[ntp:questions] Re: May ntp be off by a second in case of GPS source?

David Schwartz davids at webmaster.com
Thu Dec 29 19:54:02 UTC 2005


""Komka Péter"" <KomkaP at prolan.hu> wrote in message 
news:43B2E284.5080207 at prolan.hu...
(If anyone cares:)

>As I know, 1 or 2 seconds have to be added to the stamp's time to obtain 
>current time. Because it took some (not negligable) time to
>- compute the time (in the GPS receiver) (known as "position fix 
>calculation")
>- tranfer the stamp to me.
>(Millisecond part may be separately set via PPS.)

    Every GPS receiver I know has its own internal clock, which it 
synchronizes to the GPS time reference. The time output from the GPS 
receiver is from its internal clock. Although it may take many seconds for a 
GPS receiver to accomplish this synchronization, once the GPS receiver has 
done so, and as long as it remains so, it always knows what the time is at 
any instant.

    DS





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