There are marine radiobeacon DGPS services in over 30 countries throughout the world including the majority of North West European States. With advances in technology, the signals from radionavigation systems have progressively transcended national boundaries to provide long-range transmissions from a network of satellite and terrestrial stations. This has significant benefits for the safety of navigation since it enables a consistent means of navigation throughout all phases of the voyage, during the day or night and in conditions of reduced visibility. Such systems will also help with improved voyage planning to reduce ship operators' costs. A high level of availability of the right mix of aids to navigation systems also plays some role in determining which ships will visit our ports and in demonstrating that effective measures have been taken to minimise the risk of pollution from ships.