The first stage is the scheme argumentation and preliminary design stage.

　　From 1978 to 1979, four test satellites were launched using Gemini rockets from Vandenburg Air Force Base in California, with a long half axis of 26560km and an inclination of 64 degrees. The track height is 20000km. In this stage, we mainly developed a ground receiver and established a ground tracking network, with satisfactory results.

　　The second stage is the comprehensive development and testing stage.

　　From 1979 to 1984, seven experimental satellites called "BLOCK I" were launched and receivers for various purposes were developed. Experiments have shown that GPS positioning accuracy far exceeds design standards, and using coarse code positioning can achieve an accuracy of up to 14 meters.

　　The third stage is the practical networking stage.

　　On February 4, 1989, the first GPS working satellite was successfully launched, and the satellites in this stage were called "BLOCK II" and "BLOCK IIA". This stage declares that the GPS system has entered the state of engineering construction. At the end of 1993, the practical GPS network, known as the (21+3) GPS constellation, had been completed, and in the future, failed satellites will be replaced according to the plan.

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