A conventional compass does not work in a car because magnetic distortions in the vehicle renders the reading unusable. The distortions come from the metal cage you're sitting in, the electronic noise everywhere, your loudspeakers and so on. There are a zillion sources for distortions.
The Grenadier compass ring is stepper-controlled (you can hear it) and thus fed by some µC. I am almost sure the input comes from the GPS controller.
However, a GPS can only calculate a heading/direction when in move.
So I think that the compass stores the last direction value which came from the GPS upon shut down and reuses this value until it receives a new, valid direction value from the GPS. Because it takes a bit for the GPS to be completely "up and running", the steering angle might be used together with the driving velocity to continuously calculate the direction until the GPS is completely up.
So the Grenadier compass is likely a more sophisticated instrument than one might think. You can not easily replace it with some traditional compass. You can try it: put such a compass on your dashboard and when the car moves just look what it does. It's mostly nonsense.
The Grenadier compass ring is stepper-controlled (you can hear it) and thus fed by some µC. I am almost sure the input comes from the GPS controller.
However, a GPS can only calculate a heading/direction when in move.
So I think that the compass stores the last direction value which came from the GPS upon shut down and reuses this value until it receives a new, valid direction value from the GPS. Because it takes a bit for the GPS to be completely "up and running", the steering angle might be used together with the driving velocity to continuously calculate the direction until the GPS is completely up.
So the Grenadier compass is likely a more sophisticated instrument than one might think. You can not easily replace it with some traditional compass. You can try it: put such a compass on your dashboard and when the car moves just look what it does. It's mostly nonsense.
