Body Frame Constraint for a GNSS/MEMS INS Integrated System in Land Vehicle Navigation

For global navigation satellite system(GNSS) and micro-electro mechanical system (MEMS) inertial navigation system (INS) integrated system in land vehicle application, a particular constraint based on features of a vehicle's motion is setup on its body frame to improve the system performance. Body frame constraint limits the velocities along the plane perpendicular to the vehicle's moving direction to approximate zero, which accordingly introduces couple of additionally virtual measurements into the extended Kalman filter (EKF) that is typically applied for two systems fusion. Thanks to those virtual measurements, the EKF is able to keep its measurement updates even over GNSS signal outage period. The filter continuously produces error estimations and feedbacks during the absence of external observables from GNSS, whatever the vehicle's dynamics is. The field test indicates that the system accuracy of positioning can be improved by 75% over 30 s GNSS outages and the accuracy of attitude and velocity is improved as well.