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On 6/30/2012 5:36 PM, Robert Bernecky wrote:
> I am under the impression that without the leap second the NA is "more
> wrong", and that the addition of the leap second brings the time error
> to under one second.

That begs the questions as to whether the NA incorporates the leap
second that occurs in a given year in the next year's tables.  It must,
or by now the tables would more than 30 seconds of time off.

As Gary pointed out, cel nav practitioners are working to the whole
second (and lucky to do that without an assistant or jury rig).

As Gary also noted this leap second changes UT1 from plus 0.6 s to minus
0.4 s, so hardly a big deal given the resolution of the entire system.
Technically from "more wrong" to "less wrong."

Of further note, leap seconds traditionally occur years apart, and are
added or subtracted so UT1 is never more than 0.9 s from UTC.
If the trend continues, at some point in the future the difference
between UTC and UT1 will be zero. For that year the the NA will be spot
on part of the time, and perhaps oh-so-slightly wrong (without
correction) the rest of the year.  As the old quip goes, "That's good
enough for government work."

To split hairs, without correction this year's NA is always wrong. Next
year's NA will probably be less wrong, and so on until we get to the
above scenario.

Bill B

   

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