EGNOS Performance Along the Baltic Sea with a Maritime Receiver During 3 Months

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This article analyses EGNOS (European Geostationary Navigation Overlay Service / SBAS in Europe) performance in high latitudes during a long period of time (three months) in a real maritime environment with a maritime GNSS receiver. The purpose is to demonstrate the benefits of EGNOS for maritime navigation, showing that EGNOS L1 service is compliant with the operational requirements defined in the IMO Res. A.1046 (27) for ocean waters, coastal waters and harbour entrances/approaches. The EC (European Commission) and EUSPA (European Union Agency for the Space Programme) are assessing an EGNOS L1 Maritime Service with the objective to complement the existing maritime radio-navigation systems (e.g. IALA DGNSS). Maritime community is interested in using SBAS for ocean waters, coastal waters and harbour entrances/approaches considering operational needs (IMO Res. 1046 (27)), especially where there is no back-up infrastructure or in poorly covered environments. The EGNOS L1 Maritime Service aims at providing pseudo-range corrections and alert information to the GPS L1 signals for maritime navigation, obtaining enhanced accuracy and integrity information over Europe. A GNSS maritime campaign has been performed in the Baltic Sea between September 1 st to December 1 st 2021 in order to analyse the EGNOS performance in the North of EGNOS service area. The vessel sailed for 3 months over the coastal waters of eastern Denmark, southern and eastern of Sweden, western and southern of Finland, Latvia, Lithuania, docking in ports such as Munkebo (Denmark) to Porvoo (Finland), going through Melnrage (Lithuania), Riga (Latvia), Nynäshamn (Sweden), Stockholm (Sweden), Gävle (Sweden), Uddebo (Sweden), Kokkola (Finland) and Hamina (Finland). One maritime receiver and two high-end receivers were installed on board the vessel, an oil tanker. The maritime receiver was configured to use SBAS in order to analyse its navigation performance in postprocessing. Whereas one high-end receiver was operating in multi-frequency multi-constellation mode in order to compute the “real” trajectory in post-processing using Precise Point Positioning (PPP) techniques, the second one has been used to obtain both EGNOS and GPS standalone performance with a specific software. For the assessment, the EGNOS navigation errors will be obtained with respect to the “real” PPP post-processed trajectory. Apart from accuracy, availability of the SBAS position solution will be computed through the complete route. Then, the performance obtained with the maritime receiver will be compared with respect to the operational requirements defined in the IMO Resolution A.1046 (27) for ocean waters, coastal waters and harbour entrances/approaches to demonstrate the feasibility of EGNOS for those maritime applications. Additionally, EGNOS accuracy will be compared with respect to GPS standalone ones in order to show EGNOS added value in terms of position errors, thus providing a more efficient navigation. In addition, alarms triggered by the maritime on board receiver will be also assessed. Shipborne receivers display alarms and alerts during the operation, which include RAIM status, HDOP checks and signal status. Therefore, those alarms will be identified throughout the voyage to further analyse the performance during those periods, assessing the position errors and the causes behind those alerts. Preliminary results showed EGNOS accuracy below 1 meter (95%-percentile) and EGNOS positioning availability over 99% in the EGNOS maritime receiver during the three-month dynamic data campaign. Additionally, EGNOS horizontal position errors were lower than 1.2 metres during the complete route, which met with the wide margin of 10-metre IMO requirement for coastal waters and harbour entrances/approaches and the 100-metre IMO requirement for ocean waters. As a preliminary conclusion, the 3-month GNSS maritime campaign over the Baltic Sea confirms that EGNOS positioning is compliant with the operational requirements defined in the IMO Res. A.1046 (27) for ocean waters, coastal waters and harbour entrances/approaches, confirming the expected benefits from the future EGNOS Maritime Service.