Patent ID: 9052203
Filing Date: 2015-06-09
Classification: G01C

Abstract:
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.