Methods for improved heading estimation
First 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;
sorting the compass data into bins based on compass angles associated with the compass data;
determining, for each bin, a weighted best fit line based on a compass reliability; and
determining an average slope of the weighted best fit lines of the gyro data subtracted from the compass data in each bin;
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.
1 Assignment
0 Petitions
Accused Products
Abstract
Methods for calibrating a body-worn magnetic sensor by spinning the magnetic sensor 360 degrees to capture magnetic data; if the spin failed to produce a circle contained in an x-y plane fit a sphere to the captured data; determining offsets based on the center of the sphere; and removing the offsets that are in the z-direction. Computing a magnetic heading reliability of a magnetic sensor by determining an orientation of the sensor at one location; transforming the orientation between two reference frames; measuring a first vector associated with the magnetic field of Earth at the location; processing the first vector to generate a virtual vector when a second location is detected; measuring a second vector associated with the magnetic field of Earth at the second location; and calculating the magnetic heading reliability at the second location based on a comparison of the virtual vector and the second vector.
7 Citations
17 Claims
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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:
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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; sorting the compass data into bins based on compass angles associated with the compass data; determining, for each bin, a weighted best fit line based on a compass reliability; and determining an average slope of the weighted best fit lines of the gyro data subtracted from the compass data in each bin; 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A computer implemented method, the method comprises:
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calculating a tracking path for a person mounted portable device having a magnetic sensor for a compass and a gyro sensor; obtaining tracking data for the portable device along a tracking path comprising a plurality of tracking points, the tracking data including gyro data and compass data associated with the portable device; transforming the gyro data and the compass data into a navigation frame to compensate for tilt of the portable device; computing a compass heading from the compass data, and a gyro heading from the gyro data in the navigation frame; determining a first drift based on a best fit line of the difference between the compass heading and the gyro heading in the navigation frame; estimating compass calibration error by determining a second drift comprising; sorting the compass data into bins based on corresponding compass angles; determining, for each bin, a weighted best fit line based on a compass reliability; determining an average slope of the weighted best fit lines of the gyro data subtracted from compass data in each bin; estimating gyro calibration error by calculating a gyro heading drift based on the first drift and the second drift; updating the gyro data and the compass data based on the estimated gyro calibration error; and correcting at least a portion of the tracking path using the updated gyro data and compass data. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification