A fast inertial frame alignment algorithm based on horizontal alignment information for marine SINS

In this paper, a improved inertial frame alignment algorithm is proposed, which significantly improves the accuracy and time cost of the traditional inertial frame coarse alignment algorithm. Firstly, a dimensionality reduction Gauss-Hermite filter algorithm is employed in the horizontal fine alignment phase. Secondly, according to the feature of the gravity, that the horizontal components of the gravity projected in horizontal reference frame is zero, the projection of the gravity in body inertial coordinate frame could be calculated easily after the horizontal fine alignment. Thirdly, a weighted smoothing algorithm is used to adjust the gravity which obtained after the horizontal fine alignment phase, and then the initial alignment algorithm is accomplished. The simulation results show that the alignment time can be greatly reduced. And the fast initial alignment algorithm can achieve the medium accuracy within 6 minutes. That meets the accuracy requirement of the medium accuracy marine SINS.