Re: [PSUBS-MAILIST] UW-DGPS

[Phil Nuytten <72020.572@compuserve.com>]

Hi, Adam:
        Yeah, trisponder systems ( transponders on the sea floor) were used
years ago( and still are, for specific applications- usually precision
surveying) and are very accurate but bulky and a pain in the ass to move
all the time. Trackers and horizontal positioning systems use an ultra
short baseline - that is, you are actually triangulating - same as has been
done optically for the last few hundred years, but the third leg of the
triangle is in the surface unit, only a few inches from the second leg -
which is in the same box - the sub beacon is the other leg. Obviously,
having two legs, say, a thousand feet and one leg 12 inches, calls for an
accuracy of reading that is only possible with elctronics - even though it
is theoretically possible with optics, acoustics, etc.
Phil Nuytten