中文摘要：

实时GPS定位需要不断地用接收到的广播星历计算卫星位置，而采用直接法计算会占用大量内存，影响计算速度．在阐述Lagrange等距插值算法的基础上，推导出计算GPS卫星坐标的Lagrange等距插值多项式，并通过算例详细说明了利用广播星历和Lagrange等距插值多项式计算GPS卫星坐标的方法和过程，最后对插值的精度进行了分析；发现当插值多项式的阶数达到10次时，误差不超过1mm．

英文摘要：

It is necessary to get satellite coordinates continually according to broadcast ephemeris received in Realtime GPS positioning. Based on the algorithm of equidistant Lagrange interpolation, the interpolation polynomials of GPS coordinates were deduced. Then the method of equidistant Lagrange interpolation with broadcast ephemeris was demonstraed by a practical example. At last, the precision of the interpolation was analyzed. It was discovered that the error will not exceed 1 mm when the orders are ten.