Unjamming GPS – New technologies to secure satellite signals


The issues raised by jamming of signals from GPS have still to be debated, but with more and more applications making use of GNSS signals — including car insurance — technologists must work on the problem alongside lawmakers and enforcers, says Bob Cockshott

The dangers of our overreliance on the weak signals provided by Global Navigation Satellite Systems (GNSS) like GPS, and the proliferation of illegal jammers that can wipe them out is well established, threatening everything from navigation at sea to the algorithms that underpin modern banking and finance. And yet with GPS tracked car insurances, company vehicle tracking, criminal tagging and asset monitoring, GPS is being thrust upon us more and more.

New results unveiled last month by the Technology Strategy Board funded Sentinel project found up to 10 incidence of jammer use recorded each day at certain busy motorway locations in the UK, a significant increase in use in only the handful of year’s since we started monitoring our busiest roadsides for GPS interference.

It is this threat combined with that of solar storms further highlighted in last month’s Royal Academy of Engineering report, that has seen a community of technologists, policy makers and legal minds emerging with new ideas to keep us secure. Many of these new ideas were presented last month at GNSS Vulnerabilities 2013.

The first stage in countering this threat is to establish its true nature in the context of each person or organisation’s own operations and use of GNSS. The SENTINEL project mentioned above can now quickly deploy small test networks to organisations with critical infrastructure dependent on GNSS signals so they can quantify the problem for themselves.

If a threat is established there are a number of current protective technologies on offer and many more to come in the future. Some of these originate from the military domain where the threat of GPS jammers has been a source of innovation for many years. At the GNSS Vulnerabilities conference defence company Raytheon explained how the modernisation and miniaturisation of controlled reception patterns antennas (CRPA) technology could do help secure civil operations, particularly those of high critically such as in aircraft positioning and landing.

CRPA technology is considered to be the best proactive protection technique against GNSS interference. It consists of multiple antennas and an analysis box processing unit. The box looks for losses of signal and is able to attribute a location to a particular source of interference which it then isolates and ignores. Whilst previously far too expensive, this type of technology is now available at suitably reduced cost, size and power consumption for use in the civilian world.

And if you still can’t fully trust your GNSS signal – get a backup.

In the maritime world, where the threat of ships sailing virtually blind as a result of a major jamming event is a real one, the first protective steps are being taken right now. At the start of next March the General Lighthouse Authorities will unveil the first operational demonstration of a new type of jamming-proof receiver for the shipping industry. It takes advantage of  eLoran, a radio-based signal recently launched across the world’s busiest shipping lanes, near Dover. The receiver is the first in the world to automatically and seamlessly switch over to eLoran should the GNSS signal become interfered with.

With these technologies in place, the final step is to provide some form of assurance that you have successfully protected your GPS based systems against any reasonable threat. At the conference the STAVOG project unveiled the results of a yearlong project to develop state of art interference simulations using Spirent, a UK based simulator manufacturer. These mimic the various threats to GNSS signal covering both extreme solar weather and the latest illegal jamming devices available online. The consortium behind the project has announced that they will be making this service available for any GNSS users to test the security of their systems.

Whilst the technologies and engineering solutions are coming forward, these approaches must be combined with attempts to tackle the problem at source, whether that be greater public awareness of the dangers of operating these jamming devices or greater power to the authorities to identify and remove them from use. Taking the issue back one step further, we could also look at civil and commercial policies that lead otherwise law abiding members the public to buy illegal jammers in the first place.   

All these issues are to be debated but what is certain is there is no one solution that fits all. Instead it will require technologist and engineers to engage with law enforcers, politicians and the general public to find a workable answer that keeps us all on track and on time.

Bob Cockshott is Director of Position, Navigation and Timing at the ICT Knowledge Transfer Network and organiser of the GNSS Vulnerabilities conference