European Geostationary Navigation Overlay Service
European Geostationary Navigation Overlay Service ( EGNOS) is a European Differential Global Positioning System ( DGPS) as an extension system for satellite navigation. It increases regionally limited to Europe, the position accuracy of GPS 10-20 meters to 1-3 meters and is the U.S. WAAS, the Japanese MSAS and the Indian GAGAN, which also distribute their correction data via satellite (Satellite Based Augmentation System SBAS ), functional and protocol standard fully compatible. The reception of EGNOS is a clear forward view about the south.
In addition to data to improve the position accuracy EGNOS also provides information about the integrity of the GPS systems: Within 6 seconds, do the users know when positioning systems broadcast incorrect information or the reception is greatly disturbed (threshold: 20 m horizontal, 40 m vertical). This is especially important for the use of GPS in aviation.
The system is since 1 October 2009 in the official operation. In addition to the broadcast since 2006 regular EGNOS signal of one of the satellites nor the EGNOS System Test Bed ( ESTB ) is assigned.
The release for safety-of -life applications has been announced for 2010. In July 2010, the signal for the system integrity has been certified, but the live circuit failed initially ( early August ) to a software error. Since December 2010, this signal is being sent and may be used by the seller as of March 2, 2011. On 15 December 2011, the Federal Supervisory Authority for Air Navigation Services (BAF ) for Germany gave his consent.
On November 20, 2013, the European Parliament has approved the continued funding of EGNOS and the Galileo satellite navigation system in the amount of 7 billion euros for the period 2014-2020.
Background
After the artificial phase fluctuations of the civil usable C / A code of GPS ( Selective Availability ) were shut down in May 2000, term effects are the largest remaining sources of error in the ionosphere. The speed of the radio signals from the GPS satellites on passing through the ionosphere is dependent on the degree of ionization. Therefore, the running time depends not only on the distance to the satellite, but also from Ionosphärenzustand. This effect could be corrected by comparing the running times on the L1/L2-Sendefrequenzen, however, received civilian navigation devices normally only on the L1 frequency. Conventional differential GPS, based on a single reference station with known location, although allowing a highly accurate correction, but only a short distance from this station. The tomographic linking the observed of many reference stations maturities leads to an interpolated map of the electron density of the ionosphere, which allows the receivers in the entire covered by the reference station area a coarse correction.
Determination and distribution of correction data
At present, 34, later 41 reference stations ( Ranging and Integrity Monitoring Station, RIMS) in Europe, North Africa and the Middle East receive the position signals from GPS and GLONASS, and later by Galileo. Since the stations are typically much further apart than the ionosphere is high, they have to capture the ionosphere coverage, to receive the satellite just above the horizon. In order to suppress interfering multipath due to reflections on the ground, special choke ring antennas are used.
From the data of the RIMS control centers ( Master Control Center, MCC) calculate both corrections of the satellite positions and current maps of the electron density of the ionosphere for the correction of the transit times of the signals. There is not one, but four redundant MCC that can take control of EGNOS own.
Up-link stations ( Navigation Land Earth Station, NLES ) Send this correction data for nationwide distribution ( and free use ) to the geostationary communications satellites listed below. Each satellite requires a NLES. For better reliability another NLES is provided in each.
Thus a simple GPS receiver need no further reception unit, send the geostationary satellite, the data on the L1 frequency of the GPS satellites. To separate using CDMA C / A codes are used from PRN 120, regular GPS satellites use the identifier ranging from 1 to 32 following satellites are EGNOS transponders:
- Inmarsat AOR -E ( PRN 120, ID 33); Position 15.5 ° W - Atlantic
- ARTEMIS (PRN 124, ID 37); Position 21.5 ° E - Africa
- Inmarsat IOR -W ( PRN 126, ID 39; currently test system ); Position 25.0 ° E - Africa
These are to be replaced shortly by
- SES - 5, Item 5.0 ° E - Europe, Africa, started on July 9, 2012 ( PRN 136, L1 and L5 transponder)
- Astra 5B (expected second quarter 2014), position 31.5 ° E - Eastern Europe, Russia
Since the geostationary satellite in Europe but not high in the sky and are therefore to be welcomed, especially for mobile users in urban areas their signals bad, the data will also be distributed quickly over the Internet.
All outgoing records are archived and are freely available via FTP. This permits correction ( post-processing ) of GPS positions (if raw GPS data were recorded) and facilitates application development.
The freely distributed in this way correction data have only a low data rate. The much more extensive raw data of all RIMS are obtained for a fee through an access point (EGNOS Data Access Service, EDAS ). They allow a more accurate correction, especially in the environments of the RIMS, and have a guaranteed availability.
Application
Many GPS receivers support the reception of the EGNOS data. Through the EGNOS correction of position error is well below ten meters.
As a design specification is the basis that 99% of certain positions within a circle of 40 meters radius around the true position are. If this accuracy due to system anomalies can not be guaranteed, made within six seconds, a warning.
Administration
EGNOS is a joint project of ESA, the EU and the European air traffic control euro, as European Tripartite Group ( ETP ) prepared the project together. It is considered as the entry of Europeans into the satellite navigation and as a precursor to the European satellite navigation system Galileo. Responsible for design and development of the ESA. The company 's European Satellite Service Provider SAS ( ESSP ), headquartered in Toulouse ( France) operates and markets EGNOS on behalf of the EU.