Re: [time-nuts] Why not TAI? (was: The future of UTC)
On Thu, 11 Aug 2011 09:20:04 -0700 "Tom Van Baak" wrote: > What is missed in many discussions about time scales is intent > or implied accuracy. If I manually adjust my Pacific Daylight > Time wrist-watch ahead by 7 hours does it then become a UTC > watch? If I further adjust it by 0.3 seconds can I now claim it's > showing UT1? Can I even wear a wrist-watch that displays TAI? > Is it possible for any clock with analog hands to display UTC? This is IMHO an orthogonal issue to choosing the "right" time scale. Yes, if a time scale is defined by using another time scale, then accurate tracking and its uncertainty becomes an issue that needs to be properly defined. But same goes to any measurment equipment where (absolute) time is meausred. If i capture events that occur randomly and i want to timestamp them, i have to somehow get a time source that fullfills my requiremtns of accuracy and precision. For the most common events that occur at "random" times (like "lunch with Bill") a time scale called "wrist watch" is good enough. Whether it is defined using TAI, UTC or anything else is of secondary importance, as long as it within a small confidence interval with regard to another time scale called "Bill's wrist watch" Same goes for any time scale used by scientific or technical installations where we measure events or time. Yes, we define the time scale relative to an existing one (most probably trackable to TAI), but it is not so important whether it fullfills the accuracy requirements of the application. > What we call a time scale is more than just an integer offset. I'm > working on a paper that explores all these issues. I'd like to read that. I hope you'll announce it on this mailinglist when you are finished? Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI? (was: The future of UTC)
On Thu, Aug 11, 2011 at 03:03, Mike S wrote: > > And who, exactly, says "don't use TAI?" Is this documented somewhere, or do > you have to be a member of the secret time society which wants to control it > all? For starters, we[1] are not called the "Secret Time Society". That would be a dead giveaway, wouldn't it? [1] I am not sure of the "we" part, as I have not met or even heard of any other members, but that is probably because we are super-secret. -- Sanjeev Gupta +65 98551208 http://www.linkedin.com/in/ghane ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI? (was: The future of UTC)
On 11/08/11 18:20, Tom Van Baak wrote: My Dual Scale Timekeeper will recover TAI from GPS by adding a constant 19 s offset, and it will track and serve out TAI in addition to UTR. What is usually meant by "TAI" is the single extremely accurate, post-processed, paper time-scale managed by BIPM. TAI itself is derived from EAL and other inputs. TAI is the basis of UTC. No one has copyright on these acronyms and confusion can result when TAI is used to mean too many things. You can "recover TAI" from a GPS timing receiver by adding 19 seconds in the same crude way I can recover TAI by looking at the big clock outside the bank building and adding 7 hours and 34 seconds. Or by taking a PC clock and making my web page: http://leapsecond.com/java/gpsclock.htm. Yes, these look like TAI. But are they really TAI? Or are they all just another 6-digit hour:minutes:second clock display that tries to be "close to" what TAI would look like if one had access to it? A question to ask is how many nanoseconds, or milliseconds, or even seconds does your TAI clock have to be off before you can't rightfully call it TAI anymore? I don't have an answer. Naming ambiguity is even worse with UTC. You can't have a clock at home that is UTC. What you can have at home is a WWVB clock that closely follows UTC(NIST) or a GPS display clock that closely follows UTC(USNO). But how close is left undefined. If you put the GPS receiver in holdover mode, when does the display stop being UTC? Most Windows PC's at home are off by seconds. Does that mean most of them are running UT1 instead of UTC? What is missed in many discussions about time scales is intent or implied accuracy. If I manually adjust my Pacific Daylight Time wrist-watch ahead by 7 hours does it then become a UTC watch? If I further adjust it by 0.3 seconds can I now claim it's showing UT1? Can I even wear a wrist-watch that displays TAI? Is it possible for any clock with analog hands to display UTC? What we call a time scale is more than just an integer offset. I'm working on a paper that explores all these issues. How close you need to get depends on your application and it's needs. If you need to be within +/- 1 us, then turning off your outputs when you expect to have drifted away 1 us from where the time-scale should be is resonable, this is a confidence interval thing. Whichever time-scale you try to realize, you will have biases, deviations and additional noise uncertainty. How much you tolerate and the requirement on hold-over depends on your application. It should not be very surprising. The concept of hold-over seems to be not as well covered in the literature as you would expect. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI? (was: The future of UTC)
