unruh <[email protected]> wrote: > On 2011-12-24, [email protected] <[email protected]> wrote: >> John Hasler <[email protected]> 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. > > But it is a few km inside the mountain. Is a mine in Denver not > underground just because Denver is 1600 m above sea level?
The issue is that most people don't seem to be able to understand how to get an accurate position of a location that is vertically under a km or so of dirt, yet horizontally feet from wide open sky and GPS signals. -- Jim Pennino Remove .spam.sux to reply. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
