[ntp:questions] Accuracy of NTP - Advice Needed

jimp at specsol.spam.sux.com jimp at specsol.spam.sux.com
Sat Dec 24 20:04:13 UTC 2011


John Hasler <jhasler at newsguy.com> wrote:
> unruh writes:
>> They require ns accuracy in the timing and m accuracy in the
>> distance. And the timing is not simply gps ( although they could have
>> gotten that wrong) but then that timing has to be brought down into
>> the mine a km or so below ground and horizontally and that also has to
>> be surveyed for the distance.
> 
> The NOvA detector is not in a mine so it should be possible to site the
> GPS receiver directly above it and drop a cable straight down.  The same
> should be possible at the Fermi end.  You could set up both timing
> chains at Fermilab (using indentical components including cable lengths
> if you want to be fanatical), calibrate them against each other for
> delay from antenna to output, and then pack one up and ship it up north
> (of course there may be good reasons not to do it this way).  The
> surveying should be easier than in Europe: there's no mountain range in
> the way.

That's the common misconception of the geology.

Basically the lab is in a tunnel in the side of a mountain and is no more
a km underground than is the lobby of a 20 story hotel 20 stories
underground.


-- 
Jim Pennino

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