Global Positioning System (GPS)
The Global Positioning System (GPS) is a US-operated satellite navigation system that provides accurate position, velocity, and time information to users worldwide. In aviation, GPS/GNSS (Global Navigation Satellite System) is the primary navigation sensor for area navigation (RNAV) operations, including en route navigation and instrument approaches.
How GPS Works
A GPS receiver simultaneously receives signals from at least four satellites and uses the measured time delays to calculate its three-dimensional position. With four or more satellites in view, the receiver can determine latitude, longitude, altitude, and time accurately. Modern aviation GPS receivers use WAAS (Wide Area Augmentation System) in North America to correct errors and provide the accuracy required for precision approaches.
GPS in Canadian Aviation
- RNAV (GNSS) approaches are published at thousands of Canadian aerodromes
- GPS is required for RNAV 5, RNAV 2, RNAV 1, and RNP operations
- WAAS-enabled GPS receivers (certified for LPV approaches) can provide DH as low as 200 ft
- ADS-B Out relies on GPS position data
- GPS is required equipment for Class A airspace operations
GPS Limitations
- Signal outage possible during solar storm events
- GPS jamming and spoofing are emerging threats
- Database currency must be verified before IFR use
- Always cross-check GPS with other available navigation sources