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    Re: GPS as a time authority
    From: Lu Abel
    Date: 2009 Sep 15, 11:25 -0700

    If aircraft cockpit displays are showing the wrong time, I would suspect 
    it's due to the same problem (delay in processing and updating time 
    information) that started this discussion rather than their displaying 
    GPS time instead of UTC.   As Richard pointed out, the GPS to UTC 
    correction factor is broadcast by the satellites, so there's no reason 
    that a GPS receiver can not accurately display UTC (with the possible 
    exception of a period of time after a cold start, as Richard points out).
    antoine.m.couette@club-internet.fr wrote:
    > Dear Richard and Lu,
    > True, you did pick it right, I should have written UTC also !
    > Thank you for your interesting insight on all the data displayed in the GPS message !
    > Since in civilian A/C, the cockpit watches are often directly fed by the 
    on-board GPS receiver (uncorrected to UTC to the best of my knowledge : at 
    least this is what I have noticed on the DC10-30's and B757/767's I have 
    flown while watching increasing differences between GPS time and UT over the 
    elapsing years) I was not aware of all the nice features which are part of 
    the GPS messages, including advance notice about the upcoming leap seconds.
    > Thank you again, and hello to the Navlist Forum
    > Antoine
    > Antoine M. Couette
    > >
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