GPS jammers can also disrupt many communication systems, including the Tetra Airwave system used by emergency services. It transfers only one thousandth of the phone's charge. Jammers are readily available from Internet sources and cost only a few dozen pounds. Their impact on GPS-based security systems is severe.

　　They use them to disrupt tracking systems, thereby stealing vehicles and their valuable content. Jammer: A low-power radio transmitter that can overwhelm GPS reception at a range of tens of meters. This particular model also interferes with the mobile phone band. It blocks the data channel of any tracking system and disables mobile devices that can be used to call for assistance or track themselves using cell site analysis.

　　Nearby jammers can easily deafen a vehicle's sat navigator because it's hard for them to hear these tiny signals. GPS jammer technology is developing rapidly.

　　GPS, Galileo, Chinese, Japanese and Russian satellite navigation systems and their enhancements all use essentially the same technology and the same frequency bands. Therefore, switching from GPS to other GPS does not prevent interference.

　　If deployed correctly, it could affect the GPS of an entire city. This signal cellphone jammer would beat GPS-based road user pricing systems; and jammers ten times more powerful than those on the market today.

　　Even more serious than jammers are civilian GPS spoofers, which have been shown recently. Spoofing is sending fake GPS signals; the receiver locks on to them, and the spoofer takes control of the receiver. Fraudsters will allow criminals to hijack and divert the vehicle, while the tracking system shows it's still following its planned route, so no alarms will sound. Vehicles will also be able to avoid a purely GNSS-based road user pricing system.

　　There is no evidence yet that criminals have access to cheaters. But there are already low-cost GPS generators with programmable scenarios that can use Google Earth to input trajectories. So deception is not far off.

　　What are the options for mitigating interference and deception? Improve its technology to detect jammers and try to legally ban their sale and use. Of course, all radio systems are interferable - it's a matter of degree. But these two are harder to jam than GPS and don't draw people's attention.