Re: Precision vs. resolution

[Tom Van Baak]

> Can someone lay out for me exactly what the difference is between
> clock precision and clock resolution?  I've read the NTP FAQ and
> several other pages but am more confused than ever.
>
> (I do understand the distinction between precision and accuracy:
> 3.1429493 is \pi precise to 8 significant digits, but accurate
> only to 3.)

Key words for clocks and clock measurement include:
precision, accuracy, stability, resolution, and granularity.

Here's an informal stab at definitions for you:
  Accuracy is how close a clock is to an accepted standard.
  Precision relates to how consistent measurements are.
  Stability refers to how well a clock keeps time over time.
  Resolution is how precise one can measure.
  Granularity is the minimum [digital] increment of one reading to another.

/tvb
http://www.leapsecond.com/time-nuts.htm

Re: Precision vs. resolution

[Rob Seaman]

On May 24, 2006, at 7:25 AM, John Cowan wrote:


Can someone lay out for me exactly what the difference is between
clock precision and clock resolution?


Interesting question.  Perhaps it is the distinction between
addressability
and physical pixels that one encounters on image displays and hardcopy
devices?  (Still have to posit which is which in that case :-)

You might have more luck directing this question to time-nuts
(http://www.febo.com/pipermail/time-nuts) or perhaps the NTP WG
([EMAIL PROTECTED]) - although one would be delighted to find
this list capable of generating a knowledgeable response to any
such clearly expressed neutral question :-)

Rob
NOAO

Re: extracting leap second schedule

[Rob Seaman]

On May 24, 2006, at 6:27 AM, Zefram wrote:


I've written a Perl module that handles the conversion between TAI and
UTC.  It's Time::UTC, available at .
When asked about future times where it doesn't yet know the
leap second schedule, it automatically downloads and parses
.  This works well if
there's
a future leap second already scheduled, but otherwise there is a
problem
in working out how far ahead the last TAI-UTC offset applies.


Note that in a leap-secondless alternate reality, exactly the same
issues
would be encountered when trying to predict UT1 given TAI (or its
evil kirk
twin, "new-UTC").


Amusingly, in the long run this will become a non-problem on its own.
In perhaps a century or so it will become unavoidable to schedule
more than one leap second ahead.  That way the final time mentioned in
tai-utc.dat will always be in the future.


Non-amusingly, in the alternate no-time-of-day universe, this never
becomes a non-issue for recovering the orientation of Earth-2.

Rob Seaman
National Optical Astronomy Observatory