use, which can be used to apply further corrections to the computed location. Selective Availability was not the only difference between civilian and military GPS. https://www.quora.com/Is-there-any-difference-between-military-GPS-data-and-civilians-in-terms-of-accuracy https://www.quora.com/Is-there-any-difference-between-milita...
  - nickpsecurity 10y ago
    Those extra frequencies were what I was thinking about. If they're still closed, then military still cripples GPS. The points of military vs civilian for this discussion would still apply.
  - wcoenen 10y ago
    As far as I understand, the remaining differences between military and civilian GPS don't matter much for accuracy. The military may still have the advantage of ionospheric correction, but civilians can use other augmentation systems like WAAS[1] with similar results. I think the military signals are mostly intended to protect against signal spoofing and jamming. [1] https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System
    - nickpsecurity 10y ago
      Thanks for that link. Never heard of it. That's some mind-blowing tech and accuracy.