Le 11/08/2011 08:57, Attila Kinali a écrit :
On Wed, 10 Aug 2011 16:35:11 +0200
cook michael<[email protected]> 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 -2400000,5 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.
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