EGNOS is the first European Satellite Navigaton System which takes profit from GPS signal. The project started in 1995 but the system began to operate on October the 1st 2009. EGNOS is not a positioning satellite system ,like GPS, but an Augmentation one (it receives the signal from the positioning systems and then improves its accuracy). There exist different Satellite-Based Augmentation System (SBAS) such as WAAS in USA and MSAS in Japan and as we have said, EGNOS in Europe which was also designed following the SBAS standards. EGNOS provides a more precise positioning than GPS and it will be increased even more when GALILEO will be operative. The immediate applications of this system are: takings off, ships crossing narrow channels, tracking trains,… however, there exist lots more that we will mention and even others that wait to be discovered.
EGNOS consists in 3 telecommunications satellites positioned in a geostationary orbit, 36000km height. Thus all of them are always visible from Europe, Africa and the Middle East. EGNOS collect data from GPS satellites monitored by multiple Ranging & Integrity Monitoring Stations (RIMs). Four Mission Control Centers receive the data from the RIMs and do the respective corrections. Then the augmented signals are transmitted from the 6 Navigation Land Earth Stations to EGNOS satellites and later broadcast to users.
Within EGNOS we can distinguished 3 different services: Open Source (OS), Commercial Data Distribution Service (CDDS) and Safety of Life service (SoL). OS, it was the first to be operated, it provides an horizontal and vertical accuracy of 1-3m and 2-4m respectively, so improving the one from GPS. OS is being developed in agriculture (it reduces the use of fertilizers), to guide blind people via mobile phones, to secure and improve ground traffic flow, … Second, CDDS, destinated to professional users through controlled access which can be done by conventional networks as GSM and the Internet. The information provided by this service is: raw GPS data from the EGNOS ground segment and EGNOS message corrections and integrity in real time (GPS clock, ionosphere correction,…). Its applications remain for professional uses. Last, SoL, designed for the aviation community. Two service levels are distinguished within it: Non-Precision Approach (NPA) and Approach with Vertical guidance (APV). Some test applications have already been proved in landings with fewer aids or in helicopters emergency landings.
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