Patent ID: 7346452

Claim:
A method of determining the alignment of an inertial measurement unit of an inertial/GPS receiver that is in motion at start-up, the method including: A. receiving signals from a plurality of GPS satellites; B. acquiring and tracking carriers and codes in the satellite signals; C. determining a GPS position and an associated GPS velocity vector; D. identifying a location on a surface model that corresponds to the GPS position and determining the relative orientation of a corresponding surface plane; E. using the orientation of the surface plane and the GPS velocity vector to determine pitch, roll and heading of a vehicle on which the receiver is mounted; F. using the pitch, roll and heading information and information about an angular relationship between the vehicle and a body frame associated with the inertial measurement unit to determine an angular relationship between the inertial measurement unit body frame and a reference frame; G. using GPS measurements and inertial measurements to determine one or more of the position, velocity and attitude of the vehicle; and H. displaying one or more of the position, velocity and attitude of the vehicle.