CALIBRATION TECHNIQUES FOR AN ELECTRONIC COMPASS IN A PORTABLE DEVICE
First Claim
1. A portable device comprising:
- a three axis magnetic sensor;
a first compass calibrator to compute a first offset field based on a set of magnetic field measurements by the sensor that define a generally spherical surface, and to use the first offset field to compute a first geomagnetic direction;
a second compass calibrator to compute a second offset field based on a set of magnetic field measurements by the sensor that define a generally circular path, and to use the second offset field to compute a second geomagnetic direction; and
a compass direction output module that selects one of the first and second geomagnetic fields to be its direction output, depending upon how the portable device is being carried by its user.
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Accused Products
Abstract
Measurement data is collected from a magnetic sensor in a portable device, while the device is being carried by its end user and without requiring the end user to deliberately rotate or position the device while the output data is being collected. For example, the device may be held in the user'"'"'s hand while walking or standing, or it may be fixed to the dashboard of an automobile or boat. Measurement data may also be collected from one or more positing, orientation or movement sensors. The collected measurement data from one or both of the magnetic sensor and the position, orientation or movement sensor is processed. In response, either a 2D compass calibration process or a 3D process is signaled to be performed. Other embodiments are also described and claimed.
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Citations
14 Claims
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1. A portable device comprising:
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a three axis magnetic sensor; a first compass calibrator to compute a first offset field based on a set of magnetic field measurements by the sensor that define a generally spherical surface, and to use the first offset field to compute a first geomagnetic direction; a second compass calibrator to compute a second offset field based on a set of magnetic field measurements by the sensor that define a generally circular path, and to use the second offset field to compute a second geomagnetic direction; and a compass direction output module that selects one of the first and second geomagnetic fields to be its direction output, depending upon how the portable device is being carried by its user. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An article of manufacture, comprising:
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data storage having stored therein data that programs a processor to perform a calibration routine on an electronic compass that has a 3-axis magnetic sensor, to compute an offset field for the compass, wherein the calibration routine is to determine that the magnetic sensor has remained essentially level, in that it has not rotated about the horizontal plane, for at least a predetermined time interval while moving along the horizontal plane, and in response select a 2D calibration process to be performed on the sensor for computing the interference field, and wherein the calibration routine is to determine that the sensor is sufficiently tilting or rotating about the horizontal plane and in response select a 3D calibration process to be performed on the sensor for computing the interference field. - View Dependent Claims (8, 9)
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10. A machine-implemented method for operating a portable device having a magnetic sensor to provide a compass function, the method comprising:
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collecting measurement data from the magnetic sensor in the portable device, while the device is being carried by its end user and without requiring the end user to deliberately rotate or position the device while the output data is being collected; collecting measurement data from one or more position, orientation or movement (POM) sensors in the portable device, while the device is being carried by its end user and without requiring the end user to deliberately rotate or position thee device while the output data is being collected; and processing collected measurement data from one or both of the magnetic sensor and the POM sensor and in response signaling that one of a 2D compass calibration process and a 3D compass calibration process be performed upon the magnetic sensor. - View Dependent Claims (11, 12, 13, 14)
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Specification