: Pretty much. The system works by comparing signals sent from a number of
: (typically 3 or 4, sometimes more) satellites. The most important part of
: the signal is an accurate clock pulse. By comparing the relative
: "offness" of the clock signal between satellites (because the
: radio wave and therefor the clock signal) ONLY travels at the speed of
: light, the GPS can calculate your (and it's) location.

: Because this was initially for military purposes, they messed up the timing
: slightly. Military GPS units were designed to take the messed up timing
: into account, and they are able to compensate for it and display an
: accurate location. Civillian GPS's are unable to compensate for this, and
: therefore always displayed your location incorrectly. Close enough for
: most purposes, but not accurately. For example, you might be sitting
: dockside at sea level, but your GPS would insist that you were actually
: 100 feet above sea level...

: This "feature" has now been deactivated, so civillian units now
: display positions as accurately as the military ones.

: By the way, during the Gulf War, the jitter was removed, because there were
: not enough "military" GPS's to go around.

Thanks, Charles, quickest response i ever saw! Guess i'll have to run around the house just to see it work!

Totto