R-Mode - The Potential to Support Resilient PNT Through the re-use of Existing Maritime Infrastructure

Abstract

The IMO e-Navigation concept supports the developed of resilient positioning, navigation and timing (PNT) information. The need for resilient PNT well documented and it is recognised that the use of a number of technically dissimilar systems are required to ensure resilient PNT is achieved. Global Navigation Satellite Systems (GNSS) are expected to remain the primary means of navigation at sea; however additional supporting and complementary systems are required to give resilient PNT. One candidate system which could provide alternative positioning and timing information is called R-mode, or ranging mode. This is the name given to the provision of a new ranging signal to marine radio beacon 300 kHz transmissions and AIS base stations transmissions, from which the mariner could then potentially calculate their position, independently to GNSS. The concept of such a system was developed under the ACCSEAS project, which considered a number of potential e-Navigation solutions, resilient PNT being one. The ACCSEAS project has been introduced and discussed at ION conferences; however, this paper will focus on R-mode. This paper will report on the aims and objectives of R-Mode, the results of the feasibility study that was produced by the ACCSEAS project, review the development of the concept to date and report on the development and test of a prototype marine beacon broadcast and receiver. It will review the performance of the prototype system and then consider the proposed way forward, both from a local perspective, but also from the wider international perspective for the use of such a system world-wide. The latter will consider the development path, international standardisation activities and the questions which need to be addressed. The paper will describe the current developments for R-mode in both the marine beacon and AIS variants, raising awareness and seeking support for further investigation and development of this potentially important approach to support resilient PNT across the maritime sector.