A subtle form of navigation signal jamming, in the hands of terrorists or criminals, could affect GPS satellite navigation in a way that could disrupt all users, including aircraft operators, says the immediate past president of the UK Royal Institute of Navigation, Prof David Last.

Conventional area jamming of GPS is of more concern for mariners and terrestrial users than aviators, because aviation has retained alternative navigation systems, whereas the others have discarded them.

But a subtle, more targeted form of jamming that Last calls "spoofing" could go unnoticed by a crew. Spoofing, for example, could target the altitude information only for an aircraft carrying out a GPS required navigation performance or special category one approach.

Last says the list of potential "spoofers" includes terrorists, the "brighter end of the criminal fraternity", and hackers.

He says criminals could target GPS tracking systems on security vehicles carrying money or bullion and, because the spoofing would affect all GPS receivers within range, it could have an impact on aviation receivers if performed near an airport. And depending on the nature of the spoof, it might not be immediately noticeable to the crew, says Last.

Source: Flight International