I wasn't getting the right solution, so I did it over.  The GPS Formula is 
on the page,

http://mypeoplepc.com/members/jon8338/roots_to_polynomials_and_power_series/id2.html

with an example.

True, without the 4th satellite you can't ascertain if the location is in 
outer space or on the world, but probably a digital compass on the satellite 
would clear it up and require only 3 signals.


"junoexpress" <MTBrenneman@gmail.com> wrote in message 
news:1188775704.211183.308560@19g2000hsx.googlegroups.com...
> On Sep 2, 4:22 pm, "Jon G." <jon8...@peoplepc.com> 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.  This math is propounded at the web 
>> page,
>>
>> http://mypeoplepc.com/members/jon8338/roots_to_polynomials_and_power_...
>
> Problem is there is error associated with these three estimates due to
> the ionosphere effects, clock error, etc. For this reason, 4 position
> sources are almost always used for any reliable GPS receiver. In this
> case, either a least-squares solution or a Newton's method starting
> with what is known as a pseudo-range distance, is used.
>
> M
>