Initial Alignment of Shipborne SINS under Ship Motion

—The paper focuses on improving the accuracy and shortening the time of shipborne SINS initial alignment under the ship yawing, rolling and pitching motions. This is achieved by implementing a two-step SINS alignment algorithm. At the first step, the ship attitude parameters are approximately autonomously estimated by data from gyros and accelerometers. The description of ship dynamics is introduced, and water speed log data are applied. At the second step, the system fine alignment is performed with account for alignment errors after the completion of the first step. Speed and position measurements from external aids are additionally applied during the fine alignment. Kalman filter algorithms are used at the first and second steps. Results from bench and sea tests for SINS on navigation grade FOGs under the ship yawing, rolling and pitching motion are provided.