Real Time Kinematics using Differential Carrier Phase Measurements

Abstract

In car, train or air navigation, in precision farming, in geodesy or in survey, the level of required navigation performance differs. Under performance, it is often meant accuracy. GPS and Differential GPS provide accuracies of up to 100m and 5m respectively, also depends on the type of receiver (single frequency or dual frequency). Recently the focus has shifted to RTK Applications (Real Time Kinematics), where the required accuracy is much greater. By using the carrier phase measurements, mm level accuracy can be obtained. The aim of this thesis is to study carrier phase measurements, the various existing ambiguity resolution algorithms and implement one of the algorithms to fix the ambiguities and thus determine the user position with high precision. In this case the LAMBDA method is used to fix the ambiguities, which is one of the most popular and fastest methods followed for ambiguity estimation. This master thesis describes how the LAMBDA algorithm and the differential carrier phase measurements have been implemented. The entire application is written in C/C++ and uses the MATLAB runtime engine to plot graphs. The application uses post processed files of the International GNSS Service (IGS) (RINEX Observation and Navigation files) as reference files to calculate the position estimates. The application stores all intermediate and final results in output files. Results have been simulated on one day and weekly basis, where the position estimates are calculated with all the readings in the observation files. They also help us to find the offsets associated with particular stations, due to either Ionospheric or tropospheric activities present in that region. One has to keep in mind that this application has been developed for post processing purposes and cannot be used for real time scenarios.