GPS Jamming - is it just a lot of noise?


Global Navigation Satellite Systems (GNSS) threats and vulnerabilities have received considerable exposure in open publications and in the press in recent years. Although a number of studies have been undertaken, substantial gaps remained in our understanding of the impact that illegal jammers and other disturbances cause to PNT users in operational situations. Spoofing is now also emerging as a credible threat to PNT Devices, with GPS threats built from SDRs. The much-trumpeted eLoran, portrayed by some as a panacea, offers no protection at all against spoofing.

In simple terms, Jammers swamp the reception of radio signals, causing "an outage" at a receiving device. Spoofers cause a Device to output wrong information, that nevertheless appears to be correct, thereby deceiving the user or application. Techniques exist to counter both types of threats, but these are not widely implemented outside the military.

I ran project STAVOG on GNSS threat quantification and testing 6 years ago and showed the limitations of operational equipment that, despite meeting all certification needed for safe operation in maritime environments, was unable to cope with interference. More recently, we realised that a major technical gap had been left by Government all other researchers (except our friends at Nottingham Scientific, NSL), namely an understanding of what interference and jamming threats actually existed "in the wild". My team ran project GEMNET as a collaborative activity with Ordnance Survey to further the state of knowledge and start to address these gaps. Our work assessed the state of knowledge in this field and conducted field measurements and Lab work.

  1. Hundreds of jammers were observed over 100 observation days;
  2. These threats were much weaker than the "hyped" stories claim, generally causing no impact on operational GNSS equipment.

We do not believe that any jammers were specifically targeted at GEMNET monitor sites, and our focused Lab work showed that such an attack would probably cause problems. Governmental, CNI, and others for whom GNSS dependence may be safety critical or mission critical need to address PNT robustness. They need to appropriately assess their risks, and take informed decisions about robustness of services that depend on positioning and/or timing. They should consider both neighborhood threats and threats specifically targeted at them.

I  provide technical advise to clients, and run tutorials for industry and post grad students on GNSS Threats & Vulnerabilities and on Robustness of Position, Navigation & Timing. Please contact me for more information. Those interested may also wish to read the following publications:

  1. Dixon, C.S., S. Hill, A. Ucar, G. Ameer, M. Greaves, P. Cruddace; GNSS Threat Quantification in the United Kingdom in 2015. Coordinates Magazine, January 2016
  2. Dixon, C.S; Concerns on the Evidential Quality of Automatic Identification System (AIS) Records. C-SIGMA VI, London, 7-8 November 2015
  3. Dumville, M., W. Roberts, J. Hammond, M. Trosh, C. Dixon, S. Hill, P. Lindsay; Quantitative Assessment of the Impact of GNSS Threats on Governmental Applications and Receivers (QUASAR). ION GNSS+ 2015. September 2015, Portland OR
  4. Hill, S., C.S. Dixon, A. Ucar; In-Field Demonstration of GNSS Systems Resilience to Interference. RIN International Navigation Conference (INC 2015), Manchester, 24-26 February 2015
  5. Dixon, C.S, S. Hill, G. Buesnel, A. Ucar, P. Alfaro, and J. Beasley ; UK GNSS Performance Quantification Network. ION GNSS 2014, September 8-12, 2014. Tampa, Florida
  6. Dixon, C.S., S Smith, A Hart, R. Keast, S Lithgow, A Grant, J Šafář, G Shaw, Chris Hill, S Hill, C Beatty; Specification and Testing of GNSS Vulnerabilities. Coordinates Magazine 2013
  7. Dixon, C.S., S Smith, A Hart, R. Keast, S Lithgow, A Grant, J Šafář, G Shaw, Chris Hill, S Hill, C Beatty; Specification and Testing of GNSS Vulnerabilities. ENC GNSS 2013. Vienna, Austria, 23-25 April 2013.

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