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    Re: What time is it?
    From: Trevor Kenchington
    Date: 2004 Nov 10, 10:15 -0400

    Richard Langley wrote:
    > There is more than one GMT. But when used nowadays, GMT usually refers to the
    > standard zone time kept in the United Kingdom and so is exactly the same as
    > UTC (Coordinated Universal Time). Please read my article
    > . A slightly different
    > version is available on the Radio Nederland Web site :
    > .
    > -- Richard Langley
    Thank you for providing solid facts, where so many have recently
    displayed a surprising degree of confusion.
    Could you add one further detail: How does "GPS time" relate to UTC
    and/or the various grades of UT?
    That is: My hand-held GPS provides a time read-out which, in my case, is
    displayed with the hours and minutes conforming to UTC. Should I suppose
    that the display of the seconds exactly follows UTC, UT1, some other UT,
    or else that it wanders about at its own rate? The geometry of GPS
    clearly requires that my unit knows time to very high precision (based
    on the signals that it receives from the atomic clocks in the GPS
    satellites) and I assume that the time displayed to me is the same as
    that used in calculating position, though rounded to the nearest second.
    (Maybe that assumption is wrong.) But is the time broadcast by the
    satellites exactly linked to UTC or something else?
    The reason for asking isn't a fascination with GPS technology but the
    thought that the most convenient way of receiving and displaying time
    signals for regulating a chronometer or deck watch is to fire up the GPS
    and watch the read-out. I would like to be able to monitor the rate of
    my watch on a daily basis, without needing a phone line or a short-wave
    receiver, and the GPS would seem to allow that -- if the time it
    displays is one or the other kind of GMT or at least within one second
    of it.
    Trevor Kenchington
    Trevor J. Kenchington PhD                         Gadus{at}iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
                         Science Serving the Fisheries

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