EGNOS is a regional satellite-based augmentation system that enhances GPS accuracy for surveying and navigation across Europe.
EGNOS: European Geostationary Navigation Overlay Service
Overview
ENGOS (European Geostationary Navigation Overlay Service) is a regional satellite-based augmentation system (SBAS) developed by the European Space Agency (ESA), the European Commission, and Eurocontrol. It enhances the accuracy, integrity, and availability of Global Positioning System (GPS) signals across Europe, North Africa, and the Middle East.
History and Development
ENGOS was initiated in the 1990s to improve upon the limitations of standalone GPS for critical applications. The system became operational in 2009 and has since been refined to support various surveying and positioning requirements. It represents Europe's commitment to providing independent navigation infrastructure.
Technical Components
The EGNOS system consists of three main components:
Space Segment: Three geostationary satellites (INMARSAT and ASTRA satellites) transmit correction data from fixed orbital positions above the equator.
Ground Segment: A network of reference stations across Europe monitors GPS satellite signals and calculates correction factors. These corrections are processed at control centers and uploaded to the geostationary satellites for broadcast.
User Segment: EGNOS receivers located in surveying equipment, vehicles, and devices receive both GPS signals and EGNOS correction messages to compute enhanced positions.
Accuracy Improvements
ENGOS provides significant improvements over standard GPS:
Standard GPS: Horizontal accuracy of 5-10 meters
EGNOS-enhanced GPS: Horizontal accuracy of 1-2 meters (in optimal conditions)
Vertical accuracy: Enhanced from 8-15 meters to 2-3 metersSurveying Applications
In surveying, EGNOS is particularly valuable for:
Real-time kinematic (RTK) positioning
Land surveying and mapping
Cadastral surveys
Infrastructure monitoring
Environmental assessments
Agricultural mapping and precision farmingCoverage Area
ENGOS provides coverage across:
Europe and the Mediterranean region
North Africa
The Middle East
Parts of sub-Saharan Africa
Signal availability extends to approximately 35°W to 45°E longitudeIntegrity and Reliability
One of EGNOS's key advantages is its emphasis on
integrity—the system quickly detects when GPS satellites malfunction and alerts users. This is critical for safety-of-life applications such as aviation.
Integration with Galileo
As Europe's independent Global Navigation Satellite System (GNSS), Galileo is designed to work seamlessly with EGNOS. Future developments include tighter integration between these systems to provide even more robust positioning solutions.
Advantages
Free access to correction signals
Regional focus optimized for European conditions
High integrity monitoring
Improved accuracy without expensive ground-based infrastructure
Operational 24/7 with high availabilityLimitations
Requires clear line of sight to geostationary satellites
Dependent on GPS constellation availability
Less accurate than differential GPS systems in some applications
Coverage limitations in far northern latitudesFuture Developments
ENGOS is continuously being modernized. Plans include integration with Galileo signals for enhanced performance and potential expansion to support higher accuracy requirements for emerging applications.
Conclusion
ENGOS represents a significant advancement in regional navigation augmentation, providing European surveyors and navigation professionals with cost-effective access to enhanced positioning accuracy and integrity monitoring capabilities essential for modern surveying applications.