In the past I've seen concerns about wide-scale GPS jamming (not just localized tampering), and also that the government might turn off the signal. I didn't pay that much attention since I'd never heard anything about it actually happening over a large area. Granted the military could reinstate selective availablity (SA), the 100 meter +/- error. And while the military has its own encryped super-accurate GPS signal (accessible only to special government receivers) they still needed the civilian signal in order to jump on to the secure signal; no way they would obliterate the civilian signal. So I blew off the whole GPS jamming/blackout 'threat'.

Well, a few things have changed.

1) Lyle Brotherton is the author of The Ultimate Navigation Manual. In the book he cites specific events where the GPS signal was purposely jammed by the government in Britain. They aren't always secretive about it either; he says the UK government posts warnings well ahead of time that the GPS signal will be weak or lost in certain geographic areas while they test their jamming protocols; here's an example. Lyle's book and website are excellent, by the way.

2) The US military has developed a modernized GPS capability in which the encrypted GPS signals are available directly to the government-only receivers, with no need for the civilian signal. Thus a significant barrier to blacking out the civilian signal is removed.

3) Wired Magazine has a report describing new GPS satellites whose signal is harder to jam, but it makes no mention of the military's government-only signal capability. At least the article has a really cool photo of a GPS satellite. At first I thought it was a candy machine from Willy Wonka's factory...

Europe is working on Galileo and Russia has GLONASS. I imagine that future nav devices will be able to use all three. However, it's hard to imagine that any combination of those systems would be especially difficult to jam or otherwise disable for a modern military.

GPS III satellites no longer have the Selective Availability feature.

No longer have the capability, or merely have the SA turned off?

I'm not privy to any inside information but I understand from what I read that the feature is not present on the latest satellites. According to an official US government statement at gps.gov

Localized jamming and spoofing by US, foreign and non-state actors is always possible, as has been recently reported in the online technical media.

There is a website which for us users might be useful: it's designed for pilots to check forecast gps disruptions prior to flight, but I imagine it might be of interest to ground-based gps users too.

http://www.raimprediction.net/

I expect that when the UK military plan gps jamming activities they coordinate with the CAA and relevant notams are issued to pilots well in advance. I would be surprised if was anything other than announced months ahead,

Jamming is super easy if you can physically locate a powerful radio transmitter where you need to jam. Just pump out lots of radio noise at the right frequency and no one can make out the relatively faint GPS signals above the clutter...

Come to think of it, spoofing the GPS signal shouldn't bee too hard, either. You know where the satellites will be at any given time, and you can calculate what the true signal will look like. Blocking the "true" signal with your spoofed version is a question of getting the right antenna and transmitter close enough to the area of interest.

I don't know any details (and anything interesting would probably be classified anyway), but I do know this is one area where the military has active research going on. I would also hazard a guess that systems less vulnerable to spoofing would be pretty high on the military Christmas wish list.

I seem to remember Dealextreme used to sell an L1 (1560-1580 Mhz)and L2 (1217-1237 Mhz) GPS Jammer i.e. for both the Military encrypted and Civilian Channels for about $30. Expanding the size of the jamming bubble just depends on the RF microwave power of the jamming antenna.

I have a Model:G30 Cell Phone and GPS Jammer which blocks 850-970Mhz CDMA/GSM 1560-1580Mhz L1 GPS and 1805-1930 Mhz DCS/PHS with 3 handy SMA microwave connectors which can be fed to tuned microwave Amplifiers.

It does a nice job at blocking GPS and older GSM 2 and 2.5 cellular phones . Once folks realise how easy it is to block GPS signals they begin to appreciate old school navigation.

L1 Spoofing is relativity easy as well as the GPS signal format is available on line.

http://www.navcen.uscg.gov/pubs/gps/sigspec/gpssps1.pdf

^ Agree it's not hard (or expensive!) to unselectively jam GPS. Note I don't address legality. It especially helps that the actual useful signal is below the noise floor to start with.

Interesting paper - not classified - on gps spoofing:
http://www.syssec.ethz.ch/research/ccs139-tippenhauer.pdf

^ Interesting. For those who don't read it: spoofing is not easy to do well, requires some significant means, and is also relatively easy to detect by anyone seriously looking for it.

BTW, I like that sat pic. Now *that's* a GPS satellite.

Jamming GPS, cellphone, and other signals is illegal in the US. I don't know what the legality is elsewhere.

Didn't Iran down the US spy drone with GPS spoofing? So it certainly is possible.

Spoofing GPS is not easy. Just knowing the signal format is only a beginning. Jamming is easy.

The University of Texas at Austin Radionavigation Laboratory recently demonstrated a spoof, takeover and redirection of a drone. A US military drone was captured intact by Iran last year using a spoof/redirection attack that induced the drone navigation system to land.

Spoofing currently requires only a few thousand dollars in equipment but needs considerable expertise. If the cost and skills needed come down and allow spoofing of civilian GPS from a distance of 100 feet or more by an unskilled attacker we may have a problem that dwarfs handheld lasers & airplanes.

