If ever you are strapped into an airplane and the plane glides silently through the air with no noise, you barely even notice there is an unseen but majestic guiding system mapping out step by step along the flight: GPS. Contemporary flight employs the Global Positioning System not just for navigation, but for safety, accurate landing, and international communication.
But how does it actually operate in aviation in the real world? Look at the amazing technology that is making flight more efficient and safer.
1. Brief Background: What is GPS?
GPS, Global Positioning System, is a satellite navigation system constructed by the United States Department of Defense in the 1970s. It is now provided to the masses of the world for free.
- The constellation is made up of some 31 operational satellites in orbit around the Earth.
- They broadcast radio signals to the planet at all times.
- A receiver for the GPS, on a plane for example, receives the signals and has a very accurate idea of where it is.
GPS totally transformed the aviation navigation system. Pilots were previously using ground radio beacons such as VOR (VHF Omnidirectional Range) and NDB (Non-Directional Beacon). Though still in use, they are being phased out in favor of satellite navigation.
2. How GPS Determines Position
GPS works on a principle that can be described as trilateration.
- All the satellites continuously send a message of its position and the time now.
- The plane's GPS receiver calculates how far away the signal has traveled.
- Radio signals travel at the speed of light, so it could be able to calculate it is at least four satellites away.
- By correlating a minimum of four satellites, the GPS receiver can calculate aircraft position in latitude, longitude, altitude, and time.
Short and simple:
- 3 satellites = 2D position (latitude & longitude)
- 4 satellites = 3D position (altitude included)
The result is a determinable, measurable position of the airplane anywhere on the planet, even in the middle of the ocean or desert where there's not even a ground station in existence to track.
3. Aviation GPS vs. Generic GPS
You might be wondering: how does aviation GPS differ from your car or cell phone GPS?
Same sat signals down here, anyway. But aircraft GPS is more powerful and smarter because:
- It is integrated in avionics hardware (autopilot, flight computer).
- It's applied to aviation-specific navigation such as RNAV (Area Navigation) and RNP (Required Navigation Performance).
- It must be rigorously certified on the global safety level
- It's typically used with augmentation systems to improve accuracy.
4. Augmentation Systems: Enhancing GPS Accuracy for Aviation
Street-level GPS is 10–15 meters accurate adequate for a car, yet at times too risky for planes that must line up with runways exactly.
Aviation fills GPS voids with augmentation systems:
- WAAS (Wide Area Augmentation System) – Used in the United States, enhances precision to 1–2 meters.
- EGNOS (European Geostationary Navigation Overlay Service) – In three EU member states.
- MSAS (Japan) and GAGAN (India) – Regional.
- GBAS (Ground-Based Augmentation System) – In airports, to offer precision approach similar to ILS (Instrument Landing System).
They provide not only greater precision but integrity i.e., GPS notifies pilots when the signal is uncertain. Integrity is totally essential in aviation.
5. Pilots' Application of GPS in the Cockpit
GPS is interfaced to the Flight Management System (FMS) and cockpit display. How it assists pilots is:
A. Navigation Enroute
- Pilots navigate by airway routes in disguise as waypoints (airborne virtual positions expressed in terms of latitude/longitude).
- GPS allows continuous tracking along such airways even over water.
B. Approaches and Landings
- GPS facilitates RNAV (GPS) approaches, where aircraft land safely at airports without the costly ground installation of ILS systems.
- With WAAS/GBAS augmentation, aircraft can conduct Category I precision approaches, gliding mere meters off the runway centerline.
C. Situational Awareness
- GPS displays accurate aircraft position on dynamic screens.
- Decreases navigation error and controlled flight into terrain (CFIT).
D. Performance Monitoring
- GPS offers groundspeed, track, and estimated time of arrival (ETA).
- Communications to autopilot for smoother ride.
6. Benefits of Aviation GPS
GPS has revolutionized aviation in nearly all ways:
- Global Coverage: Everywhere in the world, even above the ocean and polar regions.
- Less Ground Stations Needed: Low cost to insure thousands of navigation beacons.
- Fuel Conservation: Shortcut routes conserve fuel and reduce air pollution.
- Improved Safety: Crash procedures eliminate landing hazards.
- Greater Capacity: GPS enables more aircraft to operate economically in heavy airspace.
7. Constraints of GPS in Aviation
GPS is wonderful but not perfect. Some of its imperfections are:
- Signal Interference: GPS signals are low power and can be jammed or spoofed.
- Solar Storms: Space weather can interrupt satellite signals.
- Dependence: Complete reliance on GPS makes it vulnerable to catastrophe should the system be lost.
- Backup Systems Required: Pilots should resort to VOR, DME, and inertial navigation in case of GPS failure.
This is why air organizations like ICAO and FAA implement redundancy stress GPS is the main but not the only navigation.
8. GPS Use in Air Traffic Control
GPS is used exclusively by pilots. ATC also benefits from a system known as ADS-B (Automatic Dependent Surveillance – Broadcast).
- Use GPS in calculating their location for flight paths.
- Automatically transmit this location to ATC and surrounding aircraft.
- Is being used to make radar-free real-time locating possible.
ADS-B is also becoming a NextGen building block air traffic control function to enable safer, more efficient airspace.
9. A GPS Solution in a Real-Life Situation
Assuming that in one stormy night an airplane lands at the local airport. The airport does not have an ILS system because of economic considerations in the past.
With GPS, the aircraft can execute an RNAV (GPS) approach:
- The FMS executes the step-down altitudes approach procedure.
- GPS guides the aircraft along a pre-selected lateral and vertical path.
- There is a window of opportunity to descend to 200–250 feet above the airport on WAAS before visual acquisition for landing.
This allows small airports to safely accept new airliners previously unimaginable.
10. Future Aviation GPS
And, much more importantly, in the future
- Multi-constellation Navigation: Existing business airline flight operations already use not only GPS (U.S.) but also GLONASS (Russia), Galileo (EU), and BeiDou (China) as a backup.
- Enhanced GBAS: May enable Category III autoland with the use of GPS instead of traditional ILS.
- Artificial Intelligence Integration: GPS and artificial intelligence could navigate and predict turbulence.
- Air Taxis (Urban Air Mobility): GPS would be the driver for low-altitude high-density airspace navigation over future cities in a safe mode.
11. Conclusion: GPS – The Silent Guide of the Skies
GPS aviation isn't really a navigation system it is a twentieth-century airplane safety system. From guiding jets across the oceans to small aircraft into distant villages, GPS is delivering precision, economy, and global capability.
It accomplishes this by using the satellites, determining the range, and developing an accurate fix. Augmentation systems have improved, GPS now delivers accuracy required for new air operations.
Not perfect, I hope, and multi-constellation mode, but with constant evolution is that aviation GPS will simply continue to revolutionize the manner in which we fly.
The next time you look out of the window on cruising height, pay attention: it's not just the pilots who are taking you to your destination on schedule it's a sequence of satellites whirring in the background.