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GPS Jamming and the Impact on Maritime Navigation

  • Alan Grant (a1), Paul Williams (a1), Nick Ward (a1) and Sally Basker (a1)

Versions of this paper were first presented at the Royal Institute of Navigation GNSS Vulnerabilities and Solutions Conference held at Baska, Croatia in September 2008 and the Royal Institute of Navigation NAV 08 Conference held at Church House, Westminster, London in October 2008.

The US Global Positioning System (GPS) is currently the primary source of Position, Navigation and Timing (PNT) information in maritime applications, whether stand-alone or augmented with additional systems. This situation will continue in the future with GPS, possibly together with other Global Navigation Satellite Systems (GNSS) e.g. Galileo, being the core PNT technology for e-Navigation – the future digital maritime architecture. GPS signals, measured at the surface on the Earth, are very weak. As such, the system is vulnerable to unintentional interference and jamming, resulting in possible denial of service over large geographical areas. The result of such interference could be the complete failure of the mariner's GPS receiver or, possibly worse, the presentation to the mariner of hazardously misleading information (HMI) for navigation and situational awareness, depending on how the GPS receiver reacts to the jamming incident. Recognising this, the General Lighthouse Authorities of the United Kingdom and Ireland (GLA), in collaboration with the UK Ministry of Defence (MOD) Defence Science and Technology Laboratory (DSTL), have conducted a series of sea-trials with the aim of identifying the full effects of GPS jamming on safe navigation at sea.

This paper presents the key findings of these trials and provides important information on the effect of GPS denial. The GLA are playing a pivotal role in the establishment of eLoran as an independent source of PNT, taking advantage of eLoran's complementary nature, having dissimilar failure modes to GPS and the future GNSS. This paper provides information on the performance of an eLoran receiver in an area of GPS service denial. The paper presents the rationale for the work, details the system architecture employed, the data gathering efforts and finally the data analysis procedures, results and conclusions.

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[1]Vulnerability Assessment of the Transportation Infrastructure relying on the Global Positioning System’, Final Report, prepared by John A Volpe National Transportation Systems Center for Office of the Assistant Secretary for Transportation Policy, US Department of Transportation, August 29 2001,·6.pdf
[2]2020 The Vision: Marine Aids to Navigation Strategy’, General Lighthouse Authorities of the United Kingdom and Ireland, October 2004.
[3]‘The General Lighthouse Authorities’ Radio-Navigation Plan', The General Lighthouse Authorities of the United Kingdom and Ireland, May 2007.
[4]‘The Case for eLoran’, The General Lighthouse Authorities' Research and Radionavigation Directorate, 8 May 2006.
[5]Adoption of a National Backup Service to GPS’, United States Department of Homeland Security Press Release, February 2008.
[6]Loran's Capability to Mitigate the Impact of a GPS Outage on GPS Position, Navigation, and Time Applications’, Narins, M. (Programme Manager), Prepared for the Federal Aviation Administration Vice President for Technical Operations Navigation Services Directorate, FAA, March 2004.
[8]“The hunt for RFI – Unjamming a Coast Harbor”, Clynch. J, et al, GPS World, January 2003. (
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The Journal of Navigation
  • ISSN: 0373-4633
  • EISSN: 1469-7785
  • URL: /core/journals/journal-of-navigation
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