> spoofing

I don't understand how "spoof-to" works. If you have to mimic a satellite then isn't everyone going to get a different location? Unless you're tracking a specific target how can you intentionally spoof them to a desired location? I'd assume the best you could do is create a fixed offset.

> The military wants to go mostly inertial and is working on better inertial systems.

Given the drift rate this is an idea for munitions but exceptionally difficult to actually operate in a vehicle.

Clock bias.

Because the clocks internal to GNSS receivers are not that accurate, if they're not at the "targeted" location they'll see that all satellites are off by a given time offset, and think that their clock is just off by that much.

You mimic several satellites