Not for aircraft anymore Larry. Maybe it was at some point in the past, but certainly not now. Basically there are a series of
gyroscopes mounted on a common platform in 3 axis. These measure acceleration in pitch, roll and yaw. These are fed to a computer
system where these a computed with a very accurate time source to determined distance travelled. Effectively, these are very
accurate dead reckoning systems. Obviously, error accumulation over both time and distance is their weakness and from time to time
must be reset from another position source. Their big advantage is they need no radio signals to function, so they are stealthy.

Also Larry, you may be confusing GPS systems with satellite compasses. They do not work the same way. Satellite compasses work by
positioning 2 or more GPS receivers at fixed, accurately positioned distances from each other and the receivers then use only the
signal carriers and do phase comparison to determine the bearing of the centerline of the ship. No satellite intelligence is used
in the system. Therefore no motion is necessary. Bearing info from GPS systems in comparison is extrapolated track data.
Steve

"Larry" wrote in message ...
Bruce wrote in
:

How does the inertial navigation system, used on submarines, work? Or
are they outmoded?

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)


Sorry, that's classified.

--
Creationism is to science what storks are to obstetrics.

Larry