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Augmentation Systems
A Satellite Based Augmentation System (SBAS) provides system error corrections, which brings positioning accuracy to the level comparable to DGPS and also provides integrity information of the positional solution. SBAS consists of a network of ground reference stations and a set of geostationary satellites, which transmit correction data to user receivers. The correction data is modulated onto the GPS-like ranging signal in the L1 band. Three regional SBAS systems are currently available: Europe’s European Global Navigation Overlay System (EGNOS), North America’s Wide Area Augmentation System (WAAS), and Asia's Multi-functional Transport Satellite-based Augmentration System (MSAS).
Initially, SBAS was intended particularly for aviation, having in mind high integrity requirements typical for safety-of-life applications. The further development has shown that ground transportation can also significantly benefit from the high accuracy and integrity of SBAS-aided positioning. In order to increase the availability of SBAS for land navigation users, the European EGNOS system will include ground-based distribution channels of corrections/integrity information. SISNET, the first technology of this kind, is already available. The users of can receive real-time EGNOS information via the Internet. Septentrio’s PolaRx2 is the first commercially available receiver, which is able to use SISNET data. This is particularly important in urban environment, where geostationary satellites are often poorly visible due to their low elevation angles. With SISNET, SBAS-aided positioning is available everywhere 100% of the time. ESA is currently supporting a few application projects based on the use of SISNET for guaranteed high-quality ground positioning (e.g., ADvantis).
In this framework, the 'European Satellite Services Provider (ESSP)' was founded to manage EGNOS operations and provide a highly reliable source of navigation for all markets, including aviation, maritime transport, rail transport, road transport and mass-market services.