This was an interesting incident considering the drone was also a high altitude 'Stealth' drone. So detection of the 'Stealth Drone' itself was even more sophisticated than the GPS 'Spoofing'. GPS 'Spoofing' might be more difficult than Differential GPS but probably no more sophisticated than implementing Real Time Kinematic RTK GPS based on phase measurements to get centimeter accuracy

As most Stealth aircraft will use AESA spread spectrum RADAR emitters i.e. for ground mapping imagery, I suspect that these radio signals were detected using an array of ground RADAR Warning Receivers RWR based on Software defined radio which digitises the microwave spectrum, which can give a directional information and when triangulated will pinpoint and track the AESA RADAR emitter. Its amazing what you can do with a Sony Playstation 3.

The same thing can be achieved using Networked PC Digital TV cards with firmware upgrades costing a few thousand dollars sometimes referred to as passive RADAR.

An aircraft intercept of the stealth drone with the GPS spoofing kit would then have gotten the stealth drone to follow it (follow me mode) back down to its air field.

GPS spoofing is actually an important defense area. i.e. A JDAM bomb could be redirected to behind the lines of the military who dropped it or at the very least missing its intended GPS coordinates.

The cost of this type of electronic equipment is dropping like a stone, take for example the Chinese made Tecsun PL360 radio receiver (around $45) based on the si4734 DSP chip

http://www.silabs.com/products/audiovideo/amfmreceivers/Pages/Si473435.aspx

Yes a complete digital signal Intermediate Frequency baseband processor for SW,MW,LW and Stereo FM Digital Radio Reciever!

I think there's more to that drone spoofing story. Not that I don't believe what we're told... If it was so easy it would have been a lot more than one drone by now. Or maybe it has been... It's just a drone anyway, they expect to lose them. I'm disappointed they don't have a James Bond-style "car alarm" setup, my drones would.

Speaking more generally now. What I got out of that spoofing doc linked to above was that a single spoofing source would not be enough. A modern GPS receiver should quickly ignore it. There could however be a minute or two until the receiver rejects that source, and that may be enough for the nefarious deed. Multiple signal sources *in the proper geometric locations* would normally be required.

Back to the drone: they apparently didn't have to do that, and it responded to its confusion by landing. I wonder if the Iranians made the landing place look fairly like the base where the drone would have normally landed? I thought there was always people behind the drones' control who could over-ride their autonomy.

That was a military drone presumably using an authenticated signal; it wasn't easy. There's no evidence is was the Iranians who did the spoof either.


They don't expect to lose them intact and undamaged, ready for enemy evaluation and reverse engineering to find weaknesses.


A single antenna suffices to spoof civilian GPS. Anything large enough for two GPS receivers could detect simple spoofing by comparing position solutions and known receiver separations.

A diligent GPS receiver might detect and reject a clumsy spoof but not a careful spoof takeover.


Not locations: GPS is all about *timing*. The signal sources can be anywhere you want as long as the signals arrive at the receiver with the right timing relative to each other.

With an authenticated GPS signal, where you can't change the satellite position data in the signal, you can jam the signals and send a delayed copy to the GPS receiver, tinkering with the relative timing of each satellite's signal so that the receiver solves for the position you want. It's tough to do, but apparently not tough enough.


The drones will autonomously return to base in the event of loss of command signal. A pilot is not needed.

The attack apparently jammed the command signal and then spoofed the GPS receiver so that when the drone tried to fly back to base it was really just flying in circles in Iranian airspace, and when the drone thought it was landing at home it was in fact spoofed to land at an Iranian airbase.

The Radionavigation Lab result is noteworthy as it was an entirely civilian effort by one professor and fewer than half-a-dozen students.

I would think you could _*calculate*_ what the signal including the delay as percieved by the GPS receiver should look like at any given time, in any given location. In principle, all the information is public available.



Just demonstrates my point: GPS is an open protocol, free for all to read and understand. Anyone with the proper skills in mathematics and engineering (and a little ingenuity) can get the information they need to develop spoofers and jammers.

Selective jamming of signals are indeed still a remaining issues to settle with further development of jamming system.

wireless jamming

Wow, within ONE minute of approving this member they posted spam from China. Amazing, since the spammer had been waiting for approval for almost a day.
-Blast

The newest Garmins have both US and russian satellite capability. Increases their usefulness and accuracy, too.

I think I read somewhere that the military is looking at creating non-GPS jam-proof navigation technology that involves a chip that contains multiple super accurate accelerometers. When the chip is manufactured it "knows" its current location, then by tracking acceleration in multiple directions it can calculate speed and direction ... constantly knowing where it is ... and even knowing relative position. Pretty cool idea.

I doubt that the US Govt would block GPS for all users across the country. but I am sure they would consider shutting it down at critical targets locations to protect things like the White House & Pentagon. That's logical. But they would need to know that an imminent threat exists ... that's their main headache.

Pete2