Re: [LEAPSECS] Risks of change to UTC

From: M. Warner Losh <imp_at_BSDIMP.COM>
Date: Fri, 20 Jan 2006 22:17:19 -0700 (MST)

In message: <43D1650B.1000301_at_usa.net>
            James Maynard <james.h.maynard_at_USA.NET> writes:
: M. Warner Losh wrote:
: > In message: <43D15F4C.5_at_usa.net>
: > James Maynard <james.h.maynard_at_USA.NET> writes:
: > : ones position using sight reduction tables. Today a mechanical watch or
: > : chronometer, or a battery-powered wristwatch, can be set to UTC using
: > : radio time signals. Then when power fails, the sailor still has a
: > : reasonably accurate spprodximation to UT1 available.
: >
: > If DUT1 is broadcast, then one can set the time keeping device to UT1
: > by a means similar to setting it to UTC, even if DUT1 exceeds 0.9s
: > with a similar accuacy (or better). There's nothing that says a watch
: > has to display UTC to be set correctly.
: >
: > Warner
: >
: > .
: >
: And how is DUT1 to be broadcast in a language-independent manner? That
: protocol needs to be established well in advance.

I should add that I read your 'can be set to utc using radio time
signals' to mean something like WWV or other radio time service.
Those sevices do already broadcast DUT1. Any watch that is smart
enough to decode those signals would be smart enough to add this minor
correction as well.

The mechanical watch might be a bit of a problem, but DUT1 doesn't
change enough to introduce navigation errors similar to what we have
today over the course of a year and can easily be looked up like
someone would lookup what the weather was going to be like.

I'd also add that GPS receivers today already do exactly this sort of
correction when they decode the GPS time, but display the UTC time.

Warner
Received on Fri Jan 20 2006 - 21:19:10 PST