[tz] Coordinated Universal Time (UTC) to retain “leap second”
Brian.Inglis at systematicsw.ab.ca
Fri Nov 20 16:58:32 UTC 2015
On 2015-11-20 00:50, Marshall Eubanks wrote:
> On Fri, Nov 20, 2015 at 12:16 AM, Random832 <random832 at fastmail.com <mailto:random832 at fastmail.com>> wrote:
> On 2015-11-20, Paul Ganssle <paul at ganssle.io <mailto:paul at ganssle.io>> wrote:
> > At least they seem to be deferring decision rather than
> > actively deciding in favor of leap seconds. Still, is anyone
> > actually advocating in favor of leap seconds? Who is being
> > helped by keeping mean solar time at noon UTC or whatever the
> > point of leap seconds is?
> I got into an argument about this with ESR (in an NTPsec
> announcement thread on his blog) a few months ago and he said:
> > You think a timescale which is an integer number of seconds
> > offset from TAI and which is within a second or so of London’s
> > Mean Solar Time is wholly unnecessary. This demonstrates that
> > you aren’t a marine navigator, an astronomer, or (where it
> > bites especially hard) an aviator. It’s from these people that
> > the real-world pushback against decoupling international
> > standard time from mean solar is coming, and they have good
> > reasons.
> So, those people, I guess. It's still not entirely clear to me
> why they need civil time coupled to it, but there you go.
> The only reason (at least, until UT1-TAI builds up to 2 or 3 hours) is celestial navigation using civil time, which should be good to half a km or so just using UTC clock time.
500m would miss a harbour entrance or runway and could land you on the rocks or fly you into a mountain.
Nav, survey, timing software dealing with locations and times assumes an earth centered reference.
Problems telecomms utilities have dealing with leap seconds seem pretty insignificant compared to impacts on legal, finance, and transportation standards, regulations, industries, cargo, and passengers.
Also the judges, lawyers, politicians, financiers, and electorate in many jurisdictions expect time to be mean solar, delta political standard/daylight time offsets, and technical leap seconds, wherever it does not still explicitly mandate an offset to GMT (which still includes much of the Commonwealth, former colonies, and nations traditionally allied to the UK).
> Note, by the way, that the Navy is worried about hacks to the navigation infrastructure sufficiently to make celestial mechanics a required course once again at the Naval Academy.
Doh! Might be good to have some backup when ECM or a missile takes out your antennae, power, storage, ...! Navies should be run to expect to do more than just show the flag, launch planes/helos, or deliver marines.
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
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