On Wed 2015-03-04T00:04:10 +0000, Tony Finch hath writ: > They have different epochs: > > TAI: 1958-01-01 T 00:00:00 Z > PTP: 1970-01-01 T 00:00:00 Z > GPS: 1980-01-06 T 00:00:00 Z
Getting meaninglessly pedantic, in Survey Review v19 #143 p7 (1967) A.R. Robins had been talking with Sadler and Smith and with that information in hand he wrote that atomic time was identical to UT2 at 1958-01-01 T 20:00:00 Z This, of course, disagrees with Guinot's memoir, but the various realizations of UT2 then differed by centiseconds and the different versions of atomic time were subsequently realigned by milliseconds. And that date of 1958-01-01 was decided ex post facto at the 1959 August meetings where the US and UK decided to try coordinating their broadcast time signals using cesium. So there really isn't an epoch for TAI. On Tue 2015-03-03T14:31:13 -0800, Hal Murray hath writ: > Since GPS time is a fixed offset from TAI, it's easy to convert. I believe that BIPM would disagree because of the different kinds of steering at the nanosecond level. The stance of the BIPM was expressed in http://www.bipm.org/cc/CCTF/Allowed/18/CCTF_09-27_note_on_UTC-ITU-R.pdf where TAI "should not be considered as an alternative time reference." Without the assent of the BIPM it is hard for there to be an agreed upon name for real-time versions of time scales that are trying to track the value of TAI (which will not actually be available until the next issue of Circular T). -- Steve Allen <[email protected]> WGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m _______________________________________________ LEAPSECS mailing list [email protected] https://pairlist6.pair.net/mailman/listinfo/leapsecs
