In message , Michael Williamson
writes
Cub Driver wrote:
How true is this, really? In an aircraft, you are between the
ground
and the satellite. How does someone on the ground interfere with the
signal?

I don't believe that the antenna for the GPS is directional enough
that someone off axis couldn't put a signal into your system- after
all, a single antenna is used to pick up every satellite above the
horizon.

It can be made directional, for a cost. It can even be persuaded to null
out jammers... for a cost.

Trouble is, jammers are cheap.

--
When you have to kill a man, it costs nothing to be polite.
W S Churchill

Paul J. Adam MainBoxatjrwlynch[dot]demon{dot}co(.)uk