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When you first get your iPhone, you might notice the calibration screen often. iOS builds calibration tables based on what it "learns" about its environment.

So each time you have to calibrate, you are helping the iPhone learn about what caused the interference.

Now, I've only seen this twice in my car. No other place! This is quite common though. And after I calibrated it twice, it doesn't get interference while in my car. Compass is dead on.
 
Why don't you do a control experiment? Drive out to the middle of a field, football field or whatever. Then try out your compass. If there is interference, then I have bad news for you...someone put metal and/or magnets in your body.

Either that or a magnetic personality.
 
I don't trust my compass.

I know for a fact that it's 90 degrees off. I can compare the compass on our boat with the one on my iPhone... way way off.
 
The compass app on mine usually asks me to wave the phone in a figure-8, but most of the time takes under 10 secs...usually a few secs. You must be waving it wrong.

-C

Sent from my iPhone 4.
Answered in first reply.
 
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