Effects of time synchronization errors in GNSS-aided INS

The effects of time synchronization errors in a GNSS-aided inertial navigation system (INS) are studied in terms of the increased error covariance of the state vector. Expressions for evaluating the error covariance of the navigation state vector-given the vehicle trajectory and the model of the INS error dynamics-are derived. Two different cases are studied in some detail. The first case considers a navigation system in which the timing error is not included in the integration filter. This leads to a system with an increased error covariance and a bias in the estimated forward acceleration. In the second case, a parameterization of the timing error is included as a part of the estimation problem in the data integration. Simulation results show that by including the timing error in the estimation problem, almost perfect time synchronization is obtained and the bias in the forward acceleration is removed.