WAAS/EGNOS does augmentation and surveillance. In this context, I’m of course talking about the surveillance part (which makes using RAIM unnecessary because the receiver can itself monitor the integrity of the signal). The question is if the surveillance mechanism can be spoofed predictably.
It will work if the jamming signal does not affect the signal received by the WAAS/EGNOS ground station 
This article about GPS spoofing from our shipping agent’s newsletter caught my eye this morning.
Spoofing would seem to be more of a PITA than mere jamming. Has anyone experienced it in an airplane?
I haven’t experienced it, but I saw a number of reports (though none of them in flight, either). For the time being, spoofing in wide geographic areas seems to be endemic to Russia. Also, what I heard about does not look like a continuous distortion of the map – it’s merely one fixed position being broadcast over a large area, which makes it easily discernible in flight.
How do you broadcast a fixed location? I thought GPS derived its location by the receiver receiving multiple satellites’ packets, each with a time stamp, and by correlating them it gets its location. So if you spoofed multiple satellites, the result would be that multiple receivers would compute different locations. I can see you could rig the signal generator to fool a specific receiver into computing a specific desired location.
What seems easier is spoofing some (multiple) satellites’ signals so that any receiver attempting to compute a location will get a shifted location.
I don’t know if this is related to GPS spoofing or jamming, but during two of my recent trips over the Baltic sea all of my GPS receivers died. iPad, Xperia phone and external PilotAware GPS receiver all died and came back online at the same time. During the second trip a military exercise was being conducted just north of my position and that might have been the reason.
Thankfully GPS was not required for my navigation as I could easily navigate visually and using VORs over the sea.
PS: 2 years ago I experienced the same phenomenon just South of Oslo.
If you broadcast from a single location, getting receivers to believe they are at one particular spot is the simplest thing one can do, and pretty much the only thing if there are many satellites in view
GPS in essence works by measuring signal timing / delay, and does so by using the relative time shift of the “pseudo-random code” sent by each satellite. When the receiver moves, and the distance to one satellite increases and to another one decreases, the time shift changes differently for both satellites, and the computed GPS position changes accordingly.
If you send a spoofed signal from one location, the relative time shift will remain the same, and hence the receiver will think it is still in the same position. The fact that the signals all shift together will be interpreted as drift of the internal clock.
To do anything more sophisticated, spoofing signals would need to be sent from multiple locations, and/or override the signals of one or more specific satellites in a way that they are not off too much and get knocked out of the solution
Peter wrote:
How do you broadcast a fixed location? I thought GPS derived its location by the receiver receiving multiple satellites’ packets, each with a time stamp, and by correlating them it gets its location. So if you spoofed multiple satellites, the result would be that multiple receivers would compute different locations.
Easy – you construct a superposition of all satellites’ signals the way they would arrive at your target location, and then transmit this mix from a single antenna, radiating enough power to completely drown out the true satellite signals. The receiver has no internal time-of-day clock, it derives time from the received satellite signals, but since the fake signals are already pre-correlated, the receivers at different points would calculate the same position but different time (depending on the propagation time from the spoofing transmitter).
Ha, Cobalt beat me to it…
I once experienced this going to Zagreb in the late 1990’s, the brace of MIG-21s behind me on the ILS, presumably did not rely on GPS.
http://www.wired.co.uk/article/black-sea-ship-hacking-russia
GPS jamming is very widespread. The political center of Cairo is constantly jammed, I always lose GPS there. ATC always switch from own navigation to vectoring in that area.
