Is it possible to calibrate a compass so that it reads accurately in a car? I've been trying, unsuccessfully, to do so for the last 15 or 20 minutes. I know that the engine and all the electrical systems in the car will affect the compass. My question is, is this something that is impossible or simply difficult?

Are there compasses that are designed specifically for use within a car?

This is the compass:

I'm not really sure exactly what you're asking. But if you are sitting in your car and want to know how accurate the compass is, what you do is this:

Hang a weight by a string from your rearview mirror. The string will then be exactly up and down, pointed towards the center of the earth.
At exactly chatzot [today it was at 12:10 EST in NYC], look at the shadow that the string casts. That shadow will be exactly north-south. Now compare that to which direction the compass is pointing as north.

Your compass seems to be working fine. It's correctly pointing south east from my monitor towards my face.

Yes. They look something like this:

Thank you for your response. I know the approximate north direction and that is not my concern. What is my concern is that the compass is inaccurate when used inside the car (probably because of the electronic systems within which mess with its electromagnetic field or something). I cannot calibrate it because when I have it set to read accurately in a northerly direction, it will read inaccurately (and I don't mean slightly) in other directions. I want to know if anyone who has experience with compasses in general, automobile compasses in particular, or a strong knowledge of physics or automobiles can help me with this issue.



Actually, a GPS isn't entirely reliable for use as a compass. I borrowed my parents to use while calibrating the compass and it only recognizes when the car is actually driving in a specific direction. It was not sensitive enough to point to north when I merely turned the car in different directions.

Fine. Well then I'll bet you didn't think of this: Step out of your car with the compass and walk a good fifty feet away from any magnetic sources (besides Earth), and note "true" north. Then take it back into the car and see where the compass indicates north to be. Voila, you have your calibration adjustment.

I can do that. However, the compass will not indicate North when I return the compass to the car. And if I adjust it to indicate North and then turn to face East, it will not be accurate but may instead indicate anything from North to Southeast to West.