Patent ID: 9068843
Filing Date: 2015-06-30
Classification: G01C,G06F,H04W

Abstract:
1. A computer-implemented method, comprising: determining a first predicted change of orientation of a device over time by compounding a product of one-half times a previous corrected orientation with first rotational rate data based on first gyroscope data from a three-axis gyroscope of the device; determining a first predicted orientation expressing an orientation of an Earth reference frame relative a first predicted frame of the device by adding the previous corrected orientation to a product of the first predicted change of orientation over time multiplied by a sampling rate of the three-axis gyroscope; determining a first predictive unit vector representing a first predicted direction of gravity based on compounding a conjugate of the previous corrected orientation with a gravity vector and with the previous corrected orientation; determining a first measured unit vector representing a first measured direction of gravity of the device based on first accelerometer data from a three-axis accelerometer of the device; determining a first cross-product of the first predictive unit vector and the first measured unit vector, the first cross-product resulting in a first cross-product vector that is perpendicular to both the first predicted direction of gravity and the first measured direction of gravity; determining a first angle corresponding to a difference between the first predicted direction of gravity and the first measured direction of gravity; determining a first correction comprising a rotation of the first predicted frame of the device around the first cross-product unit vector in a sensor frame of the device by the first angle times an accelerometer jitter offset constant that is greater than zero and less than or equal to one, the accelerometer jitter offset constant set based on noise characteristics of the three-axis accelerometer; and determining a first corrected orientation of the device based on compounding the first predicted orientation with the first correction, the first corrected orientation expressing the Earth reference frame relative to the sensor frame.