Eurofix

Eurofix. It is an integrated navigation and data link system that combines the capabilities of the Global Positioning System with the signal structure of the LORAN-C radio navigation network. Developed primarily to enhance the integrity and accuracy of GPS for safety-critical applications, it transmits Differential GPS corrections and other data via existing LORAN-C transmitters. This hybrid approach provides a robust, terrestrial backup to satellite navigation, particularly valuable for maritime navigation and aviation in regions like the North Sea.

Overview

Eurofix represents a significant innovation in radio navigation, designed to address vulnerabilities in sole-means GPS by utilizing the established, high-power ground wave propagation of the LORAN-C system. The system was conceived by researchers at Delft University of Technology in the Netherlands and further developed in collaboration with organizations like the United States Coast Guard. Its core function is to broadcast DGPS correction messages, integrity data, and other information by modulating the Group Repetition Interval pulses of LORAN-C signals. This creates a wide-area, reliable data channel without requiring new transmitter infrastructure, serving as a complementary Position, navigation, and timing source for users in Europe and beyond.

Technical principles

The technical operation of Eurofix is based on a method known as Time Division Multiplexing applied to the LORAN-C signal. Data is encoded using a technique called Pulse Position Modulation, which slightly shifts the timing of individual LORAN-C pulses within a chain's transmission sequence. This modulation is subtle enough not to interfere with the primary radionavigation function of LORAN-C for users without Eurofix receivers. Specialized receivers, such as those developed by Fugro or TNO Defence, Security and Safety, decode these timing shifts to extract the DGPS correction stream. The corrections are then applied to GPS signals, significantly improving positional accuracy and providing crucial integrity monitoring alerts if the GPS signal becomes unreliable.

Development and implementation

The development of Eurofix began in the late 1980s at the Delft University of Technology, led by scientists like B. D. O. Anderson. Key trials and demonstrations were conducted throughout the 1990s, including successful tests in the North Sea coordinated with the Dutch Ministry of Transport, Public Works and Water Management. A major implementation milestone was the upgrade of the LORAN-C transmitter at Sylt, Germany, to broadcast Eurofix signals. The system's operational management and service provision were later taken over by the multinational company Fugro, which integrated it into its commercial Starfix and other DGPS service networks. This implementation proved the viability of using LORAN-C as a robust data link for safety-of-life applications.

Applications and users

The primary application of Eurofix is in enhancing safety for maritime navigation, particularly for harbor approach and waterway management in congested areas like the Port of Rotterdam and the English Channel. It is used by vessel traffic service centers, offshore survey vessels, and dredging companies requiring high-precision positioning. In aviation, it has been evaluated for non-precision approach and airport surface movement guidance. Key institutional users have included the Royal Netherlands Navy, the German Federal Waterways and Shipping Administration, and various hydrographic offices. The system also served as a technical precursor and influence for modern enhanced LORAN concepts and other terrestrial backup systems for GNSS.

Relationship to other systems

Eurofix exists in a symbiotic and complementary relationship with several other radionavigation systems. It is fundamentally dependent on both the American GPS and the international LORAN-C chains, such as those operated by the United States Coast Guard and European nations. It directly complements other wide-area DGPS services like the United States Coast Guard's National Differential GPS and the International Association of Marine Aids to Navigation and Lighthouse Authorities networks. Technologically, it shares principles with the Japanese Loran-C data channel system. As a concept, it informed later developments in GNSS augmentation, including discussions on the role of eLORAN as a resilient Position, navigation, and timing backup within national infrastructure plans in the United Kingdom and the United States.

Category:Radio navigation Category:Global Positioning System Category:Aviation safety systems