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    Re: GPS as a time authority
    From: Lu Abel
    Date: 2009 Sep 14, 20:45 -0700

    The problem with the accuracy of GPS time displays is usually due to the 
    time it takes for them to internally process the data and display it.  
    This can take several seconds (although I've never heard of >5 seconds), 
    especially on older GPS units with non-multichannel receivers and slow 
    microprocessors.   All this leads to the GPS display being slow.   If 
    anyone on this list has experience with a GPS display being fast, that 
    would be worth noting.
    JKP@obec.com wrote:
    > I think this has been dicussed before, but I'd like to be refreshed on the list's opinion:
    > While assisting the Race Committee at a regatta this weekend, I heard the 
    timekeepers say that they were using "GPS time."  I noted that my $79 
    wristwatch, which I check monthly against the US Bureau of Standards atomic 
    clock (ph: 303-499-7111) and which doesn't lose a second per month, was 8 
    seconds ahead of the Committee's time.
    > I later checked the time shown on my hand-held Gartmin GPS receiver, and it 
    agreed with my watch.  The watch was also still in sync with the Bureau's 
    atomic clock.
    > Question:  Is the time displayed by GPS receivers considered a reliable and 
    spot-on source, up to the requirements of accurate celnav?  I would think 
    that it would be, since the GPS network depends on accurate tracking of the 
    satellites' position at a given time, yet there was that 8-second 
    discrepancy.  Perhaps the Race Committee were simply careless about setting 
    theior clockby GPS.
    > Any thoughts, List Members?
    > -John Parsons
    > >
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