Vitural Reference Station (VRS) Technique and Its Accuracy Evaluation

Abstract: Along with the extensive applications in multi-disciplinary domain such as Geodetic Survey, Engineering Survey, Aerophotogrammetry, Crustal Movement Monitoring, Construction Engineering Deformation Monitoring, Resources Reconnaissance and Geodynamics, etc. The GPS positioning method is undertaking enormous revolution in order to improve the positioning accuracy and operation efficiency.Virtual Reference Station (VRS) technique, which integrates computer-network management technology, internet technology, wireless communication technology and GPS technology, combines the most advanced multi-reference stations network RTK algorithms and represents the research direction of the new generation of positioning technology following the Conventional RTK technology. The fundamental principle of VRS is to establish the multi-reference stations on the ground and to utilize each observation information comprehensively, and then to correct the errors which are correlated with distance by the precise error model, to produce a virtual reference station colse to the user which does not exist in fact. According to user station and Vitural Reference Station we can form the differences of short base-line or ultra short base-line. So the user can use the differential information received for positioning. Comparing with the conventional RTK, VRS technology has not only improved the precision of positioning and navigation but also expanded the effective coverage of GPS service.On the basis of the introduction to the development of GPS technology, this paper depicts the composition and principle of VRS system in detail, including its composition, principle, workflow, key technology and advantage; Secondly the system's main error sources according to the influence value have been discussed, and the corresponding methods to weaken them have been summarized. In the correction of antenna phase center deviation, methods are put forward to reduce the impact of Choke Ring Antenna phase center deviation on carrier phase observations linear combination; Thirdly combining with the network GPS-Venus system, the paper proposed the model which producing the atmospheric corrections and the orbit corrections of reference station.Finally, this paper takes the Chengdu Network GPS Satellite Positioning Service System (CDVRS) as an experiment platform, with Venus adopted as the processing software in the system control centre, and takes advantage of four practices for the precision of differential positioning to evaluate its differential positioning precision, and to analyze its continuously dynamic observing potency as well as its performance of initialization of the mobile equipment. The results have achieved the expected purpose.Results of experiments: In effective coverage of CDVRS network, RTK positioning accuracy of test points is uniformly distributed; average plane accuracy is 2.24 cm; elevation accuracy is 3.97 cm; the average initialization time is 34 seconds; the track of dynamic RTK is continuously and consistently distributed…
Key words: Virtual Reference Station (VRS); Network RTK; Short Baseline; Accuracy; Initialization

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