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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Watches as chronometers
From: Geoffrey Kolbe
Date: 2013 Jun 09, 07:30 +0100
There are no leap second adjustments in TAI. Gary was rating his clocks against UTC, which is literally "broadcast time" as he was comparing his clocks against the WWV radio signal.
As for the leap seconds which were inserted during the rating period, see Gary Lapook's posting of 31st May. "I did not allow for the one leap second inserted during the test period on June 30, 2012."
Gary accounted for this by adding the leap second to the calculated error. The main point of my posting was to suggest that when rating clocks over a three year time period then simply adding the number of leap seconds inserted during that period to the calculated error was too simplistic. I argued that this approach would be correct for a short period of, say a few months. I argued that over a period of, say, ten years, then the saw-tooth discontinuities in UTC caused by the insertion of a number of leap seconds would average out and you need not account for leap seconds at all. But where your rating period (three years in this case) is approximately the same as the saw-tooth waveform period in UTC (approximately one year) then how you account for the insertion of a leap second is non-trivial. You did not address this point at all.
Geoffrey Kolbe
From: Geoffrey Kolbe
Date: 2013 Jun 09, 07:30 +0100
Bill B You are correct, my questions were rhetorical. What I was trying to do was to make you think a little about what you had said, and about what you had proposed was a mistake by Gary in not accounting for a leap second. You have obviously gone away and researched "time" and the complexity of all its various standards, so I account that a partial success. But you obviously did not grasp my point about accounting for the insertion of leap seconds in UTC when rating a clock against UTC.If I understand Gary's methodology, he was essentially tracking TAI when rating his digital "chronometer" array. He knew UTC, DUT1, and UT1 when he started. There were no leap seconds during the rating period, but he did monitor DUT1 and adjust for it yielding a uniform time scale. In a nutshell, TAI plus a constant. He could now attempt to predict any drift on a daily basis. (Emphasis by G Kolbe)
There are no leap second adjustments in TAI. Gary was rating his clocks against UTC, which is literally "broadcast time" as he was comparing his clocks against the WWV radio signal.
As for the leap seconds which were inserted during the rating period, see Gary Lapook's posting of 31st May. "I did not allow for the one leap second inserted during the test period on June 30, 2012."
Gary accounted for this by adding the leap second to the calculated error. The main point of my posting was to suggest that when rating clocks over a three year time period then simply adding the number of leap seconds inserted during that period to the calculated error was too simplistic. I argued that this approach would be correct for a short period of, say a few months. I argued that over a period of, say, ten years, then the saw-tooth discontinuities in UTC caused by the insertion of a number of leap seconds would average out and you need not account for leap seconds at all. But where your rating period (three years in this case) is approximately the same as the saw-tooth waveform period in UTC (approximately one year) then how you account for the insertion of a leap second is non-trivial. You did not address this point at all.
Geoffrey Kolbe