this post was submitted on 23 Nov 2023
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GPS relies on timing - very precise timing - and signed signals. It might be that GPS units ignore that the signal should be signed, but the (picosecond) timing basically defines an objects' position in space. A picosecond makes a difference of a few centimeters.
Now, modern planes don't primarily rely on GPS. They have gyroscopes. But as gyroscopes lose precision over the duration of the flight, they cross-reference with GPS to fix this loss of precision. But for that, the measured GPS location must be close enough to the gyroscope-based location, or the GPS result is discarded as erroneous. So one needs not only to spoof any GPS signal, it must be close enough to the actual position, and then slowly move the target over.
BTW, the villains in the movie "Tomorrow never dies" use a different approach. They influence the GPS satellites directly, which is a totally different thing, and if Iran did attempt that, I think the US would react differently and ... more directly.
Wow this is so cool!! I did know it was timing based and needed to be precise, but this is so crazy! And to think we've gotten so good at making these precise timing circuits to just add them to all phones like it's nothing! This is really cool! And the part about spoofing GPS in planes, that is even crazier how can anyone accomplish that is beyond me it's pretty much magic at this point that's so cool!!
In the cell phone there are specialized chips that "just" read the signal. They use some interesting tricks to catch the timing right, but can't be used to produce such a signal. The satellite "just" sends a signal with it's own position and the timecode (based on it's own atomic clock). And those nanoseconds and picoseconds of difference when the signals from different satellites arrive determine the distance to those satellites, and together with their position, one can calculate the receivers location.