Improve the estimation of the direction of movement

[fzampella-huawei]

Improve the estimation of the direction of movement.

To obtain the direction of movement, we need the orientation of the phone that can come from:

• The phone rotation vector
• Game rotation vector
• External estimation of the orientation from initial orientation, gyroscope, accelerometer and magnetometer

The estimation of the direction of movement from the orientation and IMU signals can be obtained from:

• Opposite the direction of the screen (-Z axis projection)
• Projection of an axis given the holding mode
• Estimation of the direction of the acceleration/rotations
• Horizontal accelerations

[fzampella-huawei]

Branch "4-improve-the-estimation-of-the-direction-of-movement" modified the orientation of the app to use only the rotation vector, this limits the control of the orientation but provides a much more stable orientation. I have observed that if the device starts a "cold" data collection (without previously calibrating the magnetometer and gyro), the initial orientation is wrong, but after a few turns the orientation is "corrected", however the previous orientation was incorrectly accumulated.

Make sure to calibrate the orientation before a data collection doing the following:

• Start a data collection session to initialize the sensors
• Rotate the phone in an 8 shape
• Keep the phone static in a flat surface for a few seconds
• Discard the data collection session

I recommend to offer other orientation estimation methods in the app, with the possibility of recalculating the orientation with another method in the correction mode (future work)