My Dual Scale Timekeeper will recover TAI from GPS by adding a constant 19 s offset, and it will track and serve out TAI in addition to UTR. What is usually meant by "TAI" is the single extremely accurate, post-processed, paper time-scale managed by BIPM. TAI itself is derived from EAL and other inputs. TAI is the basis of UTC. No one has copyright on these acronyms and confusion can result when TAI is used to mean too many things. You can "recover TAI" from a GPS timing receiver by adding 19 seconds in the same crude way I can recover TAI by looking at the big clock outside the bank building and adding 7 hours and 34 seconds. Or by taking a PC clock and making my web page: http://leapsecond.com/java/gpsclock.htm. Yes, these look like TAI. But are they really TAI? Or are they all just another 6-digit hour:minutes:second clock display that tries to be "close to" what TAI would look like if one had access to it? A question to ask is how many nanoseconds, or milliseconds, or even seconds does your TAI clock have to be off before you can't rightfully call it TAI anymore? I don't have an answer. Naming ambiguity is even worse with UTC. You can't have a clock at home that is UTC. What you can have at home is a WWVB clock that closely follows UTC(NIST) or a GPS display clock that closely follows UTC(USNO). But how close is left undefined. If you put the GPS receiver in holdover mode, when does the display stop being UTC? Most Windows PC's at home are off by seconds. Does that mean most of them are running UT1 instead of UTC? What is missed in many discussions about time scales is intent or implied accuracy. If I manually adjust my Pacific Daylight Time wrist-watch ahead by 7 hours does it then become a UTC watch? If I further adjust it by 0.3 seconds can I now claim it's showing UT1? Can I even wear a wrist-watch that displays TAI? Is it possible for any clock with analog hands to display UTC? What we call a time scale is more than just an integer offset. I'm working on a paper that explores all these issues. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Le 11/08/2011 16:25, Jose Camara a écrit : The clock animations at http://www.leapsecond.com/java/gpsclock.htm are great, but one has to pay attention to the note at top, saying they are all based on your PC's clock, not actual time. If your pc is off 5 seconds, so will be all of those clocks. Yes indeed. It was on looking at them yesterday that I discovered that my PC clock was 7 sec adrift. I had not restarted ntp after maintenance some weeks back and :( ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
The clock animations at http://www.leapsecond.com/java/gpsclock.htm are great, but one has to pay attention to the note at top, saying they are all based on your PC's clock, not actual time. If your pc is off 5 seconds, so will be all of those clocks. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of mike cook Sent: Thursday, August 11, 2011 1:02 AM To: time-nuts@febo.com Subject: Re: [time-nuts] Why not TAI? > MJD , Modified Julien Date is the above -240,5 to keep the numbers > down. This was recognised as a time scale by the IUT. I think it is > now deprecated but is in common use. > > There are probably others. > Oops, typo.. It should be UIT or ITU and not IUT and I forgot the cavet. In general any exotic scale would have to be either created from scratch or calculated from the available TAI based scales as none are transmitted. Many web pages of course will give nice clock animations. I recommend tvb's. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
MJD , Modified Julien Date is the above -240,5 to keep the numbers down. This was recognised as a time scale by the IUT. I think it is now deprecated but is in common use. There are probably others. Oops, typo.. It should be UIT or ITU and not IUT and I forgot the cavet. In general any exotic scale would have to be either created from scratch or calculated from the available TAI based scales as none are transmitted. Many web pages of course will give nice clock animations. I recommend tvb's. