Validating calibrated magnetometer data

摘要

Implementations are disclosed for validating data retrieved from a calibration database. In some implementations, calibrated magnetometer data for a magnetometer of a mobile device is retrieved from a calibration database and validated by data from another positioning system, such as course or heading data provided by a satellite-based positioning system. In some implementations, one or more context keys are used to retrieve magnetometer calibration data from a calibration database that is valid for a particular context of the mobile device, such as when the mobile device is mounted in a vehicle. In some implementations, currently retrieved calibration data is compared with previously retrieved calibration data to determine if the currently retrieved calibration data is valid.

主权项

1. A method comprising:
receiving a reading from a magnetometer of a mobile device; selecting a cluster from a plurality of clusters of bias offsets generated from previously-calibrated readings, wherein the selected cluster has a representative bias offset, a mean of magnitudes in the selected cluster, and a magnitude threshold; estimating an external magnetic field based on the reading and the representative bias offset for the selected cluster; determining whether a magnitude of the estimated external field is within a magnitude range defined by the mean magnitude and the mean magnitude plus the magnitude threshold; determining a gravitational vector; determining an inclination angle between the gravitational vector and the estimated magnetic field; determining whether the inclination angle is within an angle range defined by a mean inclination angle for the selected cluster and the mean angle plus an angle threshold; determining the magnitude of the estimated external field matches the magnitude range and the inclination angle matches the angle range; determining a first heading for the mobile device using the estimated external field; comparing the first heading with a second heading obtained from data provided by a location processor of the mobile device; and validating the first heading in response to the comparing,where the method is performed by one or more hardware processors.