On 2011-12-24, [email protected] <[email protected]> wrote: > 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.
A few feet? I assume that was a misprint for a few km. > > > _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
