[LEAPSECS] Java JSR-310 TAIInstant class

[Steve Allen]

On 2011 Jan 29, at 14:21, Stephen Colebourne wrote:

> What JSR-310 needs is a single time-scale that has a single

> incrementing number of fixed size units (SI seconds) with no other

> interpretations (such as what a day is). I believe that TAI best meets

> that definition today, and thus is the choice made.


This is what the GPS system designers needed also, but they
recognized that the time on board each satellite vehicle would
not be the same as the time of the GPS system as a whole, and
GPS system time would not be the same as UTC(USNO) modulo leaps,
and UTC(USNO) modulo leaps would not be the same as TAI, and 
that's why they were right to name the GPS system time as
GPS system time, with no pretense that it had any meaning prior
to inception, and to broadcast corrections for the difference
between SV and GPS, and for the difference between GPS and UTC(USNO).

So I caution that JSR-310 is really creating a new time scale which
cannot be extrapolated into the past and which will only cause
confusion by claiming the name TAI when it cannot be TAI.
                                                                                
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Steve Allen               <sla at ucolick.org>              WGS-84 (GPS)
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