Hybrid velocity derived heading reference system

Claim 1

A vehicle navigation system including a true heading reference system for determining and controlling the position and velocity of a moveable vehicle, comprising: a receiver/processor on said vehicle for receiving range and range rate signals from a plurality of orbiting navigational satellites and processing said signals together with the stored ephemeris information of said satellites to provide a signal representative of the vehicle's velocity with respect to the earth along the local meridian V n , and its velocity along the local parallel of latitude, V e , said system further comprising sensing apparatus on said vehicle for measuring and providing signals representing the vehicle's axial velocities, V x , V y and V z along the roll, pitch and yaw axes thereof, a vertical gyro adapted to provide instantaneous pitch and roll signals for said vehicle, a converter unit to which said axial velocity signals and said pitch and roll signals are fed to obtain signals representing the along-track velocity, V h , and the cross-track velocity, V d , of said vehicle, a velocity signal processor to which the four said velocity signals V h , V d , V n , and V e are fed, said velocity signal processor providing an output signal representative of the true heading of said vehicle from the vector relationship of said four velocity signals, and apparatus connected to said velocity signal processor for utilizing said output signal for the navigation of said vehicle.