Methods and apparatus for low-cost inertial dead-reckoning using context detection
First Claim
1. A method for determining a user bearing, implemented on a portable device programmed to perform the method comprising:
- determining, with a physical sensor of the portable device, a first geometric orientation of the portable device with respect to gravity at a first time;
determining, with a magnetic sensor of the portable device, a first sensed magnetic field of the portable device in response to an external magnetic field at the first time;
determining, with the magnetic sensor of the portable device, a second sensed magnetic field of the portable device in response to the external magnetic field at a second time; and
determining, with the portable device, a first change in bearing of the portable device at the second time in response to the first geometric orientation, the first sensed magnetic field, and the second sensed magnetic field;
wherein determining with the portable device the first change in bearing comprises determining a change in angle about an external vertical axis between a horizontal component of the first sensed magnetic field with respect to an internal horizontal axis and a horizontal component of the second sensed magnetic field with respect to the internal horizontal axis;
wherein the horizontal component of the first sense magnetic field being determined from a first measured horizontal component, a local gravity vector, and a direction cosine matrix; and
wherein the horizontal component of the second sensed magnetic field being determined from a second measured horizontal component, the local gravity vector, and the direction cosine matrix.
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Accused Products
Abstract
A method for determining a user bearing, implemented on a portable device programmed to perform the method includes determining with a physical sensor of the portable device, a first geometric orientation of the portable device with respect to gravity at a first time, determining with a magnetic sensor of the portable device, a first sensed magnetic field of the portable device in response to an external magnetic field at the first time, determining with the magnetic sensor of the portable device, a second sensed magnetic field of the portable device in response to the external magnetic field at the second time, and determining with the portable device a bearing of the portable device at the second time in response to the first geometric orientation, the first sensed magnetic field, and the second sensed magnetic field.
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Citations
19 Claims
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1. A method for determining a user bearing, implemented on a portable device programmed to perform the method comprising:
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determining, with a physical sensor of the portable device, a first geometric orientation of the portable device with respect to gravity at a first time; determining, with a magnetic sensor of the portable device, a first sensed magnetic field of the portable device in response to an external magnetic field at the first time; determining, with the magnetic sensor of the portable device, a second sensed magnetic field of the portable device in response to the external magnetic field at a second time; and determining, with the portable device, a first change in bearing of the portable device at the second time in response to the first geometric orientation, the first sensed magnetic field, and the second sensed magnetic field; wherein determining with the portable device the first change in bearing comprises determining a change in angle about an external vertical axis between a horizontal component of the first sensed magnetic field with respect to an internal horizontal axis and a horizontal component of the second sensed magnetic field with respect to the internal horizontal axis; wherein the horizontal component of the first sense magnetic field being determined from a first measured horizontal component, a local gravity vector, and a direction cosine matrix; and wherein the horizontal component of the second sensed magnetic field being determined from a second measured horizontal component, the local gravity vector, and the direction cosine matrix. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A portable device for determining a user bearing comprising:
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a physical sensor configured to determine a first geometric orientation of the portable device with respect to gravity at a first time; a magnetic sensor configured to determine a first sensed magnetic field of the portable device in response to an external magnetic field at the first time, wherein the magnetic sensor is configured to determine a second sensed magnetic field of the portable device in response to the external magnetic field at the second time, wherein the first time and the second time are different; and a processor coupled to the physical sensor and the magnetic sensor, wherein the processor is programmed to determine a first change in bearing of the portable device at the second time in response to the first geometric orientation, the first sensed magnetic field, and the second sensed magnetic field; wherein the processor is programmed to determine a change in angle about an external vertical axis between a horizontal component of the first sensed magnetic field with respect to an internal horizontal axis and a horizontal component of the second sensed magnetic field with respect to the internal horizontal axis; wherein the processor is programmed to determine the horizontal component of the first sense magnetic field from a first measured horizontal component, a local gravity vector, and a direction cosine matrix; and wherein processor is programmed to determine the horizontal component of the second sensed magnetic field from a second measured horizontal component, the local gravity vector, and the direction cosine matrix. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification