Fine Alignment Algorithm of Strapdown Inertial Navigation System in Moorage Based on Ship's Instantaneous Velocity

In order to improve the precision of inertial navigation system(SINS)alignment in moorage,a fine alignment algorithm using ship's instantaneous velocity as the reference velocity is proposed.Through a lot of experiments,signals of the SINS velocity are analyzed.Then a high-pass digital filter is designed to separate the ship's instantaneous velocity from the SINS's output after coarse alignment.The SINS error model for the mooring situation is established.Finally,the ship's instantaneous velocity is used as the reference velocity to accomplish the fine alignment by Kalman filter.Experiment results indicate that the error of calculated instantaneous velocity is less than 0.08m/s,and the novel alignment method has advantages on accuracy and repeatability.