NavList:

   

Reply

Thank you, Peter.

I guess I will check my GPS display against the dial-up time signal from
Canada's NRC. If it is tracking UTC, then it presumably will continue to
do so. If it is fast by a good number of seconds, I'll abandon the idea
of using at a time reference.


Trevor Kenchington


Peter Smith wrote:

> GPS time is the number of seconds since 06-Jan-1980 00:00:00.0 UTC, and is
> steered to an accuracy of better than 1 microsecond. It is encoded in the
> GPS NAV message as the number of weeks since 06-Jan-1980 and the number of
> seconds since the start of the week. As such, it does not include leap
> seconds, so a naive reading of GPS time would be fast of UTC today (13 or 14
> seconds, I believe, for the number of leap seconds since 06-Jan-1980).
> However, elsewhere in the GPS messages it gives the correction, so receivers
> can display UTC or UTC-derived zone time.
>
> Interestingly, on 22-Aug-1999, the 10-bit week number field wrapped around
> from 1023 to 0, causing some early GPS receivers to lose track of the date.
>
> The US Naval Observatory's GPS page at http://tycho.usno.navy.mil/gps.html
> has some info.
>
>  -- Peter
>
>


--
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

   

Reply