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Xia et al. Satell Navig (2021) 2:8 Page 18 of 19

Fig. 23, although the bias RMS of BDS in the east direc- environments, because of its good satellite visibility and
tion is greater than GPS, it is smaller in the north and ranging precision. However, in a harsh environment, the
up directions. Tis indicates that once the observation number of BDS satellites tracked by the smartphone is
environment gets better, the kinematic positioning per- susceptible to environmental factors. It is worth noting
formance of BDS will improve signifcantly, even sur- that due to the limitation of smartphone GNSS chipsets,
passing GPS. most of the current smartphones cannot receive the
new BDS-3 signals with higher strength, or even track
Conclusions all the existing BDS satellites, which restricts the obser-
To fully evaluate the performance of BDS positioning vation availability and positioning accuracy of BDS. Te
outside Asia–Pacifc regions for mobile location-based advancement of smartphone hardware in the future
services, the static and kinematic GNSS data in Notting- will inevitably enhance the positioning performance of
ham, UK were collected with Huawei Mate 20 smart- BDS to a new level. Finally, the positioning of BDS inte-
phone. Te tests were conducted in an open meadow grated with other navigation satellite systems can greatly
for static mode and lakeside wooded area for kinematic improve the accuracy and reliability of position solutions.
mode. We estimated the signal carrier-to-noise density
ratio, pseudorange measurement noise, and positioning Acknowledgements
We gratefully acknowledge MGEX and GFZ for providing multi-GNSS orbit
performance of BDS satellites in detail, and compared the products and Dr. Pan Li for sharing the drawing method of global satellite
results with GPS, Galileo and GLONASS. Some major visibility on his public platform. Thank Professor Yongqi Chen and the editor
fndings are summarized as follows: for their careful proofreading which has improved the quality of this manu-
script. The frst author is grateful for the sponsorship of the China Scholarship
Council.
1. BDS can provide location services with good satellite
visibility. BDS has the largest number of nominally Authors’ contributions
Conceptualization, X.M.; methodology, Y.X.; formal analysis, Y.X. and Q.Z.; data
visible satellites in the UK compared to any other sys- curation, Y.X.; writing-original draft preparation, Y.X.; writing-review and edit-
tem. Its signal carrier-to-noise density ratio is com- ing, Y.Y. and W.G.; supervision, S.P. and X.M. All authors read and approved the
parable to GPS. Te signal quality of BDS-3 is gen- fnal manuscript.
erally better than BDS-2 on B1 frequency. Moreover, Funding
the selected BDS satellites have low pseudorange This research was funded by the National Natural Science Foundation of
noise within 0.5 m, which is larger than Galileo satel- China (41774027), the National Key Research and Development Program
(2016YFB0502101), the Postgraduate Research & Practice Innovation Program
lites at 0.23 m level. of Jiangsu Province (KYCX19_0067) and the CoDRIVE demonstration project
2. Te horizontal precision of BDS positioning in an funded under the European Space Agency’s Business Applications initiatives
open environment is better than GPS with the R95 (ESA CoDRIVE Contract Number: 4000126688/19/NL/FGL).
value of 2.88 m, even though its satellite geometry is Availability of data and materials
poorer than GPS. Te high precision using Galileo The smartphone GNSS observations used and analyzed in this study were
is limited by the number of visible satellites, and the collected by the frst author.
positioning results cannot be consistent in the time Competing interests
domain. GLONASS has the worst positioning results The authors declare that they have no confict of interest.
due to its discrepant ranging precision and inter-fre- Author details
quency code bias. Te inclusion of BDS into multi- 1 School of Instrument Science and Engineering, Southeast University,
2
system can signifcantly improve the positioning per- Nanjing 210096, China. Key Laboratory of Micro-Inertial Instrument
formance. and Advanced Navigation Technology, Ministry of Education, Nanjing 210096,
3
China. Nottingham Geospatial Institute, The University of Nottingham,
3. In the complex environment, the kinematic position- Nottingham NG7 2TU, UK. Global Geospatial Engineering Ltd./Sino-UK
4
ing performance of each satellite system degrades Geospatial Engineering Centre, Radford Bridge Road, Nottingham NG8 1NA,
5
due to signal occlusion and refection, but the results UK. State Key Laboratory of Media Convergence Production Technology
6
and Systems, Beijing 100031, China. School of Transportation, Southeast
of GPS are least afected by environmental fac- University, Nanjing 210096, China.
tors. Galileo satellites can rarely be tracked, and the
GLONASS positioning results deteriorate the most. Received: 30 September 2020 Accepted: 2 January 2021
Despite the degradation, the BDS positioning results
are usable for LBS users. In the semi-open area, the
positioning performance of BDS quickly recovers to References
compete with GPS. Banville, S., Lachapelle, G., Ghoddousi-Fard, R., et al. (2019, September).
Automated processing of low-cost GNSS receiver data. In Proceedings of
institute of navigation GNSS+ 2019 conference.
In summary, BDS alone can fully meet the require- Chen, B., Gao, C., Liu, Y., et al. (2019). Real-time precise point positioning with a
ments of global location services, especially in open Xiaomi MI 8 android smartphone. Sensors, 19(12), 2835.