The use of a GPS jammer is illegal in the UK, as well as in the US and most European countries. It’s also illegal to sell such devices in the UK – with a maximum fine of £5,000 and forfeiture of stock.

According to Ofcom, the use of jamming equipment is an indictable offence under the Wireless Telegraphy Act 2006, and carries a maximum penalty of two years imprisonment and an unlimited fine.

A loophole in the law means that it is not illegal to buy or own them, so while Ofcom has closed down UK-based websites selling GPS jammers, it possible for the UK public to buy these devices from international sellers who sell them on auction sites for as low as £15. Their availability means that even though their use is illegal, they are becoming more common on Britain’s roads – with potentially disruptive consequences.

Serious Consequences of GPS Jammers

In August 2012, a GPS system for the blind landing of aeroplanes was being tested at Newark Airport in the United States. The system would regularly crash at the same time each day, and after much investigation the cause was traced to a GPS jammer used by a trucker driving on the nearby New Jersey Turnpike. He was using the jammer to mask his movements from his employers, who were using GPS trackers in their vehicles. The trucker was arrested and fined $32,000, although the authorities in the US have stated that they will consider pursuing more aggressive sanctions in the future.

Most obviously, the GPS jammers will interfere with the GPS signals in their immediate area. Depending on weather conditions and the power output of the device, this could create a bubble of interference with a radius of up to 300m.

In 2010 Professor David Last conducted an experiment  aboard the lighthouse tender THV Galatea. He wanted to find out the effect a GPS jammer would have on the ship’s state-of-the-art navigation systems. His findings were surprising.

THV Galatea
The instruments on the bridge of the THV Galatea went haywire when a GPS jammer was activated. Image credit Brian Burnell, Wikipedia

 

When the jammer was turned on, many of the ship’s systems shut down. Alarms sounded and the satellite positioning system crashed, as did the navigational backup gyrocompass and the radar system. Even the satellite communication system stopped working, since it needs GPS to calibrate its directional antenna. “The crew were well trained and briefed, so they knew what was going on,” said Professor Last, “but like us, they were surprised.”

There are over 1 billion GPS receivers estimated to be in use worldwide – but only about 10% of those use GPS for positioning. The rest of the devices only use the GPS network’s accurate timing system in order to synchronise their own systems. For this reason, GPS receivers can be critical in mobile phone towers, power grids and even cashpoint machines. Even a low power GPS blocker on a car dashboard has the ability to disrupt these systems if it passes close enough.

In addition to being hazardous to aviation and shipping navigation systems, GPS jammers can also hamper both navigation and communication for emergency and rescue services, and other critical infrastructure. Safety experts have brought up the scenario of shipping cargo hijackers using GPS jammers and blockers while crossing a busy shipping lane such as the the English channel, and the fatal consequences this might have.

The bottom line is that even the relatively low powered GPS jammers available online will disrupt GPS in a radius much greater than just your vehicle – and their signal will jam much more than just satnav systems.

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Who uses them and why?

GPS jammers are being increasingly used by car thieves aiming to avoid detection after a theft, since high value cars are often fitted with GPS trackers for security. There have also been reports of hijackers using jammers on trucks carrying valuable cargo to prevent the truck drivers from getting help and their managers from seeing them diverting from their normal routes.

But they are also increasingly being used by commercial drivers, who want to cover their tracks from their bosses. Vehicle tracking systems have made it possible for fleet managers to monitor their employees’ performances more effectively, to ensure that they’re driving safely and within the limits of the law, to help them with effective route planning, and ensure they work a safe number of hours.

The introduction of vehicle tracking systems can sometimes go down badly amongst some of the drivers who see it as an  invasion of privacy. Perhaps those who are used to taking the company vehicle for personal errands or private work while on company time. GPS jammers are also common among taxi drivers who like to pick up extra fare or two without their employers’ knowledge and pocket the money.

More dangerously, some commercial drivers could use these devices in order to avoid their time being clocked and circumvent laws on safe driving hours.

How exactly do these jammers and blockers work?

GPS (Global Positioning Systems) receivers require signals from 4 or more GPS satellites in order to get a fix. The satellites are in orbit around 12,000 miles above the surface of the earth, and the signal they send out is not very powerful since they rely on solar cells for their power. It’s about the same power output as a car headlight that covers half of the planet.

A relatively low powered jammer that broadcasts noise on the same frequencies will easily drown out such a weak signal – which is why the jammer’s effective range can be so high, even though it might be a relatively low powered signal.

When don’t Jammers work?

Each jamming device is different – but basic jammers will only operate on the frequency used by the GPS (Navstar) GNSS network. This means that navigation systems that can also use the Russian GLONASS network and the EU Galileo network can still function normally. In addition to this – many higher end vehicle trackers use cellphone network triangulation in order to get a faster fix, and will still be able to detect their position through these means.

Many vehicle trackers integrate with the CAN bus of the vehicle, and are connected to the vehicle’s power supply – sending data updates over the mobile phone network every few seconds. Jamming the GPS will not affect this transfer of data unless the GSM phone network is also jammed, so the perpetrator will soon be found out.

How widespread is their use?

In late 2011, a study was conducted using a network of covert listening stations in areas in the UK that had been experiencing unexplained distortions in their GPS receiving equipment. Among the organisations involved were the Ordnance Survey, Thatcham Security and the police. The study, set up by Chronos Technology, found that as many as 10 jamming incidents occurred each day in some areas, and suggested that there may be thousands of jammers in use nationwide.

Detecting and Stopping GPS Jammers and Blockers

There is an active campaign led by Brad Parkinson, who led the development of GPS, for the UK to introduce new legislation that will impose harsher penalties on people caught using GPS jammers and blockers. According to Parkinson, the new law should have the same severity as in Australia, which jails offenders for as long as 5 years and fine them for almost AUS$1 million.

The government, with the help of GPS technology researchers, are directing efforts to make it easier to catch people who use jammers and blockers. Chronos Technology, for instance, has developed a handheld radar that can detect and locate jammers. The radar is powerful enough to detect GPS jamming signals, no matter how weak they are, and can locate them even in multi-storey car parks.

Mr Parkinson is also leading the research into making GPS receivers less vulnerable to jammers and blockers. The military currently uses directional antennas to boost GPS signals, but these are too expensive to be used on a wide scale.

Alternatives to GPS technology are also being developed. Among these is eLORAN (enhanced LOng RAnge Navigation), which uses long wave radio signals emitted by land-based beacons, which are too powerful for ordinary jammers to block. The UK’s General Lighthouse Authorities was the first organisation in the world to start using this technology in 2013 in place of GPS.

In Summary

GPS jammers are illegal to use, they are disruptive and potentially dangerous for other road users, and those who use them are probably up to no good. Their use is potentially limited against high-end modern tracking systems, and the penalties for using them can be very harsh.

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Author - Nigel Vaughan

Nigel has over 10 years experience in digital marketing, and loves tech and all kinds of electronics. A keen cyclist and cycle-tourist, he has cycled through 25 countries worldwide.

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