Two different coarse alignment algorithms for Fiber Optic Gyro (FOG) Inertial Navigation System (INS) based on inertial research frame are discussed with this paper. the optimal value, and show that in different operational conditions, the coarse positioning algorithms used for FOG INS are different in order to accomplish better performance. Lastly, the experiment results validate the effectiveness of the proposed algorithm. knowledge of initial conditions . Only the measurement info from accelerometers and FOG outputs can be used. This truth causes the development of a non-linear positioning algorithm, and analytic methods are generally utilized for coarse positioning. In the ground foundation, the attitude can be identified directly from the analytic coarse positioning method using the gravity and earth rotation vectors . Normally, the accuracy of this method can meet the requirement of good positioning under the disturbance of limited vibration. However, FOG INS is usually applied in complex and volatile environments, and then the system has to withstand random motions which may be violent, such as a ships pitch and roll . The ground PP1 supplier coarse alignment techniques, henceforth, can not be used, since the measurement of the earth rotation rate provided by FOG is definitely disturbed by high rotational ideals (several orders of magnitude greater than the earth rotation rate) . In order to deal with this problem, a IL1B new analytic coarse positioning method based on the inertial research framework for FOG INS has been provided . This method is definitely developed based PP1 supplier on the fact the gravity indicated in inertial space defines a cone whose main axis is the rotational axis of the PP1 supplier Earth. Many researchers possess investigated this topic, primarily based on the structure of noncollinear vectors [9,12,13]. In Research 9, the noncollinear vectors are constructed by a velocity vector that is determined by gravity vector integration. In Research 12, the authors provided a building method by which the noncollinear vectors are acquired by a position vector that is produced by velocity vector integration (acquired by gravity integration). All of them have a lack of rigorous selection of integration time, so the overall performance of the coarse alignment algorithms may not be ideal. In order to give a criterion for selecting the integration time, and make the selection more accurate, the optimal parameter design of PP1 supplier coarse positioning algorithms for FOG INS is done with this paper. First, the analysis of these two algorithms is made, and it is focused on the quasi-stationary conditions. Then with the analysis of the error characteristics, the optimal parameter design of these two algorithms is derived. Finally, based on the analysis and ideal parameter design, the adequate selection of probably the most accurate algorithm for FOG INS according to the actual operational conditions is definitely provided. The remainder of this paper is definitely organized as follows: the coordinate frames used in this paper are tackled in Section 2. In Section 3, the basic principle of the new analytic coarse positioning method for FOG INS is definitely introduced. Then the algorithms produced by the two different constructions are offered in Section 4. In Section 5, the processes of the error analysis and optimal parameter design are performed. Finally, in Section 6 and Section 7, simulation and experiment results verify the analysis made in Section 5, and Section 8 concludes this paper. 2. Coordinate Framework Definitions The coordinate frames used in this paper are defined as follows: (1) The framework is the body coordinate framework. The axis is definitely parallel to the vehicle’s lateral axis and points to the right. The axis is definitely parallel to the vehicle’s longitudinal.