What is WAAS (wide area augmentation system)

WAAS: Wide Area Augmentation System

WAAS (Wide Area Augmentation System) is a satellite-based navigation system developed by the Federal Aviation Administration (FAA) to enhance the accuracy, integrity, and availability of the Global Positioning System (GPS). It's designed to provide precise positioning information for aviation, but it's also used in other applications.

How WAAS Works

1. Ground-Based Reference Stations (WRS): These stations are strategically located across the coverage area. They continuously monitor GPS satellite signals and detect any errors or discrepancies.
2. Master Stations: These stations collect data from the WRS and process it to generate correction messages.
3. Geostationary Satellites: The correction messages are transmitted to geostationary satellites.
4. User Equipment: GPS receivers equipped with WAAS capability receive the correction messages and apply them to the GPS signals, improving accuracy and integrity.

Opens in a new windowwww.faa.govWAAS system architecture

Key Components of WAAS

• Wide Area Reference Stations (WRS): Ground-based stations that monitor GPS signals.
• Master Stations: Process data from WRS and generate correction messages.
• Geostationary Satellites: Relay correction messages to users.
• User Equipment: GPS receivers with WAAS capability.

WAAS Performance

WAAS provides significant improvements over standard GPS:

• Accuracy: Horizontal accuracy of 7.5 meters (95% probability) and vertical accuracy of 5.7 meters (95% probability).
• Integrity: Provides information about the reliability of the GPS position, allowing users to detect and avoid erroneous information.
• Availability: Offers continuous service over the coverage area.

WAAS Benefits

• Enhanced Aviation Safety: Enables precise navigation, approach, and landing procedures.
• Improved Efficiency: Reduces reliance on ground-based navigation aids.
• Increased Accessibility: Provides navigation services in areas with limited ground-based infrastructure.

Challenges and Limitations

• Dependency on Ground Infrastructure: The system relies on a network of ground stations for accurate performance.
• Signal Propagation: Atmospheric conditions and ionospheric disturbances can affect signal propagation and accuracy.
• Coverage Limitations: WAAS is primarily designed for North America and has limited coverage in other regions.

WAAS and Other Augmentation Systems

WAAS is one of several satellite-based augmentation systems (SBAS) worldwide. Other notable systems include:

• EGNOS: European Geostationary Navigation Overlay Service
• MSAS: Multi-functional Satellite Augmentation System (Japan)
• GAGAN: GPS Aided Geo Augmented Navigation (India)

Conclusion

WAAS has revolutionized aviation navigation by providing highly accurate and reliable positioning information. Its success has led to the development of other SBAS systems worldwide, enhancing safety and efficiency in various applications beyond aviation.