unruh <[email protected]> wrote: > 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.
Where do you see the words "few feet" in what I wrote? The bottom line is that the only thing that is relevant is the path to the GPS antenna with a clear view of the sky. Everything else is bloviation. -- Jim Pennino Remove .spam.sux to reply. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
