中文摘要：

空间信号（SIS）精度是卫星导航系统的基本性能之一,而卫星的用户测距误差（URE）是SIS精度的重要指标。基于轨道误差及钟差误差研究了GPS（全球定位系统）和BDS（北斗卫星导航系统）的SIS URE评估方法,并利用实测数据评估了GPS和BDS的SIS性能。验证结果表明：GPS的SIS URE均优于2.2 m,BDS SIS URE除GEO-01和GEO-04卫星外均优于2.5 m,符合GPS标准定位服务性能规范（2008年）及北斗卫星导航系统公开服务性能规范（1.0版）对SIS URE的指标要求。

英文摘要：

Signal-in-space（SIS） accuracy is one of the basic performance of satellite navigation system, and the user range error（URE） of satellite is often used as the important indicator of SIS accuracy. Based on the orbit error and clock error, the SIS URE evaluation methods of GPS and BDS were discussed. And the SIS performance of GPS and BDS were evaluated by using the measured data. The results show that all the SIS URE of GPS satellites are better than 2.2 m. In addition, except GEO-01 and GEO-04, the SIS URE of other Bei Dou satellites are better than 2.5 m.And it conforms the indicators of GPS standard positioning service performance standard（GPS SPS PS, 2008） and BDS open service performance standard（BDS OS PS, 1.0）.