By Chris Vallance
BBC News
The illegal use of Global Positioning System (GPS) jammers in the UK has been revealed in a groundbreaking study.
GPS jammers are believed to be mostly used by people driving vehicles fitted with tracking devices in order to mask their whereabouts.
In one location the Sentinel study recorded over 60 GPS jamming incidents in 6 months.
The research follows concern that jammers could interfere with critical systems which rely on GPS.
The team behind the research believe it is the first study of its kind in the UK.
Its findings will be presented at the GNSS Vulnerability 2012: Present Danger, Future Threats conference held at the National Physical Laboratory on Wednesday.
Road watch
The Sentinel research project used 20 roadside monitors to detect jammer use.
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The next step is to develop the system further so that it can be used for enforcement”
Bob Cockshott
ICT Knowledge Transfer Network
"We think it's the only system of its kind in the world," Bob Cockshott of the ICT Knowledge Transfer Network and organiser of the conference told the BBC.
The sensors recorded every time a vehicle with a jammer passed by.
"We believe there's between 50 and 450 occurrences in the UK everyday," said Charles Curry of Chronos Technology, the company leading the project, though he stressed that they were still analysing the data.
He told the BBC that evidence from the project suggested that most jammers were small portable devices with an area of effect of between 200m and 300m.
The project received £1.5m funding from the Technology Strategy Board and involved a number of partners including the Association of Chief Police Officers (ACPO).
Mr Curry said the research had also resulted in the detection and confiscation by the police of one jammer.
"We detected a pattern and they [the police] were able to go and sit and wait," he said.
Mr Curry said the research was also able to establish that jammers were responsible for interference experienced by Ordnance Survey equipment.
GPS jammers are widely available online, one reason Mr Cockshott believes the law around jammers needs tightening.
He thinks the Sentinel project should now work towards developing systems that will help catch those using jammers.
"The next step is to develop the system further so that it can be used for enforcement, so that you can detect a jammer in use and then relate it to the driver that's using it," he said.
Low watt
Logistics and other companies often install GPS trackers so they can follow the movements of vehicles.
They are also used so vehicles carrying valuable loads can be tracked.
Researchers believe most GPS jammers are used to stop these devices working.
"A GPS satellite emits no more power than a car headlight, and with that it has to illuminate half the earth's surface," Professor David Last, a past president of the Royal Institute of Navigation, told the BBC.
"A very, very low power jammer that broadcasts on the same radio frequency as the GPS will drown it out.
"Most of them are used by people who don't want their vehicles to be tracked," he said.
But the jamming technology can cause problems for other safety critical systems using GPS.
In mobile phone and power networks GPS satellite signals are sometimes used as a source of accurate timing information.
GPS is even used to provide accurate time information for some computerised transactions in financial markets.
And other GPS navigation devices used by ships and light aircraft could also be affected by jammers.
In 2009 Newark airport in the US found some of its GPS based systems were suffering repeated interference.
The problem was eventually traced back to a truck driver using a GPS jammer.
