When piloting deep-draught vessels in Rotterdam, whereby the pilot already comes on board about 35 miles off the coast, the Dutch Pilots' Corporation (Nederlands Loodswezen) actively makes use of a portable, autonomous navigational aid. Natural and deliberate distortions of the satellite signal (jamming and spoofing) make satellite positioning vulnerable. This vulnerability spurred Loodswezen to seek an alternative. Loodswezen and Reelektronika BV have consequently developed an alternative positioning system as a backup for satellite navigation.

By law, ships navigating the Eurogeul and Maasgeul shipping channels in the North Sea are required to carry an autonomous navigation system. Satellite positioning is the basic element for the current navigational aid. Two years of intensive development and testing off the coast of Hook of Holland have resulted in an electronic navigational aid: eDLoran (enhanced Differential Loran). The Harbour Master's Division of the Port of Rotterdam Authority contributed financially to this.

Alternative to satellite
The basis for the eDLoran system is the LOng RAnge Navigation System or LORAN. Should the satellite navigation system experience failure or disruption, then the system falls back on eDLoran. eDLoran makes use of signals transmitted by towers in England, France and Germany. Based on these signals, a location can be determined with an accuracy of less than five metres. With that, this system meets the HANAS (Port Approach Systems) specification of the government.

The port of Rotterdam is one of the busiest ports in the world, with about 32,000 ships annually visiting the port. To ensure nautical safety and a smooth traffic flow, the vast majority of those vessels must have a pilot on board when entering and leaving the port. For extra-deep draught vessels, known as geulschepen in Dutch, additional requirements apply. With the development of eDLoran, a next step has been taken towards keeping the port of Rotterdam safely and optimally accessible.