美国第一代导航卫星“子午仪”的广泛应用已充分显示出人造地球卫星用于导航的优越性。但是,“子午仪”只能提供断续的二维导航信息,大大限制了动态用户的应用。目前正在研制试验的“导航星全球定位系统”是美国第二代导航卫星,预计八十年代中期可 The widespread use of the first generation navigation satellite “Meridian” in the United States has fully demonstrated the superiority of the artificial Earth satellite for navigation. However, “Meridian ” can only provide intermittent two-dimensional navigation information, greatly limiting the dynamic user’s application. Currently under test, the “Navstar Global Positioning System” is the second-generation navigation satellite in the United States and is expected to be available in the mid-1980s