Minor point, but GPS isn't run by the US Army. It's run by the US Air Force.

You might want to add the link to the Virginia Tech News article on this research, which is at http://www.vtnews.vt.edu/story.php?relyear=2008&itemno=578 (but then, I guess I've just added it, though it would be more visible in the body of your column).

In my military experience, inertial navigation systems (INS) are unreliable and pilots have quickly learnt the GPS is 'always' right and so ignore them. 
What about the bombs and missiles that rely on GPS. Well at least the Americans would be able to have a new excuse why their ordance hit the wrong target.

Thanks to the commenter(s) explaining the suitcase sends out 5 fake signals, but nevertheless, since the US army runs the GPS system, and it's very obvious a hostile act (as well as a federal crime) to do such a thing as described, I can tell you I would not want to be the one standing there with that suitcase, although I suppose you could plant it somewhere with a delayed activation, but that still leaves the crosschecks planes do with other sources and telemetry.
Also didn't the GPS system take that into account? don't I recall there was some encryption involved, and that there was higher precision for those allowed?
I guess it's time to hit wikipedia if I want to know.

The signal from the spoofer device impersonates a whole handful of satellites, not just one. Most, if not all, GPS systems have no way to verify the direction the signal comes from. So, the spoofer sends fake signals from all possible satellites at once, with time delay offsets for each fake satellite that are just enough to convince the GPS unit of the spoofed course.

Since the briefaces is over 1000x closer to the GPS receiver than the actual satellites, its signal will override the real GPS signals.

then send out 5 fake signals

Anybody that ever used a GPS system in his/her car knows it demands a fix on a number of satellites before it deems the location info reliable, and that's a cheap car system, I assume a plane has even higher demands, as well as crosschecks.
So I don't see how 1 fake transmitter would do much damage, and I'm sure the army will be on such a suitcase in minutes and have a nice chat with the one carrying it, or a 500 pound package delivered if that's not possible.


There would be a simple voting system, where if one "satellite" (the spoofer) doesn't agree with the 5-7 other satellites the receiver is locked on, it gets tossed out.

Too bad this is all sensational journalism and you can bring down any commercial aircraft by falsifying the GPS signal because no airliners uses GPS as the only source of navigation.

Instead aircrafts navigation system constantly cross-check their position using conventional VOR-DME fixes, their own build-in inertial reference system (IRS/INS) and on top of it the GPS signal received.

The IRS, which has no outside connections, is precise enough to fly for 12-16 hours straight and still be able to determine the exact position within a quarter mile if no VOR-DME fixes are possible within that time period.

Also, GPS approaches are still not certified for the only means of performing a approach and landing within commercial operations and won't be for another few years, so no, a faked GPS signal won't bring any airliners down, not now and not in 10 years.

Wasn't there a Bond movie about this?

was this copied from James Bond?