At 19:39 3/22/2000, BRENT CHRISTENSEN wrote:
>(I won't go into the specifics of this random deviation, but suffice it to
>say that it is a matter of national security...)  :-)

(I.e. we didn't want other people using our GPS system to fly cruise
missiles down our throats, inconveniencing passers-by and destroying
helpless Vanagons...)

Or at least it was, until Russia fielded its own GPS-equivalent -- you can
now buy ($$$) receivers that will work with both systems.

And of course our own Coast Guard, hoping to do away with the labor- and
plant-intensive LORAN-C system, has installed differential transmitters in
many coastal locations so that a properly equipped GPS can correct for
"Selective Availability."  Even so, the system has more jitter in it than
LORAN-C, which means the speed readouts are pretty flaky at low
speeds.  I've watched my brother-in-law's pilot-type unit on our boat going
about four knots, and the speed was anywhere from half a knot to ten,
according to the GPS.  The absolute accuracy of GPS is better than LORAN,
but the repeatability is not as good.

david

David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"