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Le 11/08/2011 08:57, Attila Kinali a écrit : On Wed, 10 Aug 2011 16:35:11 +0200 cook michael wrote: If TAI is a paper clock, what else should be used if a strictly monotone time scale is needed? Do you have any specific application in mind? If you need an SI seconds rated scale, then you need something based on TAI. GPS time has a TAI second rate and is monotonic. But of course you would need a GPS receiver to access it. I don't have a specific application in mind. Just a general question on what should be used. But lets say i want to have a monotonic clock for a computer system to timestamp events precisely and unambigously. Yes, using GPS time (with or without going back to TAI) would be a probable solution. Are there any other time scales available that would fit that need? Attila Kinali Well, there is : TT, Terrestrial Time, which is uniform (interval SI second), monotonic ; with an epoc of 00h 00m 00s 1 Jan 1977 TAI with a constant offset such that [TT] = [TAI] - 32.184s . Or more exotic: ET, Ephemeris Time, which is uniform and monotonic with a non SI second of 1/31566925,9747 of the tropical year of 1900. Julien Date is another , using SI second, but a numeric day label with an epoc of initial epoc defined as (UT) at midday on Monday Jan 1 4713 BC in the Julian calendar. It is measured in days and fractions with precision of about a millisecond and being numeric is so is easy to do calculations on. MJD , Modified Julien Date is the above -240,5 to keep the numbers down. This was recognised as a time scale by the IUT. I think it is now deprecated but is in common use. There are probably others. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
On Wed, 10 Aug 2011 16:35:11 +0200 cook michael wrote: > > If TAI is a paper clock, what else should be used if a strictly monotone > > time scale is needed? > Do you have any specific application in mind? > If you need an SI seconds rated scale, then you need something based on > TAI. GPS time has a TAI second rate and is monotonic. But of course you > would need a GPS receiver to access it. I don't have a specific application in mind. Just a general question on what should be used. But lets say i want to have a monotonic clock for a computer system to timestamp events precisely and unambigously. Yes, using GPS time (with or without going back to TAI) would be a probable solution. Are there any other time scales available that would fit that need? Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI? (was: The future of UTC)
On 10/08/11 21:03, Mike S wrote: At 02:42 PM 8/10/2011, Magnus Danielson wrote... Much of todays "proliferation of UTC" or whatever it is being called, is due to the need of a TAI-like scale in a number of systems due to technical reasons. The time-lords could have avoided that from the start by acknowledging that use of TAI would be as valid as the use of UTC, where UTC is better suited as "legal time" basis while TAI is better suited for internal time in systems. They now tries to bend UTC itself into a UTC or TAI derivate. If they don't want people to use TAI for the TAI-like timescale, then use GPS or SMPTE, or LORAN, which are the same, only different. Taking the one widely distributed timescale which is earth rotation based and removing that characteristic is lunacy, especially when there are so many other suitable choices. You didn't get the tongue-in-cheek joke, now did you? I simply created another name for TAI. GPS time would be a good candidate for many uses. And who, exactly, says "don't use TAI?" Is this documented somewhere, or do you have to be a member of the secret time society which wants to control it all? Obviously there is some group of people having the idea that they rule this part of the world, for whatever reasons they see fit they seem to say "Don't use TAI" without caring for the needs, and then complain about GPS having it's own TAI-derivate for instance. Strange. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
At 02:40 PM 8/10/2011, Brooke Clarke wrote... There's been talk of a 19 second offset, but it may be 34 seconds, see: http://hpiers.obspm.fr/eoppc/bul/bulc/UTC-TAI.history The mention of "19 seconds" was in relation to GPS time, which is probably the most widely used source, from which others are obtained via offset. GPS - UTC = 15 TAI - GPS = 19 TAI - UTC = 34 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI? (was: The future of UTC)
At 02:42 PM 8/10/2011, Magnus Danielson wrote... Much of todays "proliferation of UTC" or whatever it is being called, is due to the need of a TAI-like scale in a number of systems due to technical reasons. The time-lords could have avoided that from the start by acknowledging that use of TAI would be as valid as the use of UTC, where UTC is better suited as "legal time" basis while TAI is better suited for internal time in systems. They now tries to bend UTC itself into a UTC or TAI derivate. If they don't want people to use TAI for the TAI-like timescale, then use GPS or SMPTE, or LORAN, which are the same, only different. Taking the one widely distributed timescale which is earth rotation based and removing that characteristic is lunacy, especially when there are so many other suitable choices. And who, exactly, says "don't use TAI?" Is this documented somewhere, or do you have to be a member of the secret time society which wants to control it all? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI? (was: The future of UTC)
