On 10/08/11 09:09, cook michael wrote:
Le 10/08/2011 07:41, Attila Kinali a écrit :
On Fri, 15 Jul 2011 05:57:45 +0000
"Poul-Henning Kamp"<[email protected]> wrote:
Everybody but the time-lords have always been told to stay away from
TAI in the strongest possible terms by said time-lords, who again and
told the world to use UTC.
May i ask what the reason was to stay away from TAI?
I mean, it is obvious (for me) that for any application that needs
a steady, continious and monotone clock that TAI is one of the best
alternatives among all those time standards.
Attila Kinali
There are all manner of time scales , and each has its use so there is
no need to keep away from any. Just pick that which suits your
application. I think that Poul-Henning was just indicating in a humorous
manner his dislike of the unilateral imposition of a non uniform scale,
UTC, as the transmitted time standard. So if you want a uniform scale,
take TAI. You can get TAI from GPS time by adding 19secs. A number of
GPS receivers can be configured to report GPS time rather than UTC.
Well, the "ban" on TAI has resulted in several "TAI-like" time-scale,
such as the GPS time-scale (with nominally 18 second GPS-TAI difference
as I recall it). Several such scales has been produced as a result of
the ban. Now there is a drive to turn the UTC into one of those
time-scales too. What is driving the use of such time-scales is however
not political but technical, and it would have been much better if they
would all had been using the TAI scale to start with.
Besides, SMPTE has defined the SMPTE Epoch such that all sample-rates,
carriers etc. for TV and audio had a common phase of 0 degree at
1958-01-01T00:00:00Z, and since then effectively follows TAI.
So, the time-lords will have to come up with a pretty good reason why
one should not use TAI, if handwaving and just saying so is just a poor
excuse. They should be happy that we do not use EAL, which is the
internal time-scale.
Cheers,
Magnus
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