And all this goes to prove is that: A man with one clock knows what time it is; A man with two clocks is never quite sure. :)
On 29 March 2010 00:58, Arnold Tibus <[email protected]> wrote: > The answer looks to me a bit difficult reading the USNO definition : > > INTERNATIONAL TIME SCALES AND THE B.I.P.M. > http://tycho.usno.navy.mil/bipm.html > > citing: > "...the U.S. Naval Observatory timescale, UTC(USNO), > and its real-time implementation, Master Clock #2 (MC #2), > are kept within a close but unspecified tolerance of the > international atomic timescale published > by the Bureau International des Poids et Mesures > (International Bureau of Weights and Measures [BIPM]) > in Sevres, France." > > "...Hence, all these atomic timescales are called > Coordinated Universal Time (UTC), of which USNO's > version is UTC(USNO)." > > "...The difference between UTC (computed by BIPM) and any other > timing center's UTC only becomes known after computation and > dissemination of UTC, which occurs about two weeks after the fact. > This difference is presently limited mainly by the long-term frequency > instability of UTC. > UTC(USNO) has been kept within 26 nanoseconds of UTC during > the past year through frequency steering of our Master Clocks to our > extrapolation of UTC." > > So I do understand that BIPM is the world's time keeper, but there > may be a difference between the UTCs of up to 26ns? > > "...Since synchronization is never perfect, we provide the latest data > below on the differences between UTC and the UTC of other timing > centers, including USNO,..." > and > "...All of our reference clocks are real-time approximations of UTC(USNO), > and as such are denoted UTC(USNO,MC). Master Clock #2 (MC #2) is > our official reference clock..." > > So I understand this as, that the USA do refer to the time reference > of USNO - and the rest of the world to BIPM directly? > > Since dec. 2009 the PTB in Braunschweig, Germany (with the new > CSF2) and the BIPM in Sevre are the only countries running 4 of the > most precise primary Cs fountain clocks, if I am informed correctly. > Together they should run quite close to the time defined by BIPM I think, > and according our law our official time is transmitted by the PTB. > > Now, How do I have to interprete the readout of GPSDOs like > Trimble's Thunderbolt and others PPS difference in ns to UTC? > > To which UTC? I suppose to the time transmitted by the US GPS SATs. > Is there another difference in UTC to BIPM included? > What is with Glonass (and will be later perhaps with Galileo)? > > In fact the use of GPS is already spreaded all over the world and > in use in many technical applications, meaning that the world does > refer to UTC given by US GPS !? > > Does it make sense under this circumstance as Time Nut to go > below the Xns (26ns ?) frontier as absolute measure? > Will this ever be possible? (Everything is relative...) > > But excuse me in case I do miss and misunderstand something > fully... > > Arnold, DK2WT > > > On Sun, 28 Mar 2010 22:29:22 +1300, Steve Rooke wrote: > >>What puzzles me is who is the keeper of "legal time" for the other >>93.4% of land mass and 95.5% of population of the World other than the >>US. > >>On 28 March 2010 04:49, David Forbes <[email protected]> wrote: >>> At 11:11 AM -0400 3/27/10, Bob Camp wrote: >>>> >>>> I would bet that if you went deep enough into the details, that the Army >>>> at some point was less than enthusiastic about having to ask the Navy when >>>> ever they wanted to know what time it was. >>> >>> My guess is that the Army just asked Western Union, who asked the Navy. >>> >>> -- >>> >>> --David Forbes, Tucson, AZ >>> http://www.cathodecorner.com/ >>> > > > > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Steve Rooke - ZL3TUV & G8KVD A man with one clock knows what time it is; A man with two clocks is never quite sure. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
