Global Positioning System - Obtaining GPS Data is the actual
process of finding your geographic position on earth. Following
planning, the user is ready to collect data in the field. As
stated previously, the rover unit needs at least four satellites
to determine position. If elevation is known, three satellites
are sufficient, but the user must define that elevation in the
rover unit. The position of the rover unit is where the vectors
between the rover unit and the satellites connect. Hence, one,
two, or three satellites leave too many possibilities for the
position of the rover unit. With four satellites, the vectors
can only intersect at one geographic position, that being the
position of the rover Pseudo Random Code Figure 3: Pseudo Random
Code Because the satellites are moving in outer space and the
rover unit is moving with the rotation of the Earth, your
position is calculated by what must be two stationary points in
space. Obviously, the rover unit and the satellites are not
stationary. How is the po