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For GPS precision is much more important than accuracy.

Precision vs. accuracy of what measurement?

For GPS to work at all, you need very accurate knowledge of the offset between each satellite's signal.

The only way I can think of to have precision but not accuracy is if you design a system where there's a buffer between the antenna and the signal processing and you don't know how long the buffer is. Is a design like that a practical concern?

They're saying that as a receiver of GPS signals, it doesn't matter if your clock is out of sync with everyone else's clocks, as long as it measures the length of a nanosecond accurately.

But GPS gives you a clock signal.

Of UTC. Theoretically GPS can work out of sync with respect to UTC as long as all satellites are in sync among themselves.

Oh, you're talking about a theoretical situation where the GPS satellites are reprogrammed to use a different synchronization source? Personally I'd still call that highly accurate, but to a different time standard. But I see where you're coming from.

With specialized GPS receivers, about +/-2ns. Closer to 40ns with commercial receivers.

statum-1 time server