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The GPS constellation is rock solid, with unimaginable levels of sedurity.
It is tested by established stations scattered around the world constantly.
The weak spot is the hardware that uses GPS on the surface for navigation, as they can be individually subject to spoofing, and even total unavailability of service through jamming.
I’m thinking that the Air Canada plane that tried to land on a taxiway at SFO might have been tampered with in this same manner as the destroyers apparently were.
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That's encouraging... Coast Guard Stations, right?