[ntp:questions] how does jitter and round trip time affect the accuracy of the local clock?

David Woolley david at ex.djwhome.demon.invalid
Sun Jun 26 20:35:36 UTC 2011

Richard B. Gilbert wrote:

> very high quality.  In particular, GPS sends a pulse per second and one 
> edge of that pulse is accurate to about +/- 50ns.  The rest of the GPS 
> signal tells you which second is being marked by the specified edge, 
> leading or trailing (I've forgotten which).

GPS doesn't do this.  In fact GPS relies on the fact that there are 
significant time "errors" between the times received from different 
satellites.  It uses pseudo random ranging codes, not single pulses.

Some GPS receivers, synthesize a pulse on the one second mark from their 
solution for the time.

More information about the questions mailing list