[time-nuts] 15 Seconds error...??

Tom Van Baak tvb at LeapSecond.com
Wed Jan 18 17:26:51 EST 2012


> Use of TAI is fine, as long as you won't tell anyone near the timelords, 
> as obvious TAI is supposed to be "hands off".

Magnus, Mike,

The issue, I suspect, is that "TAI" still, mostly, in print and in
people's minds, refers to the abstract paper clock, maintained
by the BIPM, rather than some physical realization.

For physical realizations we have all the UTC(k) clocks, one or
sometimes more than one per country. The "UTC" you get from
GPS is a slightly noisy version of UTC(USNO) which itself is a
slightly noisy version of UTC. Depending on your technical or
legal needs you can apply corrections to shift your native GPS
tick to better match the UTC(k) of your choice. For example, I
know NIST uses a GPS CV setup in such a way so that the tick
becomes a UTC(NIST) tick rather than a UTC(USNO) tick.

All this sort of phase manipulation occurs with flavors of UTC
and we're all used to it. So it's convenient when we talk about
"TAI" that it's just the paper clock we're talking about.

On the other hand, when nanoseconds and issues of virtual
or physical clocks don't matter, you can add 34 seconds to
a wrist watch can call it TAI if you want. It's what I do here:

http://www.leapsecond.com/java/gpsclock.htm

/tvb





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