Robust, Multi-Constellation, Multi-Frequency Precise Point Positioning For Instantaneous cm-level Positioning

Achieving 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.