Re: The GPS GR Correction, put to Rest.

From: Randy Poe (poespam-trap_at_yahoo.com)
Date: 09/27/04 

Date: 27 Sep 2004 12:09:17 -0700

"Myxococcus xanthus" <mold-guardian_NO_SPAM@comcast.net> wrote in message news:<9AR5d.119009$MQ5.97545@attbi_s52>...
> "Henri Wilson" <H@..> wrote in message
> news:2p6fl099hgnmguugh9gn65neh5lj9g7gvq@4ax.com...
> > You haven't a clue, Myxo!
>
> Those are LEAP SECONDS, kid. GPS time is nominally held to within
> 1 microsecond of an exact LEAP SECOND, and in practice has been held
> to within several dozen nanoseconds of an exact LEAP SECOND.
>
> LEAP SECONDS are added due to inaccuracies in the rotation of the Earth,
> NOT due to inaccuracies in GPS.
>

I've been meaning to waste on Henri a brief tutorial on
the difference between a rate adjustment and an offset.
This seems to be an opportune moment.

To Henri: Here's part 1. Imagine you have two clocks.

Each clock is checked at midnight every day.

Clock A reads 12:00:00 the first day, 12:10:00 the second
day, 12:20:00 the third day... 1:00:00 the 7th day, etc.

Clock B reads 12:13:01 the first day, 12:12:59 the second
day, 12:13:03 the third day... 12:13:00 the 7th day,
and every day it reads within 3 seconds of 12:13:00 when
checked.

(A fine point: I should mention that the checking procedure
includes monitoring both clocks for one minute, to be
sure they are running at nominally the correct rate).

Question: Which of these clocks is running at closest to
the correct rate?

         - Randy

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