Re: A lurker surfaces

2007-01-03 Thread Zefram
Daniel R. Tobias wrote: It's a few seconds off from TAI, isn't it? It was synchronized to UTC in 1980 (I think), Yes. The epoch for GPS time is 1980-01-06T00:00:00 UTC, which is 1980-01-06T00:00:00 GPS time. Not having leap seconds, it effectively tracks TAI, with the equation

Re: A lurker surfaces

2007-01-03 Thread Zefram
Magnus Danielson wrote: TA(GPS) = GPS + 19 + C0 No, there is no TA(GPS). TA(k) are distinct timescales that AFAICT generally do not attempt to track TAI. Presumably they are intended as maximally stable frequency standards, not steering to maintain long-term interval accuracy, like TAI itself.

Re: A lurker surfaces

2007-01-03 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Zefram writes: Would have been nice. Actually, since the only real significance of GPS time is that it's part of the signal format, they could just as well have picked an unconventional but space-efficient encoding (say, 32-bit count of seconds, wrapping every 4

Re: A lurker surfaces

2007-01-03 Thread Tony Finch
On Tue, 2 Jan 2007, Steve Allen wrote: And, yes, explaining all this is very hard. It's not obvious to the geek that the political and funding realities are more real than the underlying physics, but that's the way the world works. I've been reading The Measurement of Time by Audoin and

Re: A lurker surfaces

2007-01-03 Thread Tony Finch
On Sun, 31 Dec 2006, Rob Seaman wrote: But actually, I think we should call leap seconds what they are - intercalary events. Yes! I also liked Zefram's comment As a calendar, UTC is presently of the observational variety. http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg01367.html

Re: A lurker surfaces

2007-01-02 Thread Zefram
Ashley Yakeley wrote: I'd like to see an elastic civil second to which SI nanoseconds are added or removed. Perhaps this could be done annually: at the beginning of 2008, the length of the civil second for the year 2009 would be set, with the goal of approaching DUT=0 at the end of 2009. This was

Re: A lurker surfaces

2007-01-02 Thread Ed Davies
Zefram wrote: ... The historical trend is towards using uniform time units. It seems curious now that when the atomic clock was invented astronomers opposed calling it a time standard. Well, it seems curious to everybody except Rob Seaman :-) ... It is much like the ancient Egyptians (IIRC)

Re: A lurker surfaces

2007-01-02 Thread John Cowan
Zefram scripsit: Projecting into the future, one can foresee the eventual abandonment of timezones in favour of the universal use of Universal Time. I think that's over the top. Bureaucratically it is just too annoying if the large majority of people have a work shift that overlaps legal

Re: A lurker surfaces

2007-01-02 Thread Ashley Yakeley
On Jan 1, 2007, at 22:56, Steve Allen wrote: Then let's improve the infrastructure for communicating the best estimation of earth orientation parameters. Then in a world of ubiquitous computing anyone who wants to estimate the current rubber-second-time is free to evaluate the splines or

Re: A lurker surfaces

2007-01-02 Thread Warner Losh
Then let's improve the infrastructure for communicating the best estimation of earth orientation parameters. Then in a world of ubiquitous computing anyone who wants to estimate the current rubber-second-time is free to evaluate the splines or polynomials (or whatever is used) and come

Re: A lurker surfaces

2007-01-02 Thread Ashley Yakeley
On Jan 2, 2007, at 05:15, Zefram wrote: A technical issue: broadcast time signals are phase-locked with the carrier, which is at some exact number of hertz. If the time pulses are every civil second, and that is now 1.00015 s (as it was in 1961), it can't be synchronised with the (say) 60

Re: A lurker surfaces

2007-01-02 Thread Ashley Yakeley
On Jan 2, 2007, at 11:40, Warner Losh wrote: The second technical problem is that the length of a second is implicitly encoded in the carrier for many of the longwave time distribution stations. 10MHz is at SI seconds. For rubber seconds, the broadcast would drift into adjacent bands reserved

Re: A lurker surfaces

2007-01-02 Thread Ashley Yakeley
M. Warner Losh wrote: GPS is also used for UTC today. Many ntpd's are stratum 1 tied to a GPS receiver. I imagine two parallel time infrastructures, one synchronised to TAI, the other to rubber mean universal time. Stratum 0 devices for the latter would probably have to use radio. So, sure,

Re: A lurker surfaces

2007-01-02 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Ashley Yakeley writes: M. Warner Losh wrote: GPS is also used for UTC today. Many ntpd's are stratum 1 tied to a GPS receiver. I imagine two parallel time infrastructures, one synchronised to TAI, the other to rubber mean universal time. Stratum 0 devices for the

Re: A lurker surfaces

2007-01-02 Thread Ashley Yakeley
Magnus Danielson wrote: The detailed introduction of the frequency corrections in various sources was different, and getting a coherent view of where UTC actually where was difficult. Since then we have grown to depend on UTC transmission to a higher degree than we did back then. Infact, for

