Abstract: The traditional strapdown inertial navigation algorithm is to calculate the ground velocity based on integral of specific force transformation, which is solved using first-order approximation and second-order truncation. The influence of approximate integration errors on navigation precision cannot be ignored. In order to eliminate this influence, an improved strapdown inertial navigation algorithm with high precision is presented by using split integration scheme in the inertial reference frame. An analytical solution of the integrated transformed specific force increment is obtained for the thrust velocity defined by integral of specific force in the inertial frame, and a compensation scheme based on modified velocity increment is proposed for sculling error by analyzing its cause, an exact solution of the thrust velocity which can completely offset the dynamic errors, including coning error, rotation error and sculling error, is obtained. Both coning and sculling errors may be computed directly using the traditional optimization algorithms. A complete strapdown inertial navigation algorithm with high precision is developed by extending the thrust velocity update ideas into integration of the gravitational acceleration and position update. The significant advantages of the algorithm in the overall performance are demonstrated by the simulation test results under complex dynamic environment.

Key words: control and navigation technology of aerocraft, absolute velocity, thrust velocity, modified velocity increment, integrated transformed specific force increment, gravitational velocity