GNSS Augmentation Systems in the Maritime Sector

The provision of differential global positioning system (DGPS) corrections, together with integrity information, using non-directional medium frequency (MF) marine radiobeacons is well established and has proved successful. However, the new signals to be available from GPS (L2C and L5) together with those transmitted from Galileo (E5a and E5b) will undoubtedly impact on the DGPS service, necessitating modification to enable augmentations to be provided for the new frequencies, as well as that provided for the L1 signal. In addition, there are a number of emerging systems, such as space-based augmentation systems (SBAS), terrestrial regional augmentation systems (RAS), on-board systems and proposed Galileo services that will be available in the near future. These new systems could either complement or compete with the maritime DGPS service and may well provide additional capability to enable new applications. Furthermore, maritime requirements have evolved considerably since the design of the DGPS service. These requirements not only cover general navigation by conventional craft but now also include high speed craft (HSC), fast manoeuvrable craft (FMC) and the plethora of other applications that need position, velocity and time inputs. The current snapshot of these requirements has been promulgated by the International Maritime Organization in Resolution A.915(22). However, these requirements will evolve as new applications develop and system capabilities are enhanced. In response to these changes, the General Lighthouse Authorities (GLAs) of the UK and Ireland have launched a major study to support the development of future radionavigation systems policy. The study has assessed future performance of the global components of GNSS (GPS, and Galileo) in the maritime context. The study is also assessing the contribution that can be made by the various augmentation systems (regional, local and autonomous) to meet unfulfilled requirements and, therefore, enable additional applications. The results generated to date suggest that, in order for the basic global requirement for general ocean, coastal and port approach navigation to be met, a combined GPSGalileo system will be required, operating on multiple frequencies. Current augmentations, notably the IALA DGPS system and the EGNOS service, will meet this requirement but do not give the global coverage that is needed. The more stringent requirements of port navigation and other operations, needing regional and local coverage, can only be met through local augmentation systems and may require the current IALA DGPS system to be upgraded to operate on multiple frequencies. The most stringent requirements for special operations would then require implementation of carrier phase systems which would have to be designed and located to support specific applications. The utility of integrated inertial sensors will be investigated as well as the capabilities of additional augmentation systems, such as Eurofix and the potential for using ranging signals from marine radiobeacons as well as LORAN-C stations. Future phases of the study will then assess the opportunity to integrate maritime and non-maritime systems to enable mutual benefits, as well as determining the value, pros and cons of potential future system mixes using cost-benefit and risk analysis in a scenario driven methodology.