Re: A lurker surfaces

2007-01-02 Thread Magnus Danielson
From: Ashley Yakeley [EMAIL PROTECTED] Subject: Re: [LEAPSECS] A lurker surfaces Date: Tue, 02 Jan 2007 15:21:14 -0800 Message-ID: [EMAIL PROTECTED] Ashley, Magnus Danielson wrote: The detailed introduction of the frequency corrections in various sources was different, and getting

Re: A lurker surfaces

2007-01-02 Thread Ashley Yakeley
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

Re: A lurker surfaces

2007-01-02 Thread Magnus Danielson
From: Ashley Yakeley [EMAIL PROTECTED] Subject: Re: [LEAPSECS] A lurker surfaces Date: Tue, 02 Jan 2007 16:40:23 -0800 Message-ID: [EMAIL PROTECTED] Ashley, Magnus Danielson wrote: The budget isn't there and the govrements already pay good money for the systems in place and is looking

Re: A lurker surfaces

2007-01-02 Thread Daniel R. Tobias
On 2 Jan 2007 at 12:40, Warner Losh wrote: The interval math in UTC that's hard today would be significantly harder with rubber seconds. But it is just software, eh? In short, it is an interestingly naive idea that was tried in the 1960's and failed when there were only dozens of high

Re: A lurker surfaces

2007-01-02 Thread Daniel R. Tobias
On 2 Jan 2007 at 11:47, Ashley Yakeley wrote: The obvious solution is to transmit rubber time on a rubber frequency. Are rubber duckies involved? -- == Dan == Dan's Mail Format Site: http://mailformat.dan.info/ Dan's Web Tips: http://webtips.dan.info/ Dan's Domain Site:

Re: A lurker surfaces

2007-01-02 Thread Daniel R. Tobias
On 2 Jan 2007 at 11:56, Ashley Yakeley wrote: GPS is TAI. I'm not proposing abandoning TAI for those applications that need it. It's a few seconds off from TAI, isn't it? It was synchronized to UTC in 1980 (I think), but without subsequent leap seconds, so it's now different from both TAI and

Re: A lurker surfaces

2007-01-02 Thread Rob Seaman
Magnus Danielson wrote: If you do want a new timescale, I think rubber seconds isn't going to be the solution. One might point out that many time scales do rely on rubbery seconds, e.g., sidereal time and apparent solar time. If might be enlightening to step back from the tendentious and

Re: A lurker surfaces

2007-01-02 Thread M. Warner Losh
In message: [EMAIL PROTECTED] Daniel R. Tobias [EMAIL PROTECTED] writes: : On 2 Jan 2007 at 11:56, Ashley Yakeley wrote: : : GPS is TAI. I'm not proposing abandoning TAI for those applications : that need it. : : It's a few seconds off from TAI, isn't it? It was synchronized to :

Re: A lurker surfaces

2007-01-02 Thread Magnus Danielson
From: Rob Seaman [EMAIL PROTECTED] Subject: Re: [LEAPSECS] A lurker surfaces Date: Tue, 2 Jan 2007 20:45:14 -0700 Message-ID: [EMAIL PROTECTED] Rob, Magnus Danielson wrote: If you do want a new timescale, I think rubber seconds isn't going to be the solution. One might point out

Re: A lurker surfaces

2007-01-02 Thread Magnus Danielson
From: Steve Allen [EMAIL PROTECTED] Subject: Re: [LEAPSECS] A lurker surfaces Date: Tue, 2 Jan 2007 21:35:24 -0800 Message-ID: [EMAIL PROTECTED] On Tue 2007-01-02T22:16:19 -0700, M. Warner Losh hath writ: changed in later revisions to be the same as GPS time. There's an extreme reluctance

Re: A lurker surfaces

2007-01-01 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Steve Allen writes: On Sun 2006-12-31T07:59:35 +, Poul-Henning Kamp hath writ: Rob, If you feel uncomfortable with calling leapseconds discontinuities, then we can use the term arrhythmia instead. The point of my allegory about unplanned pregnancies is that all

Re: A lurker surfaces

2007-01-01 Thread Ashley Yakeley
On Dec 30, 2006, at 17:41, Jim Palfreyman wrote: The earlier concept of rubber seconds gives me the creeps and I'm glad I wasn't old enough to know about it then! I rather like the idea, though perhaps not quite the same kind of rubber as was used. I'd like to see an elastic civil second to

Re: A lurker surfaces

2007-01-01 Thread M. Warner Losh
In message: [EMAIL PROTECTED] Ashley Yakeley [EMAIL PROTECTED] writes: : Software should serve human needs, not the other : way around. Anyone needing fixed seconds should use TAI. I think this idea would be harder to implement than the current leapseconds. There are many systems

Re: A lurker surfaces

2007-01-01 Thread Michael Sokolov
Ashley Yakeley [EMAIL PROTECTED] wrote: I'd like to see an elastic civil second to which SI nanoseconds are added or removed. Ditto! I have always been in favor of rubber seconds, and specifically civil second. I believe that the *CIVIL* second should have its own definition completely and

Re: A lurker surfaces

2007-01-01 Thread John Cowan
Michael Sokolov scripsit: The people who complain about leap seconds screwing up their interval time computations are usually told to use TAI. They retort that they need interval time *between civil timestamps*. To me that seems like what they are really measuring as interval time is not

