How can I detect if an iPhone is rotating while being face up in a table?

Question

Is there a way to detect if an iphone lying down in a table face up is rotating?. I do realize that this kind of movement is not reported by the accelerometer and neither is it reported to the - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation method.

Is there a way to detect angle variations for the phone rotating this way?. Thank you.

Answer 1

The gravity vector will be constant as it rotates on a flat table so you won't see anything on the accelerometers. You could follow compass heading changes to detect this rotation but only on an iPhone 3G S. See the CLLocationManager for details, look at the heading methods.

EDIT - With an iPhone 4 you can detect the rotation using the gyros. There is a new class in iOS 4 called CMMotionManager for getting rotation rate from the gyros.