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    Re: Rockwell to Develop GPS Backup
    From: Lu Abel
    Date: 2015 Oct 15, 20:34 +0000
    I doubt they achieve accuracy down to an actual picosecond  (10^-12 seconds).

    Perhaps a more accurate statement would be "sub-nanosecond" accuracy.

    Light travels about a foot per nanosecond.   So a nanosecond timing inaccuracy means your position is off by at least a foot (I say "at least" because there are many sources of inaccuracy, some dependent on timing, and they can add up).  A foot (or a yard or a meter) may not sound like much, but IIRC there are some military needs for a foot or less of accuracy in order to "pry the lid off the can" of heavily armored weapons. 


    From: Bob Goethe <NoReply_Goethe@fer3.com>
    To: luabel{at}ymail.com
    Sent: Wednesday, October 14, 2015 5:57 PM
    Subject: [NavList] Re: Rockwell to Develop GPS Backup

    >Can anyone shed some light as to why is important to a achieve picosecond time synchronization?
    I don't know if I NEED millimeter-accuracy in a navigation system (and aparently, picosecond timing is required to get that millimeter-accuracy).
    But if I ever go for a ride in one of these "driverless cars" I keep reading about, it will make me *feel* better if I think it is anticipating its location vis-a-vis the shoulder of the road to millimeter accuracy.
    BOB




       
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