The system consists of three segments :-
- Space Segment
- Control Segment
- User Segment
This segment consists of 24 orbiting satellites in 6 different orbit paths at about 20000 km altitude.Each Satellite has an orbital period of about 12 hrs.At any time at least four satellites are above the user’s horizon at minimum elevation of 9.5 deg.
Following data is transmitted by each satellite over two frequencies
- Its Identity
- Its Position.
Extremely accurate Time of sending the message which is provided by the atomic clocks fitted on each of the satellites.
The control segment is composed of:
- A master control station (MCS),
- An alternate master control station,
- Four dedicated ground antennas,
- Six dedicated monitor stations.
- The user segment consists of the antenna and the receiver which is fitted on board a ship.
- There are multiplier supplier of these equipment, who pay license fees to USA for use of positional information broadcast by the GPS satellites.