Abstract
Suffering from hardware phase biases originating from satellites and the receiver, precise point positioning (PPP) requires a long convergence time to reach centimeter coordinate accuracy, which is a major drawback of this technique and limits its application in time-critical applications. Ambiguity resolution (AR) is the key to a fast convergence time and a high-precision solution for PPP technology and PPP AR products are critical to implement PPP AR. Nowadays, various institutions provide PPP AR products in different forms with different strategies, which allow to enable PPP AR for Global Positioning System (GPS) and Galileo or BeiDou Navigation System (BDS). To give a full evaluation of PPP AR performance with various products, this work comprehensively investigates the positioning performance of GPS-only and multi-GNSS (Global Navigation Satellite System) combination PPP AR with the precise products from CNES, SGG, CODE, and PRIDE Lab using our in-house software. The positioning performance in terms of positioning accuracy, convergence time and fixing rate (FR) as well as time to first fix (TTFF), was assessed by static and kinematic PPP AR models. For GPS-only, combined GPS and Galileo PPP AR with different products, the positioning performances were all comparable with each other. Concretely, the static positioning errors can be reduced by 21.0% (to 0.46 cm), 52.5% (to 0.45 cm), 10.0% (to 1.33 cm) and 21.7% (to 0.33 cm), 47.4% (to 0.34 cm), 9.5% (to 1.16 cm) for GPS-only and GE combination in north, east, up component, respectively, while the reductions are 20.8% (to 1.13 cm), 42.9% (to 1.15 cm), 19.9% (to 3.4 cm) and 20.4% (to 0.72 cm), 44.1% (to 0.66 cm), 10.1% (to 2.44 cm) for kinematic PPP AR. Overall, the positioning performance with CODE products was superior to the others. Furthermore, multi-GNSS observations had significant improvements in PPP performance with float solutions and the TTFF as well as the FR of GPS PPP AR could be improved by adding observations from other GNSS. Additionally, we have released the source code for multi-GNSS PPP AR, anyone can freely access the code and example data from GitHub.
Highlights
Precise point positioning (PPP) is an absolute positioning technology that can operate on a global scale [1,2,3] and it is widely acknowledged as a promising approach for crustal deformation monitoring [4,5], Global Positioning System (GPS) meteorology [6], high-accuracy kinematic positioning [7,8], and regional seismic activity monitoring [9]
The best overall performance from Center for Orbit Determination in Europe (CODE) may be attributed to the adoption of an update solar radiation pressure (SPR) model
The realization of precise point positioning (PPP) Ambiguity resolution (AR) depends on the phase bias products
Summary
The undifferenced ambiguities (UAs) estimated in the conventional PPP model cannot be resolved to an integer value due to the phase biases (or uncalibrated phase delay (UPD) or fractional. 2021, 13, 3266 cycle bias (FCB)) originating from both receiver- and satellite-dependent hardware delay (hereafter collectively referred to as UPD) that are absorbed into the UAs. the integer property of UAs is destroyed. PPP accuracy, especially for the east component, is worse than that of the relative positioning [10,11], and it is only able to achieve a positional accuracy of 10 cm after a convergence time of 30 min [12]
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