SBAS Service Based in IMO Res. A.1046 (27): EGNOS Maritime Performance

Pedro Pintor, Carlos de la Casa, Manuel Lopez-Martinez, Roberto Roldan

Abstract:	The European Geostationary Navigation Overlay Service (EGNOS) augments the open public service offered by the GPS. EGNOS makes GPS suitable for safety critical applications. EGNOS is conceived as an integral part of a multi–modal inter–regional Satellite-Based Augmentation System (SBAS) service that integrates systems designed according to the same standard (RTCA MOPS 229) such as US WAAS, Japanese MSAS, GAGAN in India and SDCM in Russia. EGNOS provide over Europe both corrections and integrity information about the GPS system, delivering opportunities for accurate positioning improving existing applications or developing a wide range of new ones. 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. A new EGNOS safety-of -life service for maritime is currently under development. EGNOS can complement DGNSS in poorly covered environments or where there is no infrastructure for the provision of enhanced accuracy and integrity information. EGNOS functionality is supported by most of the maritime GNSS receivers used in both merchant and leisure market segments and a Guidelines to use the integrity information is under development within RTCM. IMO Res. A.1046 (27) sets a serie of performance requirements for systems to be recognized as components of the worldwide radionavigation systems (WWRNS) by IMO in terms of Ocean Waters and Harbour entrances, Harbour approaches and Coastal waters operations that are met by EGNOS. For the maritime community, an EGNOS maritime service based on IMO Res. A.1046 (27) is definitely of interest. Since 2014 the European GNSS Agency (GSA) and the EGNOS service provider (ESSP SAS) are working together on a wide range of actions to foster the use of EGNOS among merchant vessels towards a potential EGNOS safety-of-life service based on IMO Res. A.1046 (27). The various technical tasks are: 1) The first task, which is presented in detail in this paper, is the identification and definition of a set of service performance parameters required for a complete characterization of EGNOS safety-of-life maritime service. The list of service performance parameters is derived from the list in IMO Res. A.1046 (27) and includes Signal Availability, Horizontal Accuracy 95%, Position update rate, Service Coverage for Ocean Waters and two additional parameters such as Service Continuity and Time To Alarm for Harbour entrances, Harbour approaches and Coastal waters. Additionally to IMO’s, a new parameter is needed to characterize EGNOS maritime service because the particularities of this radionavigation aid. This parameter is called Service Availability and indicates the percentage of time a position solution is available in a specific location calculated using EGNOS. The rationale behind the need of this parameter is explained in this paper following the recommendations in IALA Guidelines 1112 on performance and monitoring of DGNSS services. 2) The second task is a preliminary performance assessment of the EGNOS SoL service based on IMO Res. A.1046 (27) for a 15 months period during 2016 and 2017. The performance parameters listed and detailed in the first task are calculated using real data to know what level of performance was attained by EGNOS .. The assessment was done using both EGNOS RIMS and fault-free receivers fed with actual data. The performance is shown for each performance parameter in the list and for Ocean Waters and Harbour entrances, Harbour approaches and Coastal waters operations. A similar six-month analysis reveals that performance results are positive for Ocean Waters and promising for Harbour approaches. The paper also includes Service Coverage maps understood as a preliminary service commitment area representing where EGNOS maritime service based on IMO Res. A.1046 (27) is adequate. 3) The third task deals with the use of EGNOS information to provide integrity according to the requirements defined in IMO Res. A.1046 (27). IMO integrity concept addresses GPS system failures and does not consider local sources such as multipath, shadowing effects or local interferences. This is also the approach in DGNSS. The EGNOS integrity information is provided at system level, ensuring that the satellite orbit and clock and ionospheric correction errors are bounded for each GPS satellite line of sight. 4) The extensive work to develop SBAS receiver Guidelines according to IMO Res. A.1046 (27) is the fourth task. Among others, its purpose is to identify, the minimum set of SBAS messages to be processed by a receiver, the way messages should be processed as well as the system alerts applicable to comply with the requirements or the tests to be performed by the manufacturers. Guidelines are also intended to support the process of integrating SBAS to multi-system shipborne radionavigation receivers. This work is being done within RTCM SC 104. For the first time, this paper presents two of the four the technical activities being executed by GSA and ESSP to pave the way for the EGNOS maritime service based on IMO Res. A.1046 (27) such as the list of performance parameters to completely characterize the SBAS maritime performance and the level of EGNOS performance attained for maritime and introduces the SBAS integrity concept for maritime and the SBAS maritime receiver Guidelines.
Published in:	Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017) September 25 - 29, 2017 Oregon Convention Center Portland, Oregon
Pages:	1354 - 1372
Cite this article:	Pintor, Pedro, la Casa, Carlos de, Lopez-Martinez, Manuel, Roldan, Roberto, "SBAS Service Based in IMO Res. A.1046 (27): EGNOS Maritime Performance," Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017), Portland, Oregon, September 2017, pp. 1354-1372. https://doi.org/10.33012/2017.15111
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