DGPS can provide accuracies of 5 metres (95%) in moving applications and even better in stationary applications, by cancelling out most of the natural and man-made errors arising from normal GPS measurements. DGPS works by having a fixed receiver at a known ground-based reference station (e.g. GLAs marine radiobeacon stations) which continuously monitors the GPS errors and transmits corrections to the measurements taken by mobile receivers operated by users of the system.

The GLAs' DGPS service is intended to offer accuracies for general navigation of < 10 metres for vessel position-fixing in areas where the freedom to manoeuvre is restricted. The intended coverage area of the GLAs' DGPS Service is 50 nautical miles around the coasts of the United Kingdom and the Republic of Ireland.