To study the effect of gravity eccentricity on the ranges,the expression of gravity was educed using spherical harmonic function when the earth is considered as an normal ellipsoid or sphere.

• 为了研究地球的重力偏心对射程的影响,用球谐函数展开法推导了地球为正常椭球体和圆球体时的重力表达式,对地球的重力偏心进行了计算分析,求出了偏心值。