The satellite navigation system consists of three segments:

• the space segment; at least 24 satellites in 6 orbit planes at an altitude of about 20 000 km . They broadcast continuously time, track and correction data to the user,
• the control segment;the master control station at Schriever Air Force Base (Colorado Springs) controls all transmitter and receiver stations (monitoring stations). Each monitoring station communicates information about satellite tracks, satellite clocks, transmission corrections and others to Schriever AFB,
• the user segment; GPS receiver with different accuracy and system stability. The position of the antenna is important. Undisturbed reception of the signal must be ensured.

The position accuracy of GPS is specified with ≤ 13 m. The USA reserves the right to decrease the accuracy without prior notice in regions where national interests of the USA are affected.
The accuracy of GPS position can be improved by using DGPS (Differential GPS).