Re: A lurker surfaces

2007-01-01 Thread Ashley Yakeley
On Jan 1, 2007, at 17:03, John Cowan wrote: Michael Sokolov scripsit: The people who complain about leap seconds screwing up their interval time computations are usually told to use TAI. They retort that they need interval time *between civil timestamps*. To me that seems like what they are

Re: A lurker surfaces

2007-01-01 Thread M. Warner Losh
In message: [EMAIL PROTECTED] [EMAIL PROTECTED] (Michael Sokolov) writes: : The people who complain about leap seconds screwing up their interval : time computations are usually told to use TAI. They retort that they : need interval time *between civil timestamps*. Actaully, interval

Re: A lurker surfaces

2007-01-01 Thread Magnus Danielson
From: Michael Sokolov [EMAIL PROTECTED] Subject: Re: [LEAPSECS] A lurker surfaces Date: Mon, 1 Jan 2007 22:22:23 GMT Message-ID: [EMAIL PROTECTED] Ashley Yakeley [EMAIL PROTECTED] wrote: I'd like to see an elastic civil second to which SI nanoseconds are added or removed. Ditto! I have

Re: A lurker surfaces

2007-01-01 Thread John Cowan
Ashley Yakeley scripsit: Rubber seconds are appropriate because we have rubber days. People who need absolute time have their own timescale based on some absolute unit (the SI second), but to everyone else, the second is a fraction of the day. Well, okay. Does the rubberiness go down all

Re: A lurker surfaces

2007-01-01 Thread Steve Allen
On Tue 2007-01-02T01:48:26 -0500, John Cowan hath writ: Well, okay. Does the rubberiness go down all the way? Is a civil nanosecond one-billionth of a civil second, then? If so, how do we build clocks that measure these intervals? Let's not. Let's continue the valid and agreeable notion of

Re: A lurker surfaces

2006-12-31 Thread Ed Davies
Poul-Henning Kamp wrote: In message [EMAIL PROTECTED], Rob Seaman writes: Jim Palfreyman wrote: Just a reminder that UTC has no - none - nada - discontinuities. Various computer mis-implementations may, but the standard is very carefully constructed to avoid spring-forward or fall-back gaps

Re: A lurker surfaces

2006-12-31 Thread Steve Allen
On Sun 2006-12-31T07:59:35 +, Poul-Henning Kamp hath writ: Rob, If you feel uncomfortable with calling leapseconds discontinuities, then we can use the term arrhythmia instead. The point of my allegory about unplanned pregnancies is that all practically available time scales have

Re: A lurker surfaces

2006-12-31 Thread Tony Finch
On Sun, 31 Dec 2006, John Cowan wrote: However, it's clear that UTC does not contain the sort of jumps that LCT does, where a single broken-down time may represent two different UTC seconds. Not if you include the timezone offset in the representation. Tony. -- f.a.n.finch [EMAIL PROTECTED]

Re: A lurker surfaces

2006-12-31 Thread Zefram
Rob Seaman wrote: Just a reminder that UTC has no - none - nada - discontinuities. I concur, and so I prefer to say that UTC has _irregularities_. The rest of what Jim Palfreyman said applies to these irregularities: they must occur frequently so that the method of handling them is implemented

Re: A lurker surfaces

2006-12-31 Thread M. Warner Losh
In message: [EMAIL PROTECTED] John Cowan [EMAIL PROTECTED] writes: : Tony Finch scripsit: : On Sun, 31 Dec 2006, John Cowan wrote: : : However, it's clear that UTC does not contain the sort of jumps : that LCT does, where a single broken-down time may represent : two different

Re: A lurker surfaces

2006-12-31 Thread Rob Seaman
Poul-Henning Kamp wrote: Rob, If you feel uncomfortable with calling leapseconds discontinuities, then we can use the term arrhythmia instead. Which raises the question of why projects requiring an interval time scale lacking in such arrhythmias would have selected UTC in the first place.

Re: A lurker surfaces

2006-12-31 Thread M. Warner Losh
In message: [EMAIL PROTECTED] Rob Seaman [EMAIL PROTECTED] writes: : Poul-Henning Kamp wrote: : : Rob, If you feel uncomfortable with calling leapseconds : discontinuities, then we can use the term arrhythmia instead. : : Which raises the question of why projects requiring an

Re: A lurker surfaces

2006-12-30 Thread Rob Seaman
Jim Palfreyman wrote: With my time hat on, having time that is discontinuous pains me. It doesn't make sense in my heart. But at least these discontinuities are in whole seconds. Any discontinuities must be regularly done. So they are part of all computer systems and are tested and used all

Re: A lurker surfaces

2006-12-30 Thread M. Warner Losh
In message: [EMAIL PROTECTED] Rob Seaman [EMAIL PROTECTED] writes: : Just a reminder that UTC has no - none - nada - discontinuities. At the very least, the TAI-UTC difference is discontinuous with jumps at the leap seconds. One could easily suggest that 'UTC has discontinuities'