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Positioning Application: What is the European Geostationary Navigation Overlay Service (EGNOS)?
What is EGNOS?
EGNOS is the European, regional, satellite-based augmentation system (SBAS) that augments the US GPS satellite navigation system and makes it suitable for safety critical applications such as flying aircrafts or navigating ships through narrow channels.
Why is EGNOS important?
EGNOS and in general SBAS are important because the primary navigation satellite systems (GPS, GLONASS) were not designed to meet real-time integrity monitoring capabilities required by the civil aviation navigation safety needs. The main goals of EGNOS and SBAS are to provide integrity assurance and to increase the accuracy with position errors below 1 meter. EGNOS-augmented signals are guaranteed to meet the high performance standards set out by the International Civil Aviation Organization (ICAO).
How does EGNOS work?
EGNOS consists of 3 GEO satellites and a network of ground stations. This network of stations, located at accurately surveyed positions, determines the accuracy data of the satellite navigation systems and provides corrections to the original navigation information of the primary constellation (GPS). Next, it transmits all the corrections to the GEO satellites (using the C-band to upload the corrections) and then the EGNOS navigation message is disseminated over the service area by a GEO satellite (using the L-band for downlink) allowing users to determine their position to within 1.5 meters.
The future of EGNOS
EGNOS V3 will be the second generation of the EGNOS system (currently EGNOS V2) and is expected to be operational in 2020. It will provide Precise Point Positioning (PPP), or positioning at the centimeter to decimeter level and will deliver high accuracy positioning to a range of applications, such as agriculture, road, mapping/surveying, construction, offshore mining, maritime, etc. The official European Commission decision,
the Commission Implementing Decision of 17th of July 2015
, set out all the necessary technical and operational specifications for implementing version 3 of the EGNOS system. The main characteristics of EGNOS V3 will be:
Implementation of a second protected frequency (GPS L5) to offer to the dual-frequency SoL users a more robust and accurate vertical guidance service.
GALILEO constellation (E1/E5a) will be added so that a dual-frequency (GPS L1/L5 - GALILEO E1/E5a) dual-constellation (GPS / GALILEO) option becomes available to users.
CAT-I precision approach.
Specific services, such as navigation in harbor entrance, harbor approaches and coastal waters will become available.
Improvement of the overall robustness of EGNOS services against increasing security risks.
EGNOS V3 System Architecture
The system's architecture is similar to EGNOS V2. It consists of 3 segments:
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