This report reviews the broad range of options for R&I (Resilience and Integrity) PNT that have been identified in previous studies, analysing the potential contribution of each option. Candidates include wide-area systems such as eLoran and the Satelles System Timing and Location (STL), regional area systems such as MF R-Mode and VDES R-Mode and local-area systems with local infrastructure such as LOCATA at ports. The study includes the use of ships’ radars with coastal Enhanced Radar Beacons (‘eRacons’) with positioning through a process referred to as “radar absolute positioning”. In addition, the work includes a description of ship-based systems such as dead reckoning systems based on speed log and gyro compass and electronic visual aids such as the ePelorus.