中文摘要：

在2004年发布的GPS界面接口控制文档中提出一种对GPS 16参数广播星历进行改进的GPS 18参数广播星历.本文介绍了GPS 16参数广播星历的拟合算法,对两类GPS广播星历参数进行比较,分析了改进参数的变化规律及特性.计算结果表明,GPS 16参数广播星历的改进参数具有明显的约12 h和13.5 d的周期变化特性,新提出的GPS 18参数广播星历能够更好地逼近GPS卫星真实轨道.

英文摘要：

A new 18-parameter GPS broadcast ephemeris improved on the basis of 16-parameter GPS broadcast ephemeris is introduced in the GPS interface control document issued in 2004.But the improved reasons have not been analyzed.In this paper,the fitting algorithm of 16-parameter GPS broadcast ephemeris is briefly introduced,the differences of the two kinds of GPS broadcast ephemeris parameters are compared,and the change regularity and properties of the improved parameters are analyzed.Calculation results show that the improved parameters of 16-parameter GPS broadcast ephemeris have obvious periodic variation characteristics with a period of about 12 hours and 13.5days,and the newly proposed 18-parameter GPS broadcast ephemeris can better approach the real orbit of GPS satellites.