On 10/08/11 20:24, Michael Sokolov wrote: Poul-Henning Kamp wrote: That is a very good question, the answers you get if you try to press this point starts with handwaving and ends with "look, just don't, OK ?" And what happens if you ignore their edicts and do it anyway? It's called Civil Disobedience. Using TAI is just like refusing to give up your seat on a segregated bus. Follow the example of Rosa Parks. My Dual Scale Timekeeper will recover TAI from GPS by adding a constant 19 s offset, and it will track and serve out TAI in addition to UTR. Naturally, we all use Universal Atomic Time (UAT) defined to be UTC with subtracted leap seconds. That it just happends to align up with TAI is an accident we don't bother to inform the time-lords about. Much of todays "proliferation of UTC" or whatever it is being called, is due to the need of a TAI-like scale in a number of systems due to technical reasons. The time-lords could have avoided that from the start by acknowledging that use of TAI would be as valid as the use of UTC, where UTC is better suited as "legal time" basis while TAI is better suited for internal time in systems. They now tries to bend UTC itself into a UTC or TAI derivate. Cheersm Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Hi: There's been talk of a 19 second offset, but it may be 34 seconds, see: http://hpiers.obspm.fr/eoppc/bul/bulc/UTC-TAI.history Have Fun, Brooke Clarke http://www.PRC68.com http://www.End2PartyGovernment.com/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI? (was: The future of UTC)
Poul-Henning Kamp wrote: > That is a very good question, the answers you get if you try to press > this point starts with handwaving and ends with "look, just don't, OK ?" And what happens if you ignore their edicts and do it anyway? It's called Civil Disobedience. Using TAI is just like refusing to give up your seat on a segregated bus. Follow the example of Rosa Parks. My Dual Scale Timekeeper will recover TAI from GPS by adding a constant 19 s offset, and it will track and serve out TAI in addition to UTR. MS ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Hi: A friend has an observatory and needs very precise time. It turns out that the best way is to command the system to point to some star then manually move the scope to put the star on the cross hairs. Doing this a half dozen times and then fitting the data results in the system knowing the time to maybe a millisecond. Doing an NTP sync or having a fancy time base in the control computer can only get within hundreds of a second. Remember that all the broadcast time signals are to the nearest second but WWV and WWVB send the tenths of a second offset for astronomical time but using that he could get to the nearest tenth of a second. But the above procedure gets him to maybe a millisecond. I say "maybe" because how well the scope points in terms of arc seconds of angle depends on many factors. So, maybe if you really want precision time you also need a very good observatory? Have Fun, Brooke Clarke http://www.PRC68.com http://www.End2PartyGovernment.com/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Hi If you have a time source to work with, generating a different time scale is just a math problem. In most cases it's not a very complex one (subtract 19 seconds and move on). If you don't have a time source, then generating any time scale will be a challenge. Given the low cost of computing gizmos these days, doing the math to come up with what ever you want is not going to be all that hard or expensive. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of cook michael Sent: Wednesday, August 10, 2011 10:35 AM To: time-nuts@febo.com Subject: Re: [time-nuts] Why not TAI? Le 10/08/2011 12:55, Attila Kinali a écrit : > > If TAI is a paper clock, what else should be used if a strictly monotone > time scale is needed? Do you have any specific application in mind? If you need an SI seconds rated scale, then you need something based on TAI. GPS time has a TAI second rate and is monotonic. But of course you would need a GPS receiver to access it. > And what makes UTC different from TAI to be a "real clock", as UTC is > derived from TAI by adding leap seconds? I don't think TAI is any less real than UTC. UTC just happens to be the international transmitted time scale. TAI is not generally available, though both GPS time, and UTC have the same rate. > Would a reverse definition of TAI (or rather TAI' ) by using UTC without the > leap seconds be a good enough approximation? Well, UTC doesn't exist without leap seconds by definition, but if you only have UTC available to be able to track TAI , then you can recover the TAI scale by deducting leap seconds. > I'm quite sure i'm not the first one asking this question, but i couldn't > find an answer, neither with google nor in the time-nuts archives. > > Attila Kinali ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Le 10/08/2011 12:55, Attila Kinali a écrit : If TAI is a paper clock, what else should be used