Patent ID: 9739635
Date: 2017-08-22
CPC Classifications: G01C

Claim:
1. A non-transitory computer readable storage medium comprising instructions that, when executed on a computing system of a person mounted portable device having a magnetic sensor for a compass and a gyro sensor, cause the computing system to at least: calculate a tracking path for the portable device by obtaining tracking data along the tracking path comprising a plurality of tracking points, the tracking data including gyro data and compass data associated with the portable device; transform the gyro data and the compass data into a navigation frame to compensate for tilt of the portable device; compute a compass heading based on the compass data and a gyro heading based on the gyro data in the navigation frame; determine a first drift based on a best fit line of a difference between the compass heading and the gyro heading in the navigation frame; estimate compass calibration error by determining a second drift comprising: estimate gyro calibration error by calculating a gyro heading drift based on the first drift and the second drift; update the gyro data and the compass data based on the estimated gyro calibration error; and correct at least a portion of the tracking path using the updated gyro data and compass data.