Coarse alignment for marine SINS using gravity in the inertial frame as a reference

Marine strapdown inertial navigation systems (SINS) inevitably experience disturbing motion, even if the carrier ship is moored. The method of ground coarse alignment, which is based on the assumption that SINS is on a stationary carrier with limited vibration, therefore cannot be used to perform the marine SINS coarse alignment. In this paper, a novel method using the gravity in the inertial frame as a reference is investigated for marine SINS alignment. Its algorithmic principle is described in details. The results obtained from both simulation and turntable-test data show that the attitude determined by this novel method can meet the accuracy requirement of coarse alignment and it can be used as input for fine alignment.