[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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