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.
19 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