Trajectory correction projectile is a hotspot of information-based ammunition at present. To compare factual trajectory with theory trajectory of the projectile fired by ship borne gun, and to create correction instruction, the model is set up that is used to convert the relative trajectory coordinates measured by ship borne tracking radar into the absolute coordinate system that is immobile on the earth, and solve problems of measuring trajectory, because of warship navigating, sway and fluctuation. The model is proved by simulating to be practicable and reference to make further research on trajectory identification algorithms.