[LEAPSECS] Metrologia on time

Tom Van Baak tvb at LeapSecond.com
Thu Aug 4 01:27:38 EDT 2011

> As I think we've discussed, there are some systems which

> cannot handle |DUT1|>0.9 (UK broadcast time, for example).

A number of national timecodes provide DUT1 to one decimal
place. Over here WWV and WWVB are examples. During the
era when sextants were used and when observatories got their
DUT1 information over shortwave radio, this was important.

The question is -- does anyone use this any more? I'd guess
that any person or any system that needs DUT1 has long since
switched over to telephone, fax, or the internet to obtain this
information. The last LF or SW radio that decoded DUT1 was
made decades ago.

The internet is faster, more reliable, and far more global than
LF or short-wave timecodes ever were. Further, you now get
4 or 5 digits of precision instead of just 1, as well as history
and predictions tens or hundreds of days in advance. All with
one line of code and a URL.

So regardless of what happens with leap seconds, I vote that
the lonely DUT1 digit no longer be updated in timecodes.

Few tears were shed when GOES went away. Or Loran-C. Or
CHU. Or pop-corn. Or when analog TV time/frequency went
off the air. It's time for DUT1 at 1 baud to make its exit as well.

If you want to play it safe perhaps NIST could freeze DUT1 in
WWV/WWVB at its current value of -0.3 until someone calls to
ask if there's a problem. If years go by before anyone has an
issue, then that answers the question. (Note the DUT1 sign bit
is still required to distinguish positive/negative leap seconds).

After that issue is settled, then permitting DUT1 to temporarily
spill over 1.0 seconds is the next hurdle.


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