achsofromm wrote:

> Jon G. wrote:
>
>> The satellite signals its coordinates and time stamp to the receiver, which
>> is enough information to determine the distance from the satellite to the
>> receiver.  When this is done with 3 satellites, the location of the receiver
>> can be found with a little math.
>
>Seems like you could locate a point with only two satellites provided
>the satellites or a person could determine the satelites poisition
>relative to the other single satellite.

The two-satellite solution makes the assumption that the receiver is
on the surface of the Earth (and that said surface is on a sphere),
doesn't it?  GPS is widely used in aviation now, so it had better be
able to determine not only latitude and longitude but altitude.

(Besides, even with LORAN, which, if I remember correctly, did assume
that all of the receivers (as well as the transmitters) were not only
on the surface, but at "sea level", using two transmitters would still
leave two possible points - a third was needed to determine which of
the two is correct.)

-- Don