Radar Aids to Navigation in the age of GNSS

摘要

Global Navigation Satellite Systems (GNSS - in particular GPS) have become the primary means of navigation in many maritime applications. However, the vulnerability of GNSS to accidental or deliberate interference is well known and the need for more than one position input to e-Navigation is recognised. Radar aids to navigation, in particular radar beacons (racons), provide an independent means of positioning fixing, situational awareness and collision avoidance. They are highly valued by mariners, but changes in radar technology may limit their effectiveness in the future. IMO MSC79 resolution 192(79) removed the requirement, from 1 July 2008, for S-band radar to trigger Radar Beacons. This was intended to encourage manufacturers to develop new types of radar; known as New Technology (NT) radar. The GLAs have conducted racon trials with an NT Radar fitted to Commissioners of Irish Lights (CIL) Vessel Granuaile. The trials were conducted in the Dublin Bay, Codling and Arklow areas of the Irish Sea, where there are a number of fixed and floating CIL AtoNs fitted with different types of racon. Trial results showed that the NT radar tested did trigger racons, but at a significantly reduced range. However, increasing racon receiver sensitivity appears to restore much of the lost range with the NT radar. Given the increased reliance on GNSS and the need for integration of systems with the introduction of e-Navigation, it is argued that the service provided by racons will become more important in the future, particularly as they provide information independent of GNSS via a separate receiver (radar). This paper considers various ways of enhancing the service provided by racons, such as providing a position and name of station encoded in the response. This paper concludes that consideration should be given to modifying existing racons to improve their response to NT radars. This would need to be done in consultation with racon and radar manufacturers. Further trials should also be carried out to confirm that the results obtained apply to other types of NT radar. The results have been made available to the International Marine Aids to Navigation and Lighthouse Authorities (IALA), to provide a general awareness of the potential effect of NT radars on racon performance and so that the standards for radar aids to navigation can be reviewed and strategic options can be discussed, in the light of increased dependence on GNSS.