[time-nuts] Loran-C & French Clocks

Lux, James P james.p.lux at jpl.nasa.gov
Tue Mar 17 21:43:57 UTC 2009

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Ralph Smith
> Sent: Tuesday, March 17, 2009 12:05 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Loran-C & French Clocks
> Not exactly the case.  Radio components of the ADS-B system 
> require 100 ns accuracy.  Multilateration systems also 
> require very precise timing between components.  The 
> navigation and communications systems are most definitely not 
> looking at the hands of a mechanical watch.
> Ralph
> On Tue, March 17, 2009 9:06 am, Lux, James P wrote:
> > The latter is probably because air traffic control is 
> basically done 
> > at a resolution of 1 minute (e.g. "Hold at SADLE 
> intersection, expect 
> > release at 32[minutes after the hour]") so the several 
> second offset 
> > between UTC and GPS is immaterial.  You're looking at a mechanical 
> > watch in any case.
> >
> > Jim
> >

Oh, yes, if you consider ATC to include navigation functions.  But the "flight control" kinds of things are done on a substantially coarser time scale. I suppose as automated flight control (collision avoidance, for instance) becomes more common, then tighter timing is required.

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