>
> Yes, anyone can use the GPS (global positioning system) signals.  There
are
> some encrypted military channels that allow the military to correct for
> errors intentionally introduced to reduce the resolution of the system
for
> non-military uses.  Even the military channels provide resolution on the
> order of a meter.  A special application method can be used to get ~ 1 cm
> resolution but this requires a fixed reciever in a known location nearby
to
> decode its position from the GPS signals and, knowing where it is,
broadcast
> a correction factor(s) to nearby recievers.
>
> Mark A. Corio
> Rochester MicroSystems, Inc.
> 200 Buell Road, Suite 9
> Rochester, NY  14624
> Tel:  (716) 328-5850 --- Fax:  (716) 328-1144
> http://www.frontiernet.net/~rmi/
>
> ***** Designing Electronics For Research & Industry *****

It's called Differential GPS.
-It's expensive
-It's not real time
-It requires a lot of computation
-It requires specific knowledge of the ground station location

No GPS application would have the accuracy required.  Furthermore, GPS is
not real time (not to good for correcting a slide which need real time
feedback).


Gerald Morrison
Smart Technologies Inc.