GPS and Galileo Integer Ambiguity Resolution Enabled PPP (PPP - RTK)
The next generations Global Navigation Satellite Systems (GNSSs) have the potential to enable a wide range of applications for positioning, navigation and timing. The positioning accuracy, reliability and satellite availability will be improved as compared to today’s solutions, provided that a combination of the satellite systems is used. The GNSS receivers collect multi-GNSS code and carrierphase observations with decimetre-level and millimetre-level precision respectively. However, only when the phase ambiguities can be solved to their true integer values is it possible to take full advantage of the precise phase measurements and solve very precise receiver positions. This technique is referred to as real-time kinematic (RTK). When the frequencies overlap between the systems one can further calibrate the so called between-receiver differential inter-system biases (ISBs) as to strengthen the model. A common ‘pivot’ satellite can then be used when parameterizing the doubledifferenced ambiguities. In this PhD thesis by publication multi-GNSS positioning results when combining the American Global Positioning System (GPS), Chinese BeiDou Navigation Satellite System (BDS), European Galileo and Japanese Quasi-Zenith Satellite System (QZSS) will be presented, based on real data. The combined systems will be evaluated in comparison to the single-systems, for short (atmosphere-fixed) to long (atmosphere-present) baselines. The analysis will consist of the receiver positioning precisions, integer ambiguity success rates, ambiguity/positioning convergence times, and measures of reliability. Reliability is the robustness of the underlying model. It will be shown that the combined systems can provide for improved reliability, ambiguity/positioning convergence times, integer ambiguity resolution and positioning performance over the single-systems. This holds particularly true when higher satellite elevation cut-off angles are used and the ISBs are calibrated, which can be of benefit in environments with restricted satellite visibility such as, e.g., urban canyons, open pit mines or when low-elevation multipath is present.