Abstract: In track simulation,the corresponding earth equivalent radius of a track in a specific range is approximate to the earth curvature radius of the latitudinal location of the target.With track at different latitude,the corresponding earth curvature radius may be different.Through analysis of the influence of latitudinal earth curvature radius on a track,the latitudinal earth curvature radius can be proved to be approximate to the earth equivalent radius.This method reduces the complexity calculation.

Key words: track simulation；earth curvature radius, Error analysis