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Radionavigation - GNSS/DGNSS

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.


The GLAs operate 14 Differential Global Positioning System (DGPS) reference stations (the 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.

Image: GLA DGPS network

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).

The coverage area of a radionavigation broadcast service is defined by the four basic Required Navigation Performance (RNP) parameters: accuracy, integrity, availability, and continuity (IALA-R121, IMO Resolutions A.1046(27) ).