Do GPS blockers work?

August 24, 2011 12:44 PM

GPS blocker devices are widely sold. Do they really work?

There are times when I want to go dark. Given my situation, it is not unreasonable to be wary of someone planting a GPS tracking device in my car. I see GPS blockers sold all over the place, for not much money - and in a quick Internet search I find nothing that either confirms or denies that they work. I'd like to know what the hive's experiences with this have been. Thanks.

posted by reacheround to Technology (6 answers total)

you could bring a friend's gps into a shop and see if it works
posted by Ironmouth at 12:50 PM on August 24, 2011

I can't speak to any specific brand, but the technology to block GPS is pretty basic, and the military uses it all the time.

Basically GPS is just radio signals from satellites - the same ones that kids used to tune in to to hear the beeping from Sputnik on their short waves in the 50s. The satellites send a signal with the time and their location, and the GPS receiver needs 4 signals to triangulate a position (3 for location, the 4th for altitude).

All a blocker would have to do is send a signal on the same frequency, just sending noise instead of a readable signal. The noise drowns the satellite signal, and the GPS is "blocked".
posted by I am the Walrus at 12:51 PM on August 24, 2011 [2 favorites]

They do work but there can be significant unintended consequences, as detailed in this article. Note that they are illegal in the US.
posted by ChrisHartley at 1:03 PM on August 24, 2011

That New Scientist article was fact-checked and found to be misleading: Fact Check: Mysterious Outage Unleashes S.D. Chaos?.
posted by Mo Nickels at 1:15 PM on August 24, 2011

It is as Walrus said, it's quite simple to block GPS technically. Since the GPS signal is sent from satellites in low-earth orbit (a far and weak source), it is easily overwhelmed by a jammer near by. GPS operation is also very sensitive (the signal contains very accurate timing signal), thus it is vulnerable to noise and deliberate interference.

That said, it's illegal to operate (or own?) a GPS jammer. GPS is used in many places, and jamming it affects many vital services: E911 uses GPS to locate people for emergency service; the cell phone towers uses GPS to synchronize their clock; not to mention plane/boat navigation.

So, if you are just paranoid by being tracked in your car, perhaps a bug-sweeper (detecting radio emission) is what you want. Do NOT willy-nilly interfere with GPS because the consequence of this may be more disastrous (for many and for you) than whatever you may personally gain.
posted by curiousZ at 1:43 PM on August 24, 2011

This would be really irresponsible. Emergency vehicles like ambulances routinely use GPS to find an address. Due to the weakness of the GPS signal at ground level, GPS jammers tend to jam a much wider area than intended, so your jamming could easily put somebody's life in danger.
You could just inspect your vehicle for tracking devices, the presence of which seems very unlikely.
posted by w0mbat at 7:16 PM on August 24, 2011 [1 favorite]