Methods and systems for orienting a mobile device to a vehicle's reference frame

1. A method of providing a quaternion for reference frame transformation, the method comprising:

(a) initiating a driving event in a vehicle having a vehicle reference frame;

(b) receiving, from a mobile device having a mobile device reference frame, mobile device data associated with a time stamp;

(c) determining, from the mobile device data, a first orientation of a gravity vector with respect to a first axis of the mobile device reference frame;

(d) determining, from the mobile device data, a second orientation of a magnetic direction with respect to a second axis of the mobile device reference frame;

(e) determining, using Global Positioning System (GPS) data provided by a GPS unit, a direction of travel for the vehicle with respect to the magnetic direction;

(f) determining a vertical inclination angle for the vehicle, wherein determining the vertical inclination angle for the vehicle comprises determining an altitude change and a distance change using the GPS data provided by the GPS unit;

(g) computing a quaternion that represents a rotation between the mobile device reference frame and the vehicle reference frame using the first orientation, the second orientation, the direction of travel and the vertical inclination angle for the vehicle;

(h) determining if the driving event is complete;

incrementing the time stamp and iterating steps (b), (c), (d), (e), (f), (g), and (h) if the driving event is not complete; and

providing the quaternion for reference frame transformation if the driving event is complete.

2. The method of claim 1 wherein the mobile device data is received in the mobile device reference frame.

3. The method of claim 2 wherein iterating steps (b), (c), (d), (e), (f), (g), and (h) produces a vector including a plurality of quaternions as a function of time.

4. The method of claim 3 further comprising using the vector to convert a string of the mobile device data in the mobile device reference frame into a string of data referenced to the vehicle reference frame.

5. The method of claim 2 further comprising utilizing the quaternion to transform the mobile device data in the mobile device reference frame into the vehicle reference frame.

6. The method of claim 1 further comprising:

obtaining motion data from the mobile device during the driving event;

orienting the obtained motion data to the vehicle reference frame using the quaternion; and

identifying a use of the mobile device by a driver during the driving event in response to:

determining that the mobile device has moved to the left with respect to the vehicle; and

determining that a front screen of the mobile device faces to the left with respect to the vehicle.

7. The method of claim 6 wherein determining that the front screen of the mobile device faces to the left with respect to the vehicle is performed after determining that the mobile device has moved to the left with respect to the vehicle.

8. The method of claim 6 wherein the motion data from the mobile device is obtained in the mobile device reference frame.

9. The method of claim 6 wherein the motion data includes accelerometer data.

10. The method of claim 6 wherein the motion data includes magnetometer data.

11. The method of claim 6 wherein the motion data is oriented to the vehicle reference frame by aligning a first axis of the mobile device with a gravity vector, aligning a second axis of the mobile device with a magnetic vector, and aligning the second axis to the direction of travel.

12. The method of claim 1 , wherein computing the quaternion comprises:

generating, from the first orientation of the gravity vector with respect to the first axis of the mobile device reference frame, a first quaternion that rotates the mobile device reference frame to align the first axis with the gravity vector;

generating, from the second orientation of the magnetic direction with respect to the second axis of the mobile device reference frame, a second quaternion that rotates the mobile device reference frame to align the second axis with the magnetic direction;

generating, from the direction of travel for the vehicle, a third quaternion that represents a rotation from the magnetic direction to the direction of travel for the vehicle; and

combining the first quaternion, the second quaternion, and the third quaternion into the quaternion.