Loose coupling of inertial and satellite navigation measurements with the aid of extended Kalman filter with attitude quaternion

It is noted that the observation vector of the proposed coupling filter contains only antenna coordinates, measured by GNSS receiver. The errors of the attitude quaternion are considered as a small rotation vector which is used to construct an a-posteriori attitude error quaternion. The error quaternion is used for multiplicative correction of an a-priori estimate of an attitude quaternion obtained by solving inertial navigation equations. A-priori estimates of the remaining components of the filter’s state vector are corrected in an additive way. An experimental testing results of the coupling filter are provided. A numerical observability analysis of the filter’s state vector on experimental trajectories has been performed.