Methods and apparatus for automatic magnetic compensation
First Claim
1. A method for characterizing distortions in the earth'"'"'s magnetic field caused by a vehicle, a magnetometer affixed to the vehicle, said method comprising:
- repeatedly measuring the distorted magnetic field utilizing the magnetometer;
obtaining a three-dimensional orientation of the vehicle axes with respect to the earth at a time of each magnetometer measurement;
receiving undistorted earth magnetic field data for the vicinity of the vehicle relative to the earth at the time of each magnetometer measurement; and
utilizing the magnetic field measurements, the orientations of the vehicle, and the undistorted earth magnetic field data to characterize distortions caused by one or more of the vehicle and magnetometer errors.
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Accused Products
Abstract
A method for characterizing distortions in the earth'"'"'s magnetic field caused by a vehicle having a magnetometer affixed therein is described. The method includes repeatedly measuring the distorted magnetic field utilizing the magnetometer and obtaining a three-dimensional orientation of the vehicle axes with respect to the earth at a time of each magnetometer measurement. The method also includes receiving undistorted earth magnetic field data for the vicinity of the vehicle relative to the earth at the time of each magnetometer measurement and characterizing distortions caused by one or more of the vehicle and magnetometer errors utilizing the magnetic field measurements, the orientations of the vehicle, and the undistorted earth magnetic field data.
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Citations
59 Claims
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1. A method for characterizing distortions in the earth'"'"'s magnetic field caused by a vehicle, a magnetometer affixed to the vehicle, said method comprising:
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repeatedly measuring the distorted magnetic field utilizing the magnetometer;
obtaining a three-dimensional orientation of the vehicle axes with respect to the earth at a time of each magnetometer measurement;
receiving undistorted earth magnetic field data for the vicinity of the vehicle relative to the earth at the time of each magnetometer measurement; and
utilizing the magnetic field measurements, the orientations of the vehicle, and the undistorted earth magnetic field data to characterize distortions caused by one or more of the vehicle and magnetometer errors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of compensating a magnetometer affixed to a vehicle to obtain accurate magnetic heading information for a vehicle orientation, said method comprising
using the magnetometer to measure a distorted earth magnetic field relative to axes of the vehicle; -
determining a pitch and roll orientation of the vehicle axes with respect to the earth;
calculating the distortion of the earth'"'"'s magnetic field for any relative angle between the vehicle axes and the earth'"'"'s undistorted magnetic field; and
determining a magnetic heading based on the magnetometer measurement, adjusted by the pitch and roll orientation of the vehicle, and compensated for distortions of the earth'"'"'s magnetic field. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A method for determining a true earth magnetic field from a magnetic field measured by a magnetometer, said method comprising:
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generating a truth reference field vector, {tilde over (h)}i, from sources of pitch, roll, heading, and position independent of the magnetometer and a three dimensional map of the earth'"'"'s magnetic field;
determining a difference between a vector as measured by the magnetometer and the truth reference vector; and
utilizing the difference to estimate corrections to magnetometer model coefficients. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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- 36. A magnetic compass compensation unit for characterizing distortions in the earth'"'"'s magnetic field caused by a vehicle, in which said unit is mounted, relative to an undisturbed magnetic field of the earth, said unit comprising a processor configured to receive measurements of the distorted magnetic field from a magnetometer, receive an orientation of the vehicle axes with respect to the earth at a time corresponding to each magnetometer measurement, receive undistorted earth magnetic field data for the vicinity of the vehicle relative to the earth at the time corresponding to each magnetometer measurement, and characterize the distortions utilizing the magnetic field measurements, the orientations of the vehicle, and the undistorted earth magnetic field data.
- 48. A processor programmed to generate a truth reference field vector, {tilde over (h)}i, from inertial data and a three dimensional map of the earth'"'"'s magnetic field, determine a difference between a vector as measured by the magnetometer and the truth reference vector, and utilize the difference to estimate corrections to magnetometer model coefficients.
Specification