Jamming and spoofing
Contents: Jamming and spoofing
Jamming
You’re under a wide open sky and your smartphone is working perfectly but the GPS receiver just can’t get a fix. The weak GPS signals are easily jammed and that might be the problem. Here in the UK some military exercises deliberately jam GPS signals. ‘Denial of GPS’ in the Western Isles and other parts of Scotland for military exercises is not unusual.
GPS jamming during military exercise Joint Warrior
Hillwalkers urged use maps and not just GPS
GPS to be jammed in Scotland during Nato war games
However, the military jam signals in other parts of the country too.
The jammed area may extend for tens of kilometres around the exercise.
The jamming consists of random noise transmitted on the same frequencies used by GPS systems to overwhelm the weak signals from space. GPS receivers in a jammed area won’t be able to get a location fix as the satellite signals will be swamped by the jamming noise.
Ofcom is the UK governments regulatory body responsible for making sure the radio spectrum is effectively used. They say…
“The Ministry of Defence conducts occasional tests on military systems, which may result in some loss of service to civilian users of the Global Positioning System (GPS) including in-car navigation devices and networks which rely on GPS signals.”
The Ofcom website provides advance notifications for these military exercises. Currently they are found here or search the Ofcom website for ‘GPS jamming exercises’.
The notifications will explain where and when the exercise is happening and how widespread the jamming is likely to be. The higher you are, the more likely you are to be affected. In the example above you can see that if you’re up a hill you could be 40km away and have your GPS navigation spoilt.
Ofcom also warn that the notifications “may not cover all jamming exercises”.
Spoofing
This is a more sophisticated version of jamming. The spoofer transmits signals containing fake GPS timing and location data. GPS receivers near the spoofing transmitter can be tricked to report a location on the other side of the world.
Spoofing transmitters are cheap to buy and unlikely to be used for the worthiest of reasons. eg Drivers might use them to mask criminal activity they don’t want recorded by their vehicles onboard GPS tracker.
Spoofing is less likely to be a problem compared to jamming. I don’t suppose many of us will ever be affected, but never say never.