Naked Scientists Podcast

Naked Scientists episode

Wed, 5th Jun 2013

Can GPS systems be Spoofed?

GPS satellite (c) NASA

The science of satellite navigation and how it can be fooled or "spoofed", a new system to pinpoint a person within a building to within a metre, and how GPS signals can probe and track volcanic dust clouds. Plus, news of what nuclear bomb tests have revealed about the brain, why volcanoes might cause Parkinsonism, HPV and oral cancer and why we comfort-eat high fat foods when we get depressed...

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In this edition of Naked Scientists

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  • 12:30 - Planet caught in the act of forming

    The Atacama Large Millimetre Array has caught an image of what may be a planet in the process of forming.

  • 15:56 - What's in a name?

    Parents are subconsciously selecting names that linguistically portray bigger and stronger for boys, and more petite for girls...

  • 51:55 - How high can a mountain be?

    So I am just wondering- how high could a mountain on Earth be? The Olympus volcano on Mars is about 20 km high. But could a peak on Earth ever reach this height? And if not, why?



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As well as the primary GPS application of providing geographic location, GPS can be used in a secondary application of providing an accurate time reference. This is used in modern cellular phone networks to synchronise multiple transmitters covering overlapping areas to within 1 microsecond.

There have been instances reported where a GPS satellite has been accidentally left in "maintenance" mode, broadcasting an incorrect time, and upsetting synchronisation on telecommunications networks.
Presumably, the same thing could occur if the satellite were transmitting an incorrect orbital location.
Fortunately, this should not happen very often, this is not under the control of an individual user who may want to spoof the system, and the discrepancy should be easily detectable as inconsistent signals would be received from the other 3-6 satellites which are usually visible from a single location. evan_au, Thu, 6th Jun 2013

GPS is commonly used to lock SPGs (Sync Pulse Generators - the device used to lock all of the equipment in television facilities together) for accurate timecode.

Since you need to receive a signal from at least four satellites to determine your location (one signal puts you anywhere on the surface of a sphere, two signals put you on a big circle, three narrows that down to two intersects and the forth signal determines which one is you) and due to weak signals being acquired and lost often most GPS receivers will hold onto seven birds at once (you can typically "see" nine or ten satellites from sea level).
So - it would be easy to stop a receiver's ability to determine position by overloading it's (very sensitive) 1.5Ghz receiver, but to inject data into many carriers to spoof a location would be very hard. Don't know if it's ever been done? FunkyWorm, Fri, 7th Jun 2013

There has been spam on this forum, (since removed), to sell GPS jamming devices.
The sales-pitch was superficially aimed at the paranoid, but in reality the buyers must be up-to no-good. RD, Fri, 7th Jun 2013

Some GPS applications can be spoofed. There was a discussion of this on a recent CBC podcast called "Spark"

It can be used in the rental car and truck applications that track the vehicle's speed. You spoof the signal and mess with the timing.

It is very cumbersome now, but in time.

Incidentally, It is said that you can make a good piece of change selling phony "radar detectors" out of the back of your car to fools.  When the sucker goes to the police to complain, they aren't interested in helping a fool who was trying to spoof their radar speed traps.

However the jails ARE full of hucksters who thought their scam was foolproof. Pecos_Bill, Sat, 8th Jun 2013

There has been spam on this forum, (since removed), to sell GPS jamming devices.
The sales-pitch was superficially aimed at the paranoid, but in reality the buyers must be up-to no-good.

The family of greedy suckers is an ancient lineage. Pecos_Bill, Sat, 8th Jun 2013

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