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    Re: Navigation without Leap Seconds
    From: Paul Hirose
    Date: 2008 Apr 15, 20:53 -0700

    Lu Abel wrote:
    > If the celestial data in the
    > almanac were calibrated in leap-second-less time, no correction would be
    > required.  But if my watch somehow showed leap-second-less time while
    > the Almanac used them, then I'd have to know how many leap seconds had
    > occurred since 1972 (the year leap-seconds were adopted).
    My guess is that if leap seconds are abolished, the first scenario will
    play out. The Nautical Almanac could be tabulated in terms of UTX
    (that's what I'll call the new time scale), with the tabulated GHAs
    based on predicted UT1-UTX. (The IERS already predicts UT1-UTC a year
    into the future.) You'd enter the almanac with UTX (a whole number of
    hours offset from local civil time), extract GHA, and apply longitude to
    obtain LHA, as we do today.
    Fixes will have a longitude error due to the discrepancy between the
    actual UT1-UTX vs. the predicted value. However, we tolerate greater
    error today. The almanac is tabulated in UT1, but most navigators simply
    use UTC because a few tenths of a second aren't significant in ordinary
    celestial navigation.
    I don't think the second scenario will come to pass. Historically, when
    a new time scale is created, it coincides with an existing one, e.g.,
    GPS time and UTC. So UTX will probably be equal to UTC when (if) it
    comes into effect. Deleting the leap seconds accumulated since 1972
    would require a large forward step adjustment.
    I block messages that contain attachments or HTML.
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