Software Receiver Implementation of SBAS Guidelines for Maritime Including RAIM

Global Navigation Satellite System (GNSS) and SBAS, in particular, are widely used in many applications due to its enhanced accuracy and integrity provision. Its compliance with the performance requirements in Maritime specified in IMO Res.A.1046 is under continuous monitoring and assessment and new tools are being developed for this purpose. This work presents a contribution to an existing tool (i.e. software receiver and monitoring tool) where the last version of the SBAS Guidelines for shipborne manufactures has been implemented. This implementation includes the processing of recommended SBAS messages together with a classic RAIM Algorithm. The main objective of this publication is to present this software and the kind of assessments which allows to perform so that it can be used by any maritime authority and any chipset/receiver manufacturer interested. The software receiver will be available for free and will help to support the standardisation process of SBAS in IEC. The software tool used is gLAB developed by Universitat Politecnica de Catalunya. It is an educational tool promoted by the European Union, part of the EDUNAV program and designed to help future European generations to easily learn the fundamentals of GNSS. The identified gLAB version as a starting point in this case is the 5.4.4, which has been modified in order to include this specific implementation of SBAS and RAIM according to the IALA guidelines. In order to validate this new tool a performance analysis was made considering an initially set of 84 stations, although some of them are discarded in order to perform the analysis under fault-free receiver conditions. Thereby, a clear view about the performance in coastal and also inland waters can be presented. Part of the data used is provided by the IGS14 European network through public NASA-CDDIS1 , whereas the other source of information is the EDAS RIMS2 . This assessment covers 24 months, from the 1st of October 2018 to the 30th September 2020. It should be noted that previous studies have already assessed the coverage, availability and continuity of SBAS in the European territory. However, those previous analysis only use the SBAS messages and the navigation files as inputs for the calculation, but they do not consider the observation data, unlike this present study. Therefore, changes are expected in the results, since the observation files introduce a receiver processing dependence.