Global Navigation Satellite Systems (GNSS)

It is a real time, all weather, 24hr, worldwide, 3 dimensional positioning system.

4 or more satellites are required. This is so a latitude, longitude, height, & time-based error can be obtained to provide a position as accurately as possible.

are precise microwave signals of transmitted data waves from space vehicles.

Satellite Errors- Clock error, Orbit error

Atmospheric Error- Ionospheric error, Tropospheric error

Receiver Error- Clock error, Station co-ordinate error