Patent ID: 8521428

Claim:
A computer-implemented method for estimating heading of a vehicle, comprising: receiving first angular rate measurements from a plurality of rate sensors mounted on a rotatable assembly at a first time, the rotatable assembly rotated to a first rotation angle and the vehicle having first heading at the first time; receiving second angular rate measurements from the plurality of rate sensors at a second time subsequent to the first time, the rotatable assembly rotated to a second rotation angle, the vehicle having second heading that is substantially the same as the first heading at the second time; computing the first heading relative to a reference vector representing rotation of the Earth based on the first angular rate measurements and the second angular rate measurements; and computing a third heading of the vehicle at a third time subsequent to the second time based on the first heading responsive to receiving third angular rate measurements from the plurality of rate sensors; wherein computing the first heading comprises: projecting the first and second rate measurements to a tangent plane of the Earth to obtain tangent plane data; fitting the tangent plane data to a conic; constraining the conic to a circle to obtain a circle transform; projecting the tangent plane data through the circle transform to obtain transformed data; fitting the transformed data to a polynomial in the tangent plane; computing tangent plane angles of the vehicle with respect to a reference direction; and detecting zero-crossing of the tangent plane angles by interpolating a rotation angle of the rotatable assembly to obtain the first heading.