Methods and systems for aligning a mobile device to a vehicle

1. A method of determining vehicle acceleration information with a mobile device disposed in a vehicle, the method comprising:

operating at least one sensor of the mobile device to obtain a plurality of movement measurements;

calculating, based on input from the at least one sensor of the mobile device, a plurality of gravity vectors, each of the plurality of gravity vectors being associated with at least two movement measurements of the plurality of movement measurements;

generating, with a vector analyzer of the mobile device, a gravity angle difference and a gravity magnitude difference associated with at least one movement measurement in which the mobile device was moving in the vehicle of the at least two movement measurements, and determining that the gravity angle difference is above a first threshold and that the gravity magnitude difference is above a second threshold;

removing the at least one movement measurement from the plurality of movement measurements using the plurality of gravity vectors to provide a set of remaining movement measurements of the mobile device; and

determining an acceleration measurement for the vehicle using the remaining movement measurements of the mobile device.

2. The method of claim 1 , wherein at least one of the plurality of gravity vectors is associated with an accelerometer measurement from the mobile device.

3. The method of claim 1 , wherein at least one of the plurality of gravity vectors is associated with a gyroscope measurement from the mobile device.

4. The method of claim 1 , wherein determining a plurality of gravity vectors comprises:

determining a first and second gravity vector over a time span;

determining that a change between the first and second gravity vectors over the time span is above a threshold; and

wherein removing a movement measurement from the plurality of movement measurements includes removing a movement measurement associated with the time span.

5. The method of claim 1 , further comprising, determining at least one gravity vector using quaternions.

6. The method of claim 1 , wherein determining the acceleration measurement for the vehicle using the remaining movement measurements comprises:

applying principle component analysis to the remaining movement measurements to identify longitudinal acceleration in a direction of travel of the vehicle, lateral acceleration perpendicular to the direction of travel of the vehicle, and vertical acceleration.

7. The method of claim 6 , wherein the vertical acceleration is identified by correlating a first acceleration component onto a gravity vector, wherein the lateral acceleration is identified by correlating a second acceleration component with a rotation rate around the gravity vector, and wherein a third acceleration component is identified as the longitudinal acceleration after identifying the vertical acceleration and the lateral acceleration.

8. The method of claim 6 , wherein determining the acceleration measurement for the vehicle using the remaining movement measurements further comprises:

calculating a first mean of the longitudinal acceleration over the remaining movement measurements;

removing the first mean from the longitudinal acceleration of the remaining movement measurements to generate a remaining longitudinal acceleration;

calculating a second mean of the lateral acceleration over the remaining movement measurements;

removing the second mean from the lateral acceleration of the remaining movement measurements to generate a remaining lateral acceleration;

calculating a third mean of the vertical acceleration over the remaining movement measurements; and

removing the third mean from the vertical acceleration of the remaining movement measurements to generate a remaining vertical acceleration.

9. The method of claim 8 , wherein determining the acceleration measurement for the vehicle using the remaining movement measurements further comprises:

determining a covariance matrix using the remaining longitudinal acceleration, the remaining lateral acceleration, and the remaining vertical acceleration;

identifying three largest eigenvalues from the covariance matrix;

identifying three eigenvectors corresponding to the three largest eigenvalues, wherein the three eigenvectors correspond to the acceleration measurement.

10. The method of claim 6 , wherein determining the acceleration measurement for the vehicle using the remaining movement measurements comprises:

determining a sign of the longitudinal acceleration.

11. A system for determining vehicle acceleration information with a mobile device disposed in a vehicle, the system comprising:

a processor;

a memory, having instructions stored thereon, that, when executed by the processor, cause the processor to perform operations, the operations comprising:

operating at least one sensor of the mobile device to obtain a plurality of movement measurements;

calculating, based on input from the at least one sensor of the mobile device, a plurality of gravity vectors, each of the plurality of gravity vectors being associated with at least two movement measurements of the plurality of movement measurements;

generating, with a vector analyzer of the mobile device, a gravity angle difference and a gravity magnitude difference associated with at least one movement measurement in which the mobile device was moving in the vehicle of the at least two movement measurements, and determining that the gravity angle difference is above a first threshold and that the gravity magnitude difference is above a second threshold;

removing the at least one movement measurement from the plurality of movement measurements using the plurality of gravity vectors to provide a set of remaining movement measurements of the mobile device; and

determining an acceleration measurement for the vehicle using the remaining movement measurements of the mobile device.

12. The system of claim 11 , wherein at least one of the plurality of gravity vectors is associated with an accelerometer measurement from the mobile device.

13. The system of claim 11 , wherein at least one of the plurality of gravity vectors is associated with a gyroscope measurement from the mobile device.

14. The system of claim 11 , wherein determining a plurality of gravity vectors comprises:

determining a first and second gravity vector over a time span;

determining that a change between the first and second gravity vectors over the time span is above a threshold; and

wherein removing a movement measurement from the plurality of movement measurements includes removing a movement measurement associated with the time span.

15. The system of claim 11 , further comprising, determining at least one gravity vector using quaternions.

16. A non-transitory computer readable storage medium having instructions stored thereon, that, when executed by a processor, cause the processor to perform operations comprising:

operating at least one sensor of a mobile device disposed in a vehicle to obtain a plurality of movement measurements;

calculating, based on input from the at least one sensor of the mobile device, a plurality of gravity vectors, each of the plurality of gravity vectors being associated with at least two movement measurements of the plurality of movement measurements;

generating, with a vector analyzer of the mobile device, a gravity angle difference and a gravity magnitude difference associated with at least one movement measurement in which the mobile device was moving in the vehicle of the at least two movement measurements, and determining that the gravity angle difference is above a first threshold and that the gravity magnitude difference is above a second threshold;

removing the at least one movement measurement from the plurality of movement measurements using the plurality of gravity vectors to provide a set of remaining movement measurements of the mobile device; and

determining an acceleration measurement for the vehicle using the remaining movement measurements of the mobile device.

17. The non-transitory computer readable storage medium of claim 16 , wherein at least one of the plurality of gravity vectors is associated with an accelerometer measurement from the mobile device.

18. The non-transitory computer readable storage medium of claim 16 , wherein at least one of the plurality of gravity vectors is associated with a gyroscope measurement from the mobile device.

19. The non-transitory computer readable storage medium of claim 16 , wherein determining a plurality of gravity vectors comprises:

determining a first and second gravity vector over a time span;

determining that a change between the first and second gravity vectors over the time span is above a threshold; and

wherein removing a movement measurement from the plurality of movement measurements includes removing a movement measurement associated with the time span.

20. The non-transitory computer readable storage medium of claim 16 , further comprising, determining at least one gravity vector using quaternions.