The GPS implementation plan has three phases

　　The first stage is the project demonstration and preliminary design stage. From 1973 to 1979, four test satellites were launched. The ground receiver and ground tracking network are developed.

　　The second stage is the comprehensive development and test stage. From 1979 to 1984, seven more test satellites were launched and receivers for various purposes were developed. The experiment shows that the accuracy of GPS positioning far exceeds the design standard.

　　The third phase is the practical networking phase. On February 4, 1989, the first GPS working satellite was successfully launched, indicating that the GPS system entered the stage of engineering construction. At the end of 1993, the operational GPS network, the (21+3) GPS constellation, was completed, and in the future the defunct satellites will be replaced according to the plan.

　　Global Positioning system has the characteristics of good performance, high precision and wide application. It is the best navigation and positioning system so far. With the continuous improvement of global positioning system, hardware, software, the application of the field is constantly expanding, has been throughout the national economy in various departments, and gradually into People's Daily life. After nearly 10 years of surveying and mapping departments in China, GPS with all-weather, high precision, automation, high efficiency and other remarkable characteristics, won the trust of the majority of surveying and mapping workers, It has been successfully applied to geodesy, engineering survey, aerial photogrammetry, navigation and control of vehicle, crustal movement monitoring, engineering deformation monitoring, resource exploration, geodynamics and other disciplines, thus bringing a profound technological revolution to the field of surveying and mapping.

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