On 2006-01-18, Steve Allen wrote:
> Now I am confused.
>
> By my reading of the documents, ITU-R did not define DTAI until the
> most recent revision of TF.460 in 2002. DUT1 had been defined since
> very early on.
You are right, the name DTAI has apparently been introduced in 2002. It
also appears in [ITU-R TF536.2 2003] and [ITU-R TF686.2 2002]. It is
defined in these documents as the values of TAI - UTC and is described
as the contribution of the IERS to the determination of UTC. Such values
of TAI - UTC are published back to 1972 (step function) and even to 1961
(piecewise linear function).
Since I wanted to describe how I understood Mark Calabretta's
description of UTC as essentially the same as TAI except for the
variable radix notation for the (whole) second field in the time
of day values, I took DTAI as a convenient abbreviation of
TAI - ( UTC value when interpreted with
a fixed radix for the second field )
I avoided writing UTC for TAI - DTAI because this would contradict
the assumption that UTC is just TAI plus additional information.
Hope that clarifies things a bit.
Michael Deckers
