Precise Point Positioning with Ambiguity Resolution for Different Signals
My Master’s thesis at the Institute for Astronomical and Physical Geodesy (IAPG) of Technical University of Munich (TUM), under the supervision of Prof. Urs Hugentobler and Dr. Bingbing Duan.
Carrier-phase integer ambiguity resolution (AR) is the key to the fast and high-precision GNSS positioning and navigation. To make use of undifferenced GNSS observations for precise point positioning applications, the method of Zero-difference Ambiguity Resolution is proposed, developed, and now being widely applied in precise GNSS studies. Many researchers and groups have investigated various realization approaches by means of generating GNSS satellite biases, orbit and clock products for PPP users. TUM, as one of the IGS MGEX analysis centers, is also estimating such precise satellite products in their strategy. The theoretical background of both TUM and CNES approaches are introduced and compared in this thesis.
In order to demonstrate the feasibility of TUM’s GPS and Galileo products, a series of PPP-AR experiments are designed and conducted. In addition, this thesis also studies on the difference of GNSS signals (GPS L1-L2, Galileo E1-E5a and Galileo E1-E5b), as well as of different observation types (Q and X) from individual signals in the positioning domain. A validation tool named inter-strategy consistency rate is proposed and developed based on previous studies and applied in the experiments for two groups of satellite products (TUM and CNES).
Experiment results and their validations illustrate the PPP and PPP-AR performances as well as their comparisons of all GNSS signals and of all satellite products. GPS is found to generally reach better PPP accuracy than Galileo signals, while Galileo benefits more in the improvement percentages from the Zero-difference Ambiguity Resolution (i.e. 13% for north, 36% for east and 11% for up direction). In view of the ambiguity resolution quality, Galileo signals also have higher wide-lane and narrow-lane fixing rates. The observation types Q and X shows very little differences in the PPP-AR results with slightly advantage in Type X. Finally, the comparison of TUM and CNES products are conducted and a 94% consistency rate for GPS and 85% for Galileo are obtained. CNES products performs slightly better for GPS signals but not successfully worked for Galileo observations in this study.