The Study On The Experiment System Of GPS Principle

Taking the GPS (Global Positioning System) as representative, the satellite navigation application has become one of the eight biggest industries. It is being developed rapidly in civil, but our country is one of the biggest application countries rather than greatest power countries, because the core technology and relative services lagging behind the developed countries. Base on the insight on the principles of GPS and the problems in the processing of teaching, the Experiment System of GPS Principle was designed and developed. It is composed of Base Station and Rover Station to display principle of GPS positioning, differential positioning and fusion application of GSM, GPRS and GPS. For hardware design, the system chooses the types of modules for the components in the light of technology integration and the interface circuit was developed. The software is developed on the platform of VC++ 6.0 with friendly interface. It is composed of Base Station, Rover Station and Experiment. Rover Station is made up of coordinate module and positioning module. The coordinate module is to show the difference, relation and conversion between coordinates, and positioning module to show GPS positioning principle and the differential positioning principle together with Base Station, besides it works as monitor terminal during communication experiments, receive the GGA sentences from client terminal. The Base Station is to display the formation process of pesudorange deviation, transmits the RTCM sentences on real-time to Rover Station, and works as client terminal during communication experiments. Experiment software adopts DLL technology to provide parameters such as pesudorange, satellites' velocity, etc, and the interface to experimenter with which experimenter can program by themselves. In the test, positioning data were collected from OEM module working in GPS mode and DGPS module, statistics shows that accuracy of the OEM module works in DGPS imporves significantlty, the position data computed by software with the original parameters from OEM module also collected. Comparative test shows that both Base Station and Rover Station can works smoothly. In communication test, it realize the communication between the monitor terminal and client terminal by GSM and GPRS, experiments show that GSM corresponds has certainly time to delay and GPRS is better than GSM on the speed of transmission and the responding time. The results of test show that hardware runs stably and software works smoothly, and that system achieves the aims of design and meets the need of teaching.