How to detect abnormal magnetic field/orientation readings and recalibrate orientation sensor (compass reset)?

We are trying to develop an app that uses compass information, and facing a similar problem on the Droid Incredible [http://www.youtube.com/watch?v=qSDpHksACRc][at time-2:02].

my prob is similar to the link:http://androidforums.com/incredible-support-troubleshooting/73860-compass-calibration.html

** I have tested my app with nexus one also and its working fine in it. The only problem is Droid incredible. **

I do开发者_JS百科 not think repeatedly doing a factory reset will be a good idea for users. Ideally we would like to detect the abnormal magnetic field and ask the user to reset just the compass.

Can you please suggest how we can detect the abnormal magnetic field through code and trigger the compass reset?

Thanks