I suspect the specific implementation here uses "carrier-phase RTK" which means the recievers are locking into the pure sinusoid of the carrier frequency to get

I suspect the specific implementation here uses "carrier-phase RTK" which means the recievers are locking into the pure sinusoid of the carrier frequency to get sub-centimeter positioning accuracy. It's mind blowing that this works at all, given that it really isn't how the GPS system was designed to be used.