GPS (Global Positioning System) is the principal Global Navigation Satellite System (GNSS) used for radionavigation position fixing by mariners and underpinning navigation, situational awareness and communications.
IALA radiobeacon DGNSS remains the internationally accepted means of providing differential GNSS (DGPS at present) corrections and integrity information to maritime users. It is defined internationally and is the worldwide standard. Regional harmonisation of frequencies and station identification numbers are carried out under ITU agreements, coordinated by IALA.
GLA DGNSS
The GLAs operate 14 Differential Global Positioning System (DGPS) reference stations (figure below also shows the far field monitoring sites and the monitoring and control stations) which provide corrections to mariners in the vicinity, enabling them to improve their positional accuracy and to monitor integrity.
The GLA DGPS Network, showing the location of the DGPS stations, monitor and control stations and far field monitor sites.
The GLAs operate this service as a joint venture, although each authority is responsible for the maintenance and monitoring of those reference stations within their areas of responsibility. As an Aid-to-Navigation (AtoN), the GLAs have to ensure that this service meets the international operational requirements as set by the International Maritime Organization (IMO).
Performance of a radionavigation broadcast service is defined by five basic components: accuracy, integrity, availability, coverage and continuity (IALA-R121, IMO Resolutions A.953(23) and A.915(22)).
Several other regional augmentation systems exist. Completed systems include (but are not limited to) the European Geostationary Navigation Overlay Service (EGNOS) and the US WAAS, as well as the Japanese MSAS. India's GAGAN is currently under construction.
