A Virtual Reference Station Algorithm Development for a Network RTK System

Concepts of multiple reference stations—Virtual Reference Station (VRS) for instance—have been developed during the last two decades to overcome the traditional RTK deficiencies. The basic idea behind the VRS method is the application of spatiotemporal dependence of errors to reduce the effects of biases on virtually generated observations. This amelioration improves the final coordinates and reduces the number of permanent stations settlement over a regional network. The virtual station must be as close as possible to the rover station. For this purpose, the rovers have to transmit their approximate coordinates to a data process center (the master reference station), which can be obtained using the navigation solution. The approximate coordinates of the rover are then selected as the position of the virtual station. Therefore the virtual observations can be generated at the VRS position and corrections due to the dispersive and nondispersive biases are implemented to the observations. This generation of virtual observations improves the final coordinates and reduces the number of permanent stations settlement over a regional network. In this article the VRS generation algorithm is developed and applied to six GPS stations of NGS (National Geodetic Survey) permanent network. Various error interpolation methods are tested for the VRS algorithm efficiency. The results prove that the VRS algorithm works correctly, which can be used for regional and national networks. The results were shown not much to be dependent on the choice of the interpolation method. However, the error mitigation algorithm plays the most important role.