星载GPS定轨系统由于其全天侯、价格低、不受卫星高度的影响可达到米级、分米级乃至厘 米级的测轨精度等特点已成为低轨道卫星精密定轨最有效的手段。根据国际上星载GPS测轨的进 展，结合国内对低轨道卫星精密定轨的要求，概述了星载GPS系统的组成和定轨原理，给出了星 载GPS测轨的几种主要方法和数学模型，同时根据TOPEX卫星星载GPS实测数据分析了各种定 轨方法的测轨精度以及影响定轨精度的各种因素。
The system of orbit determination for GPS based satellite has some advantages, for examples, all-weather, low cost, no restriction on satellite altitude, and can achieve the high precision about decimeter or even centimeter. It has become of the most effective orbit determination methods. According to the progress of the international research and the precision orbit requirements of our country for the low satellite based on GPS, we discuss the composition the GPS board satellite system and basic principles of orbit determination, and propose some main methods and models of orbit determination. Based on the data received from the TOPEX satellite, we have given the orbit precisions determined by different methods and analyzed various factors which affect the orbit determination precision.