Article
Assessment of GPS/Galileo/BDS Precise Point Positioning with
Ambiguity Resolution Using Products from Different
Analysis Centers
Chao Chen
1,2
, Guorui Xiao
3
, Guobin Chang
1,2,
* , Tianhe Xu
4
and Liu Yang
1,2
Citation: Chen, C.; Xiao, G.; Chang,
G.; Xu, T.; Yang, L. Assessment of
GPS/Galileo/BDS Precise Point
Positioning with Ambiguity
Resolution Using Products from
Different Analysis Centers. Remote
Sens. 2021, 13, 3266. https://doi.org/
10.3390/rs13163266
Academic Editor: Damian Wierzbicki
Received: 2 July 2021
Accepted: 15 August 2021
Published: 18 August 2021
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Attribution (CC BY) license (https://
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4.0/).
1
NASG Key Laboratory of Land Environment and Disaster Monitoring, China University of Mining
and Technology, Xuzhou 221116, China; cchen@cumt.edu.cn (C.C.); ylliuyang@yeah.net (L.Y.)
2
School of Environmental Science and Spatial Informatics, China University of Mining and Technology,
Xuzhou 221116, China
3
Zhengzhou Institute of Surveying and Mapping, Zhengzhou 450052, China; xgr@whu.edu.cn
4
Institute of Space Science, Shangdong University, Weihai 264209, China; thxu@sdu.edu.cn or
thxugfz@163.com
* Correspondence: guobinchang@hotmail.com
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.
Keywords: multi-GNSS; PPP; ambiguity resolution (AR); analysis center
1. Introduction
Precise point positioning (PPP) is an absolute positioning technology that can oper-
ate on a global scale [
1
–
3
] and it is widely acknowledged as a promising approach for
crustal deformation monitoring [
4
,
5
], GPS meteorology [
6
], high-accuracy kinematic po-
sitioning [
7
,
8
], and regional seismic activity monitoring [
9
]. However, 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
Remote Sens. 2021, 13, 3266. https://doi.org/10.3390/rs13163266 https://www.mdpi.com/journal/remotesensing
