SBAS Guidelines for Shipborne Receiver: EGNOS Performance Based on IMO Res. A.1046 (27)
Authors: Magdaleno Sergio , Lacarra Elisabet , de la Casa Carlos , López Manuel , Roldán Roberto , Blanco Nuria 
Published: July 2019

The European Geostationary Navigation Overlay Service (EGNOS) augments the open public service offered by the GPS in Europe making suitable the use of GPS for safety critical applications. EGNOS is designed according to the same standard [ICAO SARPs, 2018] such as US WAAS, Japanese MSAS, GAGAN in India, SDCM in Russia and KAAS in South Korea and provides over Europe both corrections and integrity information about the GPS system. As the European SBAS, EGNOS offers three services: Open Service, Safety-of-life Service and EDAS. In general, the EGNOS Safety-of-life (SoL) Service is intended for transport applications in different domains (and currently in use by Aviation) where lives could be endangered if the performance of the navigation system is degraded below specific accuracy limits without giving notice in the specified time to alert. This requires that the relevant authority of the particular transport domain determines specific requirements for the navigation service based on the needs of that domain.

Even if the main objective of the SBAS systems is the civil aviation community, the advantages provided by this technology are very useful to users from other domains. In this sense, a new EGNOS service for maritime is currently under development with the objective to complement the existing maritime radionavigation systems (e.g. DGNSS) in the European region for enhanced accuracy and integrity information where there is no backup infrastructure or in poorly covered environments.

One of the steps needed for the development of this new EGNOS maritime service is the definition of a minimum set of recommendations for receiver manufacturers to provide them with a clear view on how to design their SBAS receivers to be compliant with the requirements defined for such a service. For that, EC, GSA, ESA and ESSP SAS have been working together since 2016 to develop guidelines for manufacturers for the implementation of SBAS in shipborne receiver. These guidelines, developed in the frame of the SBAS Working Group created in the Special Committee (SC) 104 on Differential Global Navigation Satellite Systems (DGNSS) of Radio Technical Commission for Maritime Services (RTCM), define a minimum set SBAS messages to be compliant with the International Maritime Organization (IMO) Resolution A.1046 and additionally provide a test specifications.

This paper presents a summary of these SBAS guidelines as well as the preliminary list of tests that must be fulfilled to be compliant. Additionally, a preliminary performance assessment of the EGNOS maritime service based on IMO Res. A.1046 (27) for a 24-months period during 2016, 2017 and 2018 is presented. The performance parameters are calculated using real data to show what level of performance was attained by EGNOS. The assessment was done using both EGNOS ground monitoring stations (RIMS) and fault-free receivers, based on these guidelines, fed with actual data. The performance is shown for each performance parameter defined in the IMO Res. A.1046 (27) and for navigation in Ocean Waters and coastal waters, harbour entrances and harbour approaches. The paper also includes Service Coverage maps representing where EGNOS maritime service based on IMO Res. A.1046 (27) is fulfilling the requirements.

Furthermore, GSA and ESSP, with the collaboration of The Norwegian Coastal Administration and Hurtigruten Cruises, carried out a GNSS data collection campaign of 10 days along the Norwegian coast with a trajectory through Trondheim to Kirkenes and Kirkenes to Bergen in February 2018. The aim of this data campaign was to assess EGNOS performance at user level in the maritime domain at high latitudes in Europe. The data campaign includes the navigation outside the MT27 region defined in EGNOS at that moment (70ºN). A performance assessment of EGNOS using some commercial receivers and a software receiver in line with the SBAS guidelines will be presented, showing the observed accuracy and availably results of the EGNOS solution.