R-Mode - An alternative maritime navigation system to GNSS

Abstract

Global Navigation Satellite System (GNSS) is a system that makes it possible to perform positioning and timing almost everywhere with an accuracy of several meters. You only need a GNSS receiver and an antenna. Over the years, the size of both has been significantly reduced. Furthermore, each GNSS offers an open service. As a consequence, we find GNSS receivers as the primary source of position and timing information in different economic sectors, especially in the various modes of transport and in the area of logistics. In addition, we use this practical tool in research and in private. Unfortunately, our position and time sensors rely on signals that are very weak when they arrive at the Earth's surface. Interference is likely and is brought about deliberately. Furthermore, system failures occurred in the past and the ionosphere causes a variable delay in the signals. To circumvent that we rely on a system, which might not work with the expected performance, we need one or several alternative navigation systems and sensors. They are important for identifying times when GNSS is not usable and taking over the provision of position and time information. The maritime sector benefits a lot from GNSS. GNSS receivers are directly or indirectly integrated into a lot of bridge systems to show their own position, heading, speed and time. Furthermore, it is used to present the traffic situation based on one’s own position and the position of surrounding vessels which usually provide position, navigation and static information using the Automatic Identification System (AIS). Reliable PNT information is key to avoiding groundings and collisions of vessels. Ranging Mode (R-Mode) is an approach to use existing maritime communication infrastructure to provide synchronized ranging signals that can be used as a maritime terrestrial navigation service as backup for GNSS. At the moment especially maritime radiobeacons and the AIS base stations with its successor VDES are used as source for R-Mode signals. A first large-scale R-Mode test bed was established in the southern Baltic Sea (Figure 1). The talk will give you an overview about the current status of R-Mode research and development. Based on the stated need for an alternative technology for positioning and timing in the maritime domain, the fundamental concept and theoretical performance of R-Mode will be explained and the results of trials will be presented. They show that R-Mode is a candidate for a cost-efficient terrestrial navigation system which meets the requirements for the coastal navigation.