On Mon, 29 Mar 2010 08:24:00 +0200, Magnus Danielson wrote: >Tom Van Baak wrote: >>> It also has an option to sync the PPS with GPS or UTC. I thought >>> they were off by an integral number of seconds so I don't expect any >>> change. Does anybody know what's going on here? >> >> The GPS broadcast message includes leap second and >> a0 and a1 terms which are used to forward predict UTC >> from GPS time, which is derived from UTC(USNO). >> >> A0 and A1 are what you'd guess: a phase offset and a >> frequency offset. >> >> See page 157 of the GPS ICD: >> <http://www.navcen.uscg.gov/gps/geninfo/ICD-GPS-200C%20with%20IRNs%2012345.pdf> >> >> >> >> So yes, at the ns level the two 1PPS will differ since UTC >> is not the same as UTC(USNO) or any other UTC(k) for >> that matter. Have you measured it? I would be interested >> to know what the delta is for your receiver today. You >> can also dump out the a1 and a0 corrections with binary >> commands on some GPS receivers. >The GPS time is steered towards UTC(USNO) to be maintained within 1 us. >The effective difference is in a few ns. I could dig up the webpage at >USNO giving the difference if needed to. (TvB already has a mail from me >on this topic)
>There should be no effective difference between them. UTC(USNO)-UTC(BIPM) difference is actually swinging between +- 7ns: http://tycho.usno.navy.mil/gif/tai.gif A good summary showing the differences for the international laboratories UTC-UTC(k) for the past with last date 2010 March 12 ( and a lot more): http://tycho.usno.navy.mil/latestcircT Arnold _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.