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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@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
                      http://home.istar.ca/~gadus

   

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