Construction and Research of Virtual Reference Station

Abstract: With the adventure of GPS technology, surmap(surveying and mapping) industry has undergone enormous changes. Especially in high-precision GPS real-time dynamic positioning technology – RTK , the surmap industry has undergone a qualitative leap. Today,RTK has become the one of measurement technologys used most widely. However, its application has brought about the impact of the restrictions by the ionosphere, troposphere and satellite orbit errors and other factors ,these effects cause a systematic error in the original data, this means that the distance between mobile station and the reference stations was limited – the number has to be reduced to ensure that the system can work effectively.In such circumstances Virtual Reference Station (Virtual Reference Station)has been improved gradually, and provided a new opportunity for long-distance measurement. Using the technology, the system error of reference station data is to reduce or eliminate, so that it means the user can not only increase the distance between mobile stations and reference points by users, but also enhance the reliability of the system and reduce the initialization of the equipment Time. The technology is used not only for building new network, but can also improving existing, as-built network performance. Virtual Reference Station (VRS) technology is a kind of multi-reference points carrier phase positioning technology (also known as network RTK technology). The principle is to establish a virtual reference station near the user vicinity station, and in accordance with the actual observation values of the reference stations in networks all around we can calculate the virtual observation values on the Virtual Reference Station. Virtually it is equivalent that this observation station closes to the mobile station (usually a few metres to tens of meters), so after the establishment of the virtual reference station, the dynamic user adopts the conventional RTK technology to operate with virtual reference station for real-time access to relatively more precise positioning of the targeted results. This paper give a detailed summary and research for technology principles of Virtual Reference Station (VRS),and offer an overall clarify for the construction of Virtual Reference Station (VRS) system. The main contents are as follows:1.First, to describe the concept and characteristics of the Virtual Reference Station (VRS) technology in details, overview the development of the Virtual Reference Station (VRS) technology ,and to introduce briefly the current status of domestic and international Virtual Reference Station (VRS) technology applications.2.Because of the principles’similarity of Virtual Reference Station (VRS) technology and GPS, network RTK, this paper also recall the development of GPS and expound more detailedly the basic principles of GPS and the classification of network RTK and GPS. With comparing the Virtual Reference Station (VRS) technology with traditional GPS technology and the networks RTK technology, the superiority of Virtual Reference Station (VRS) is pointed out.3.The composition of Virtual Reference Station (VRS), working principle and the key technology are expounded mainly, and under the basic condition of the solution of observation equation, whole ambiguity and the calculation of the correction, the author try to gradually discuss and calculate the mathematical model of Virtual Reference Station (VRS).4.The error sources and error analysis of the Virtual Reference Station (VRS) are researched extensively and basically. Have discussed the delay in the ionosphere, troposphere delay, the satellite orbit errors, multi-path effect, the clock error and the station attribute characteristics of the equipment itself generated by the error, in Which discussed the ionosphere delay, delay in the troposphere, the satellite orbit errors, multi-path effect of the error in details, focus on the ionospheric delay and tropospheric delay in error, and gives the corresponding mathematical models and the basis of the solution Programme.5.Finally, to combine "Harbin Double Star navigation system," make the construction design for Virtual Reference Station (VRS) system. More comprehensive exposition of Virtual Reference Station (VRS) system-building programme, feasibility analysis, the building process, the core technology and the building of significance and role. And a systemic test and the precision assessment are carried out…
Key words: network RTK; Virtual Reference Station; integer ambiguity; ionosphere; troposphere; delay in error

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