Abstract:

[Objective] Ambiguity resolution (AR) plays a key role in achieving fast and high-precision positioning of the Global Navigation Satellite System (GNSS). This paper implements the precise point positioning (PPP) ambiguity resolution based on the uncombined model. [Methods] By applying Singularity-basis theory, the rank deficiencies between integer ambiguities and phase biases are fully eliminated through choosing appropriate bases, thus the satellite phase biases (SPBs) can be effectively separated from ambiguities and accurately estimated from a GNSS network, and reliable integer ambiguity resolution enabled PPP is naturally fulfilled. [Results] We succeed in recovering the property of the user-end ambiguities to a natural integer with the aid of SPB corrections estimated by a regional reference network, resulting in substantial improvement in positioning performance. Compared to the ambiguity float solution, the three-dimensional convergence time of the ambiguity fixed solution decreased from 68, 28, and 33 minutes to 28.5, 21.5, and 26.5 minutes, and the positioning accuracy improved by 49%, 40%, and 22% respectively. [Conclusions] The ambiguity resolution algorithm based on the uncombined PPP model is crucial for the fast and high-precision positioning of GNSS.

Key words: precise point positioning, uncombined model, satellite phase bias, ambiguity resolution