NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Rockwell to Develop GPS Backup
From: Lu Abel
Date: 2015 Oct 15, 20:34 +0000
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@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
