>>3 satellites would be enough Global positioning system(s)
assume an 'earth centered, earth fixed, x-y-z 3D cartesian
coordinate system'. Any location in this 3D space requires no
more than 3 components to be completely identified. So, even
though 3 spheres we obtain by 3 distance measurements intersect
at two different points, one of those points is rendered useless
by [ earth centered + earth fixed ] characteristic of the
coordinate system GPS assumes; we are interested in locations
below the earth's atmosphere. 3 satellites could be used to
determine 3 position dimensions with a 'perfect' receiver clock
(with an expensive atomic/optical clock). !YES!, you !could have
gotten! a 3D position fix with 3 satellites IFF the GPS receiver
you are using was equipped with an atomic clock. (The
ELIMINATION of the second point, on the bottom left figure of
the illustration above, is done "intuitively" as it corresponds
to someplace in DEEP SPACE. BECAUSE, there is a reason why GPS
satellites are at their specific con