| GPS (global positioning system) has been widely used in survey, navigation, positioning and other fields due to its high efficiency, global, all-weather, and many other advantages. Along with GPS applied thorough, people put forward with measuring accuracy more higher request for using GPS technology in measuring and positioning, a variety of enhancement techniques that can improve positioning accuracy have emerged, one of the most basic techniques is DGPS. It can weaken or even eliminate the public error of measurement to improve the precision of positioning through calculation difference between stations, satellites, or neighbor epochs due to the strong spatial correlation and temporal correlation of GPS measurement. The research of DGPS based on OEM (original equipment manufacturer) board has high practicability, because DGPS device is expensive but OEM board is cheap and flexible.In this paper, the AC-12 GPS-OEM board produced by THALES Co. of France is adopted as the base station receiver, the key problems of DGPS are been researched, the relevant program is compiled and a summary of pseudo-range DGPS system is implemented. The main work in this paper is concluded as follows:1. The principle of single-point positioning and error sources are discussed, the error correction of DGPS is analysed, the principles, models and their respective advantages and disadvantages of position DGPS, pseudo-range DGPS, phase smoothing pseudo-range DGPS and carrier phase DGPS are compared.2. The original data formats of AC 12 OEM board and the GPS data processing general format RINEX are studied, and the program applied to conversion of OEM raw data to RINEX format is realized.3. The methods of calculate satellite position and clock offset by using broadcast ephemeris or precise ephemeredes.4. The corresponding program is compiled on the platform MATLAB7.0 to realize the sub-meter pseudo-range DGPS, and a lot of experiments are done to prove the effectiveness of the program.
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