Determination of ambiguity in GPS reference station network

　　The key of RTK technology lies in data processing technology and data transmission technology. During RTK positioning, the reference station receiver is required to transmit observation data (pseudo range observation value, phase observation value) and known data to the mobile station receiver in real time. The amount of data is relatively large, and generally requires a Baud of 9600, which is not difficult to achieve in radio.

　　With the continuous development of science and technology, RTK technology has evolved from traditional 1+1 or 1+2 to wide area differential system WADGPS. Some cities have established CORS systems, which greatly improves the measurement range of RTK. Of course, there has also been significant progress in data transmission. The development of radio transmission to current GPRS and GSM networks has greatly improved the efficiency and range of data transmission. In terms of instruments, it not only has high accuracy but also is simpler and easier to operate than traditional RTK.

　　The determination of inter station ambiguity in network RTK reference stations belongs to the problem of solving long-distance static baseline ambiguity. Although the resolution of long-distance static baseline ambiguity is relatively mature, it is difficult to complete the resolution of network RTK benchmark station network ambiguity within more than ten minutes, a few minutes, or even one epoch. Many scholars at home and abroad have conducted some research on this and come up with many methods. Gao Xingwei (2002) proposed a single epoch integer ambiguity search method for network RTK reference stations. Its main idea is not to solve the equation system, but to directly use the three conditions of known observation station coordinates, integer ambiguity, and linear relationship between dual frequency integer ambiguity to search. Compared with traditional methods, the main advantages of this method are fast, simple, practical, and because it is a single epoch ambiguity search, it is not affected by cycle jumps and ionospheric mutations. The single epoch integer ambiguity search method mainly consists of three steps: first, error elimination and calculation, mainly eliminating multipath and other errors, and calculating tropospheric delay; The second is the selection of ambiguity candidate values, which, assuming the maximum double difference ionospheric delay, identifies all integer ambiguity candidate values within this range; The third is the determination of ambiguity

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