Document Type

Conference Proceeding

Date of Original Version



Position, Navigation, and Timing (PNT) is part of the critical infrastructure necessary for the safety and efficient of vessel movements, especially in congested areas such as the North Sea. GNSS (primarily GPS and GLONASS) has become the primary PNT source for maritime operations. The GNSS position is used both for vessel navigation and as the position source for AIS.

Unfortunately, GNSS is vulnerable to jamming and interference – not intentional and unintentional. This can lead to the loss of positioning information or even worse, to incorrect positioning information. The user requirement is for dependable PNT information at all times, even under GNSS jamming conditions. One potential source of resilient PNT services is Ranging Mode (R-Mode) using signals independent of GNSS.

The German Federal Waterways and Shipping Administration has contracted for a feasibility study of R-mode using MF-DGNSS and VHF AIS signals as well as those signals in combination and in combination with eLoran. The first part of the study focused on the feasibility of using MF-DGNSS signals for ranging and timing. It examined the state of the art, identified potential solution methods, and, after examining Pros and Cons of the various options, selected a few options for further study. Part 2 examined the proposed solutions in depth and identified the modifications required for both the reference stations (transmitters) and user equipment (beacon receivers). Part 3 and 4 of the study repeated Parts 1 and 2, but using AIS signals rather than MF. Part 4 of the study examined the possibility of combining MF and AIS R-mode or combining MF R-Mode and eLoran.

This paper presents the results of this study including recommended R-Mode implementations and bounds on the positioning performance using the various R-Mode methods. Included are predictions of DGNSS and AIS R-Mode coverage and the resulting HDOP using existing and preposed DGNSS and AUS sites with specific detail in the area of the planned test bed in the North Sea.