Re: GPS

> Currently civilian GPS is about the same accuracy as military GPS
(about
3m) but when SA (Selective Availability) was active the accuracy for
civilians was 100's of m to 1.5 km.  The military turned off SA a few
years
ago.

Garmin/GME would like you to think so - the average accuracy is about 5
m in
real life with a civilian unit - both precision and military units have
greater accuracy levels and even then the qualityu of the unit plays a
big
part.

> The military reserves the right to add SA whenever they wish as GPS is
a
military system which they happen to allow civilians to use.  As it is a
US
military system it makes our European Allies a bit nervous and they are
setting up their own GPS satellite network.

EGNOS - European Geostationary Navigation Overlay Service - it will not
replace GPS, just augment the existing service for civilian and
precision
units and then help in the event of the return of SA. The US already has
a
similar system called WAAS.  (EGNOS should be operational by the end of
2003).

> Differential GPS depends on known land sites to send out GPS signals -
effectively becoming another GPS satellite, however they are limited by
radio range to be effective.  Such locations would be known or easily
discovered and could be knocked out in a war, since they have to
transmit to
be effective.

HARMS will do the job nicely.

Brendan