Using Virtual Reference Stations “VRS” in Positioning

Abstract

The first chapter of this thesis is representing the motivation behind the development of the CORS networks and the virtual station technique that is now a world widely used technique and the preferred technique by the most of surveyors and surveying departments in the world, chapter one shows how this technique saves power, money and as well it saves time and double cost of purchasing the same equipment twice and explains the difference between this technique and the classical methods of survey using single base station. Chapter two is showing the idea and advantages of the VRS concept asit uses a network RTK processing algorithms andthere isno interact of the receiver in the algorithmand no software is required, so it is totally independent solution coming from the VRS network control center. The communication link is established between the rover and the control center using GSM and data links. Furthermore in chapter two a brief on modelling the ionospheric and tropospheric errors in the VRS network and the receiver itself in order to get the optimal performance and the highest accuracy possible. Chapter three is showing the Egyptian VRS network that is being used now as a CORS network because of some restrictions on using the communications links between the rover and the control center, it shows the design and location selection of the Egyptian network stations, also it shows the installation done and instruments used to create the Egyptian VRS network, a transformation parameters was obtained to solve the problem of using more than one coordinate system in Egypt. A test was done to investigate the accuracy of the Egyptian CORS network in chapter four showing the needed time to get mm accuracy using the Egyptian CORS network solution in post processing mode. It was mandatory to use a real VRS network operating in RTK mode and that is done in chapter five using the Dubai VRS network that operates already in real time mode, some tests were done to investigate the accuracy of the network, coverage, absolute and relative accuracy and the difference between using single base station versus using network solution.