EGNOS open service guidelines for receiver manufacturers

Satellite Based Augmentation Systems (SBAS) consist of a network of reference stations distributed over a wide area that monitor the status of Global Navigation Satellite Systems (GNSS) such as GPS or GLONASS. These reference stations send the data collected on the status of GPS to a master station where differential corrections and integrity information are computed for every monitored satellite. Once these are calculated, a ground Earth station uplinks them to Geostationary satellites (GEO) which broadcast this information to the end user. Examples of SBAS systems are the European Geostationary Navigation Overlay Service (EGNOS), the U.S. Wide Area Augmentation System (WAAS), the Japanese Multifunctional Transport Satellite Augmentation System (MSAS), and the Indian GPS and GEO Augmented Navigation (GAGAN). In the recent years SBAS systems have been topic of much study for Safety of Life (SoL) applications. User communities such as civil aviation have done extensive use of this kind of systems relying on the accuracy benefits they provide but above all on the use of integrity information. SBAS enabled GNSS receivers for these applications have been designed and manufactured according to recognized standards [1]. These standards have been created and are targeted solely to SoL applications. As a result, receiver manufacturers have a clear view on how to design their products for SBAS SoL service. However, this is not the case for the design of SBAS receivers to be used for services other than SoL applications. Focusing on the particular case of EGNOS, besides the SoL service (declared operational on March 2011), the Open Service (OS) has been readily available and free to the public since October 2009. Since then most manufacturers have designed EGNOS OS receivers by only partially following SoL recommendations [1]. This has led to a number of different implementations that in some cases may not be optimal. The objective of this paper is to present a set of guidelines for GNSS receiver manufacturers on how to make use of the EGNOS broadcast messages to improve their positioning accuracy and availability for OS and Non-SoL services.