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Re: FW: 249 v 229 , Starpath, time tick
From: Richard B. Langley
Date: 1999 Mar 15, 08:34 EST
From: Richard B. Langley
Date: 1999 Mar 15, 08:34 EST
Reminder: For info on the various forms of UT, atomic time and civil time (which is atomic-time based), see my article on GMT and UT available on various Web servers including <http://www.rnw.nl/realradio/features/html/time.html> -- Richard Langley Professor of Geodesy and Precision Navigation P.S. The time indicated by a GPS receiver on its screen may be a fraction of a second delayed due to receiver microcomputer task scheduling. On Mon, 15 Mar 1999, Rick Emerson wrote: >craig@XXX.XXX writes: > > Actually, the GPS (satellite) time is off by about 12 seconds. Each > > manufacturer corrects for this inside the unit. Accuracy may be affected by > > internal errors, but I'm sure it's accurate enough for celestial navigation. > > > >Er, the correct answer is "it depends". Some receivers make the >adjustment between ...what?... UTC1 and UTC2. While I probably have >the names swapped, one's "atomic time" and one's "star" or civil time. >The former is so accurate that it can detect small variations in the >Earth's rotation which is the basis for the latter. The cumulative >error is the difference between the time as determined by various >atomic clocks and the time as determined by timing transits. >Adjustments are added or subtracted on the last day of June or >December. A second was added at 23:59:60 on 31 Dec. 1998, for >example. > >Anyway, the point is that the difference is known and some receivers >display atomic time and some display civil time. The only sure way to >know what a given receiver does is to compare its time with WWV or >WWVH. > >Rick >S/V One With The Wind, Baba 35 > >=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-= >=-= TO UNSUBSCRIBE, send this message to majordomo@XXX.XXX: =-= >=-= navigation =-= >=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-= > =============================================================================== Richard B. Langley E-mail: lang@XXX.XXX Geodetic Research Laboratory Web: http://www.unb.ca/GGE/ Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142 University of New Brunswick Fax: +1 506 453-4943 Fredericton, N.B., Canada E3B 5A3 Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/ =============================================================================== =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-= =-= TO UNSUBSCRIBE, send this message to majordomo@XXX.XXX: =-= =-= navigation =-= =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=