The GPS project will be implemented in three phases:

　　The first stage is the project demonstration and preliminary design stage.

　　From 1978 to 1979, four test satellites were launched from Vandenberg Air Force Base in California using Gemini rockets. The satellites operated in an orbit with a major axis of 26,560 km and an inclination of 64 degrees. The orbital altitude is 20,00km. In this stage, the ground receiver and ground tracking network are mainly developed, and the results are satisfactory.

　　The second stage is the comprehensive development and test stage.

　　From 1979 to 1984, seven more test satellites, called BLOCK I, were launched to develop receivers for various purposes. The experiments show that the GPS positioning accuracy far exceeds the design standard, using coarse code positioning, its accuracy can reach 14 meters.

　　The third phase is the practical networking phase.

　　The first GPS working satellite was launched on February 4, 1989. The satellites in this phase were called BLOCK II and BLOCK IIA. At this stage, the GPS system is declared to enter the state of engineering construction. The GPS network used at the end of 1993, the (21+3) GPS constellation, has been completed and the defunct satellites will be replaced in the future according to the plan.

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