Existing laws? Surely intentionally hacking a cars navigation system is a crime in most (all?) states. Analog would be that I can’t go around laying nails and thumbtacks on the highway.

Many different methods of hacking are illegal, and yet they still occur. Nails and thumbtacks less frequently.

That's like saying that "Gun Free" zones are the solution to preventing shootings. If the law is practically unenforceable, you need a different solution.

Spoofing GPS is already illegal, but that doesn't mean people cant do it.

Onboard computers can have compasses and a pretty good idea of how fast they're going. You could just be monitoring for any weird jumps or incongruences (eg. there is a road here, but it's at a different angle than the GPS signal indicates, the path recently followed doesn't match up with the map based on current GPS reading, ...) assuming you have good enough accuracy and can track it over time.

Seems like the spoofers could work around that and still do damage if they wanted to, by gradually shifting away from reality. The open-loop position estimate will never be perfect, so some margin would have to be designed into such a check, and that could be exploited. It would still be better than nothing though.

Yep, should work on those hundreds-of-miles-straight midwest roads ;)

Nitpicking but compasses are useless in a driving EV.

Why, the motor makes too much of a magnetic field? What if it corrected for the field it projects the motor to make at a given speed?

The display in pretty much all GPS units uses a compass to orient the little car/human thingie. I've never seen my phone map display be disoriented by accelerating in an EV.

Maybe they are using GPS bearing with gyro compensation?

Why is that?

Claims without explanation don't move the conversation forward much.

Oh, ye, the current gives strong magnetic fields.

YMMV but I've done IMU measurements in a EV and the compass course changed like 90 degrees from zero to full throttle. Was a low voltage 50V EV prototype though (higher currents).

To be fair I'm not too sure how sensitive compasses are in high voltage EVs.

A couple of years ago there was a headline about Israeli research into keeping track of movements without GPS, like in a cave. I wonder if these systems could keep track of the last mile or minute and compare various sources.

Correlating gps/glonass/galileo data to see if they all agree should be fairly effective, right?

It would raise the bar a little bit for spoofing, but not really change the set of people to whom the spoof attack is available.

Seems like that only makes it 3x harder.

How would you prevent replay attacks?