Determining axis of rotation from gyroscope when initial orientation is variable

Question

An iPhone is held in front of you vertically (pitch is 90 degrees) with the screen either pointing toward your face, or with the screen pointed to one side of your face (so the iPhone is a sliver). It can also be somewhere inbetween. The iPhone then rotates 360 degrees about either the axis drawn from your nose to the iPhone, or from an axis drawn between your two eyes. How can you determine which axis the iPhone rotated around?

The gyroscope measurements are known at all times during the rotation.

Thanks for any help, or pointing me in the right direction!

Answer 1

Not sure if this is what you are looking for:

Have a look at the developer documentation, in the section called "Handling Rotation-Rate Data" you will find the angles to which refer the readings of the three axis of the gyroscope sensor.