Researches on Virtual Reference Station (VRS) and Differential Correction Data

Abstract: GPS carrier phase surveying technique has been developed from static, fast static to real time kinematic(RTK) positioning , which changed the acquiring way of spatial information and enlarged the area of GPS application .But RTK technique is affected by atmosphere errors, multipath effects errors etc. The distance between rover station and reference is limited to less than 20 km .The distance-dependant errors may cause the resolution of integer ambiguity more difficult, and the time-cost. More seriously it can degrade the results.With the construction of many kinds of CORS, the network RTK consisting of multi-base stations appears and ravels out the limitations of traditional RTK technique. The typical network RTK technique is Virtual Reference Station (VRS). VRS is a kind of GPS real-time kinematic positioning technique based on multi-base stations. The principle of VRS is: building a Virtual Reference Station on a predefined position (near the rover station) inside the multi-base stations network, real-timely obtaining the systematic errors of predefined position and generating a series of virtual observables (VRS observables or differential correction data). Due to the short distance between rover station and VRS, the regional RTK positioning can be realized more accurately and reliably, by using VRS observables. VRS technique is a kind of positioning method integrating the Internet, wireless communication technique, computer network, database and GPS, and represents a novel developing trend after the traditional RTK technique.Firstly, the thesis compares the traditional RTK technique with network RTK technique, summaries the network RTK technique and introduces the development, classifications and merits of network RTK technique. Secondly, the theories of VRS, including conception, principles, functioning method, key technique, merits and shortcomings, are introduced in details. And then th…
Key words: Global Positioning System (GPS); Real Time Kinematic (RTK); Virtual Reference Station (VRS); Differential Correction Data; RTCM (Radio Technical Commission For Maritime Service) Recommended Standards; Troposphere; Ionosphere; Modeling

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