M. Saidani, P. Sarri, A. Guinamard, D. Gallego Maya, SBG Systems, France

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RTK (Real Time Kinematic) [1] is a positioning approach that provides centimeter level accuracy by using a reference station. When the rover and the base station are in proximity (short baseline), all common mode errors are eliminated by the double difference, allowing carrier phase ambiguity resolution [2]. In the medium and long baseline cases, the ionospheric and tropospheric delays are not completely eliminated by the double difference which make them critical factors for the positioning accuracy. Thus, the availability of base station limited the application of RTK, especially in certain regions where the closest base station can only be found over 50 km. Algorithms like RTK long baseline [3] and VBS (virtual base station) [4] emerged as an alternative. The virtual base station (VBS) algorithm processes the surrounding bases to generate a virtual one within a short distance of the moving rover. By doing so, the atmospheric errors will continue to be eliminated in the double-difference model and the RTK processing will be presumably assured all over the mainland continents. A performance assessment of the algorithm is conducted under various conditions, including high ionospheric activity, high baseline, harsh multipath environments and finally in a long trajectory. The results show that the developed VBS algorithm ensures centimeter-level accuracy even under the hardest conditions.