On Thu 2010-08-05T14:55:25 -0600, M. Warner Losh hath writ: > in the UK there's not a clear distinction between GMT and UTC and > often (but not always?) the terms are used interchangeably.
Listen to the BBC. Many of the readers will announce that it's "X o'clock GMT" when that means "X o'clock British Summer Time". > Evidently, the 0 meridian (as defined by > GPS) don't fall precisely where it used to, so the observatory that > made the measurements is a little off. The RGO was moved from Greenwich to Herstmonceux in 1957, and that included the operational meridian circle. From that date there has been no device capable of authoritatively defining the meaning of GMT as specified by the IMC. In the interim there were many changes, the first ones described in the BIH Annual Report for 1968 http://www.ucolick.org/~sla/leapsecs/BIHAR1968.JPG This table refers to 3 changes of conventions which caused global discontinuities in latitude, longitude, and/or UT1. (The longitudes changed again on 1984-01-01 with the switch to FK5 that reset the prime meridian to match the satellite Doppler ranging which was already being performed at the time of this publication, but that switch demanded continuity of UT1, as did the subsequent changes of 1997-02-27 and 2003-01-01.) Nobody can say what GMT means in a manner that requires anyone else to agree. -- Steve Allen <s...@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99855 University of California Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
