Patent ID: 8019542

Claim:
A method of stabilizing heading in an inertial navigation system, the method comprising: operating an inertial measurement unit comprising horizontal-sensing elements and off-horizontal-sensing elements, while the inertial measurement unit is in a first orientation, wherein the horizontal-sensing elements are oriented in a horizontal reference plane; calibrating the horizontal-sensing elements of the inertial measurement unit based on horizontal aiding measurements; forward-rotating the inertial measurement unit by a selected-rotation angle about a horizontal-rotation axis, wherein the inertial measurement unit is oriented in a second orientation, and wherein, while the inertial measurement unit is in the second orientation, the off-horizontal-sensing elements are oriented in the horizontal reference plane; operating the forward-rotated inertial measurement unit while the inertial measurement unit is in the second orientation; and calibrating the rotated off-horizontal-sensing elements based on horizontal aiding measurements while the inertial measurement unit is in the second orientation.