A novel marine star tracker/IMU integrated navigation method

Inertial navigation system (INS)/celestial navigation system (CNS) integrated navigation is the efficient means of marine navigation. The horizon reference accuracy is the most important factor for star tracker positioning, however, few methods of celestial horizon references for marine navigation are accurate enough, which immediately reduce the navigation performance. A marine strapdown INS/CNS/Gyrocompass which consists of star tracker and inertial measurement unit (IMU) is presented in this paper. In our proposed method, a new strapdown gyrocompass algorithm in inertial space is proposed, it could observe the pure gravity slow drift in the inertial to give the navigation frame rotation, then provide high precision tilts for star tracker positioning without oscillation error, which is much better than the attitudes provided by strapdown INS algorithm. The gyrocompass algorithm is conducted in IMU as well as strapdown INS algorithm simultaneously, then system errors are estimated with the measurement of position differences based on Kalman filter. Simulation results show that the proposed novel method could make full use of IMU and star tracker information to achieve higher navigation accuracy for the long-endurance vessel sailing.