Sunil B BisnathAdu, Benjamin2025-07-232025-07-232025-03-262025-07-23https://hdl.handle.net/10315/42978Achieving instantaneous centimetre-level 3D accuracy for Global Navigation Satellite System (GNSS) multi-constellation, multi-frequency Precise Point Positioning (PPP) with ambiguity resolution without local augmentation poses significant challenges due to multipath, atmospheric refraction, and hardware noise. This research reduces York-PPP engine limitations by separating the BeiDou-2 and BeiDou-3 GNSS constellations clock terms in the design matrix and expanding the uncombined Decoupled Clock Model from triple to quadruple frequency measurements for BeiDou-3 constellation. Processing of geodetic measurements show overall horizontal positioning errors reduced by 77% (from 20.8 cm to 4.7 cm) and 88% (from 22.8 cm to 2.8 cm) for float and fixed solutions, respectively. Furthermore, this research investigates outliers in epoch-by-epoch PPP solutions, delving into potential causes such as signal-to-noise ratio (SNR), pseudorange multipath and noise etc. Additionally, principal component analysis with Hotelling’s T-squared method is employed to detect major outlier sources. Results indicate that satellite elevation angle, signal strength, and the code-minus-carrier observable, which includes ionospheric refraction and pseudorange multipath, significantly impact positioning solution.Author owns copyright, except where explicitly noted. Please contact the author directly with licensing requests.Geographic information science and geodesyElectronic Thesis or Dissertation2025-07-23Global Navigation Satellite SystemPrecise Point PositioningMulti-ConstellationMulti-FrequencyAmbiguity ResolutionPrincipal Component AnalysisDecoupled Clock Model