GNSS-independent navigation – A survey

A large number of marine vessels are completely or partly dependent on the Global Navigation Satellite System (GNSS) for their navigation. In most conditions GNSS receivers provide accurate estimates of the ship's position, speed and time (PNT) but they are sensitive to intentional and unintentional jamming. Jamming and spoofing are expected to occur in the event of an armed conflict and in a grey zone scenario. The risk of jamming and spoofing is also significant in peacetime. Thus, there is a need to increase the robustness of PNT systems on a large number of ships so that they can navigate safely even in disturbed environments, in order to strengthen the civil defence. In this report alternative techniques for GNSS-independent navigation are summarized. In addition to that a state-of-the-art analysis of bathymetry-aided navigation (terrain navigation based on depth data) as a complement to GNSS, is provided.