triateration and mapping
correct me if I am wrong.
the satellites perform "triateration" (is the term used when using distances as against bearing when it is triangulation) to fix the position of the receiver in space.(distance from the center of the earth to be exact)this is only half the job because now we need to reference it to the surface of the earth or at a height above the surface of the earth.so it boils down to which earth model is used.At the moment WGS84 is the aviation standard.I am not sure if the handheld units use the same.