[LEAPSECS] Metrologia on time

Ian Batten igb at batten.eu.org
Fri Aug 5 05:02:04 EDT 2011

On 4 Aug 2011, at 16:10, Warner Losh wrote:


> The error grows with DUT1, so using UTC to navigate, point telescopes, etc becomes harder. Systems that used to ignore DUT1 errors since they were small would need to be updated. Other than navigation by sextant though, I'm not aware of too many things that are DUT1 sensitive that don't get DUT1 from somewhere.

Taking a sight with a sextant involves recording the time at the precise moment the sight was taken. That's going to be +/- 1s at best, owing to the resolution of the timing device, and that in turn is going to be +/- 1s owing to the UTC/UT1 delta. So sextant navigation is already coping with +/- 2s. Wikipedia (yeah, I know) says that navigation to +/- 1nm is good going. Circumference of the earth is 21600nm, so 1nm is (presumably, I'm guessing here) equivalent to 4s. It sounds to me like publishing DUT1 on an annual basis would be more than good enough, and people who do sextant navigation would just know to set their watches accordingly. It could be broadcast as part of the shipping forecast.

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