From: Ashley Yakeley <ashley_at_semantic.org>
Subject: Re: [LEAPSECS] A lurker surfaces
Date: Tue, 02 Jan 2007 16:40:23 -0800
Message-ID: <459AFB77.1000603_at_semantic.org>
Ashley,
> Magnus Danielson wrote:
> > The budget isn't there and the govrements already pay
> > good money for the systems in place and is looking to get as much out of it as
> > possible.
>
> Yes, you're probably right, they're likely to prefer to patch up
> something ultimately broken cheaply than fix it properly.
>
> I think the best that can be hoped for in the short term is a
> user-created infrastructure among those who care enough to bother. And
> just agreeing what the lengths of the seconds should be, or even the
> schedule for specifying them, is likely to be hard enough.
There is never such a thing as a perfect system in this game. We need to run of
one or another of a whole set of approximation schemes. Whatever scheme we have
or come up with, we have a number of different needs which in themselfs are
conflicting. Whatever system we are running, it needs to be widely realizeable
with sufficient precission as the many different usages require, and there are
many customers around. It also needs to be well understood and supported by
system designs throughout many types of equipment.
Even if we can come up with a "better" scheme for some purposes, it needs to be
manageable into the whole infrastructure in a fairly painless fashion. You can
never get it quite right, but fairly painless is what you can hope fore.
If we rebuilt all time distribution systems and all systems using time, we
could do anything. Including rubber seconds which can be designed handle all
expected rates of earth spinning in the next 10000 years or so. Unfortunatly
that is not a luxury we have. Technological and economical limitations is
there and real. Not that we don't have technological and economical issues as
it is, we do, but that even strengthen the point.
So, I don't think we will get the perfect time solution ever. But behing humans
as we are, we keep striving towards that unobtainable goal.
I would do a whole lot of things differently if time and economics where not a
limiting factor. In the meantime, I too will have to suffer approximations.
> > Indeed. But it was not what you wrote.
>
> Eh, GPS time is TAI. You just have to know about the odd encoding...
In order to know about "the odd encoding" you need to call it something else
than TAI since is not EXACTLY as TAI. It is not even TAI plus some fixed
number. You can make a darn good (given the money you need) TAI approximation
off the GPS time. Another darn good approximation could I have if I plugged
into say PTB-CS2. They are not the same and never will be. You can hower use
the GPS time to getyourself a TAI approximation, but it never will be TAI.
So GPS time is not TAI. Never will be. Given some compensation it is near
thought.
Cheers,
Magnus
Received on Tue Jan 02 2007 - 17:25:01 PST