Abstract: ObjectiveIn complex Marine environment, the vertical movement of ships often has a significant impact on the safety of offshore engineering operations. Active heave compensation devices can compensation for the vertical movement of ships, and all of its compensation commands need to be based on the vertical vessel attitude motion (roll, pitch,heave) as an input. Therefore, a ship attitude estimation method based on low-cost inertial measurement unit is proposed. MethodsBased on the mathematical model between quaternion and ship rotating motion, the linear acceleration of the ship when it is in the dynamic state is taken into account, and a virtual yaw measurement value is introduced, an ship attitude observer is designed. The extended Kalman filter algorithm is used to estimate the ship attitude. ResultsBy simulation analysis and six-DOF platform experiments, and the estimation errors of the ship's roll angle and pitch angle are within 5%, which are comparable to the estimation errors of commonly used motion reference units. In addition, the method can also estimate the relative change of yaw angle with an estimation error of no more than 8%.ConclusionsThe analysis experiments under different sea conditions verified the accuracy and effectiveness of the ship attitude estimation method, it can provide high-precision ship attitude data for wave compensation equipment, enhancing the safety and efficiency of Marine engineering operations.