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Peter Smith wrote:

> Wait a few minutes after you turn the GPS on. The leap second correction is
> included in a 12.5-minute message cycle, and if your unit hasn't cached it
> from the last time it was on, you'll have to wait until the next time it
> comes around.
>
> The other problem with using a GPS receiver as a time source is that the
> software is rarely designed to make correct time display a priority.
> Updating the display can take a back seat to message processing and position
> computations. I've noticed that my old Garmin 75's time display is a
> noticeable fraction of a second behind the ticks on WWV/CHU. Newer units
> with faster chips my do better.


As of this morning, with a lot less than 12.5 minutes to check the time
(but with long enough to capture multiple satellites), my unit showed a
time approximately one second fast on UTC. After a long day on the water
(the first time in some weeks that it has been on), it seems to be
tracking UTC. I wonder whether a leap second has recently been
introduced to UTC and not considered by my unit until it received the
appropriate code? Or was my unit relying on its internal clock this
morning and didn't check its time until later?

Either way, today's experience seems to support Peter's recommendations.


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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