if a strictly monotone time scale is needed? Do you have any specific application in mind? If you need an SI seconds rated scale, then you need something based on TAI. GPS time has a TAI second rate and is monotonic. But of course you would need a GPS receiver to access it. And what makes UTC different from TAI to be a "real clock", as UTC is derived from TAI by adding leap seconds? I don't think TAI is any less real than UTC. UTC just happens to be the international transmitted time scale. TAI is not generally available, though both GPS time, and UTC have the same rate. Would a reverse definition of TAI (or rather TAI' ) by using UTC without the leap seconds be a good enough approximation? Well, UTC doesn't exist without leap seconds by definition, but if you only have UTC available to be able to track TAI , then you can recover the TAI scale by deducting leap seconds. I'm quite sure i'm not the first one asking this question, but i couldn't find an answer, neither with google nor in the time-nuts archives. Attila Kinali ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
On Wed, 10 Aug 2011 19:16:33 +1200 Bruce Griffiths wrote: > > 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. > Strictly TAI, as presently realised, is a paper clock that isn't > actually available in real time. If TAI is a paper clock, what else should be used if a strictly monotone time scale is needed? And what makes UTC different from TAI to be a "real clock", as UTC is derived from TAI by adding leap seconds? Would a reverse definition of TAI (or rather TAI' ) by using UTC without the leap seconds be a good enough approximation? I'm quite sure i'm not the first one asking this question, but i couldn't find an answer, neither with google nor in the time-nuts archives. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
In message <4e425909.7050...@xtra.co.nz>, Bruce Griffiths writes: >These "local'' versions of TAI -TAI(NPL), TAI(NIST) etc, are also paper >ensemble averages and only a coarse approximation of them is available >in real time. This argument is pretty vacuous: UTC is also a paper clock, and the real time approximations of it, UTC(NPL), UTC(NIST) etc, are exactly as good or bad as their TAI parallels. In fact, they are by *definition* exactly as good or bad, because UTC is defined as an integral number of seconds offset from TAI. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Magnus Danielson wrote: On 10/08/11 09:16, Bruce Griffiths wrote: Attila Kinali wrote: On Fri, 15 Jul 2011 05:57:45 + "Poul-Henning Kamp" 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 Strictly TAI, as presently realised, is a paper clock that isn't actually available in real time. This is not entierly true. There are a few national laboratories which has a local representation of TAI, alongside their UTC. It is handy to say that TAI is a paper clock, but it is a comparable scale. Cheers, Magnus These "local'' versions of TAI -TAI(NPL), TAI(NIST) etc, are also paper ensemble averages and only a coarse approximation of them is available in real time. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
On 10/08/11 09:16, Bruce Griffiths wrote: Attila Kinali wrote: On Fri, 15 Jul 2011 05:57:45 + "Poul-Henning Kamp" 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 Strictly TAI, as presently realised, is a paper clock that isn't actually available in real time. This is not entierly true. There are a few national laboratories which has a local representation of TAI, alongside their UTC. It is handy to say that TAI is a paper clock, but it is a comparable scale. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
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 + "Poul-Henning Kamp" 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 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI? (was: The future of UTC)
In message <20110810074152.496cb081.att...@kinali.ch>, Attila Kinali writes: >On Fri, 15 Jul 2011 05:57:45 + >"Poul-Henning Kamp" 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? That is a very good question, the answers you get if you try to press this point starts with handwaving and ends with "look, just don't, OK ?" There are certainly no technical issues, so I suspect a major part of the "ban" is simply som that the metrology community do not want external constraints on TAI, so that they can change it to suit their needs without political paperwork. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Le 10/08/2011 07:41, Attila Kinali a écrit : On Fri, 15 Jul 2011 05:57:45 + "Poul-Henning Kamp" 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. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Attila Kinali wrote: On Fri, 15 Jul 2011 05:57:45 + "Poul-Henning Kamp" 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 Strictly TAI, as presently realised, is a paper clock that isn't actually available in real time. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
