Patent US 4,254,465

Estimators of a vehicle's position and attitude with respect to the earth are generated continuously by integrating the outputs of translational and rotational accelerometers that are attached to the vehicle. These estimators are corrected by comparing them to corresponding reference dynamic variables measured independently by instruments onboard the vehicle. The estimators are modified by slowly responding servo loops to equal their corresponding reference variables. Differences between certain of the estimators and their corresponding reference dynamic variables are used in generating feedback signals for correcting other of the estimators. By combining various of the estimators, system outputs representing sideslip angle and change in cross-track velocity can be generated.