Page 187 - 卫星导航2021年第1-2合期

Li et al. Satell Navig (2021) 2:1 Satellite Navigation
https://doi.org/10.1186/s43020-020-00033-9
https://satellite-navigation.springeropen.com/

ORIGINAL ARTICLE Open Access

Semi-tightly coupled integration

of multi-GNSS PPP and S-VINS for precise

positioning in GNSS-challenged environments

*
Xingxing Li , Xuanbin Wang, Jianchi Liao, Xin Li, Shengyu Li and Hongbo Lyu

Abstract
Because of its high-precision, low-cost and easy-operation, Precise Point Positioning (PPP) becomes a potential and
attractive positioning technique that can be applied to self-driving cars and drones. However, the reliability and
availability of PPP will be signifcantly degraded in the extremely difcult conditions where Global Navigation Satel-
lite System (GNSS) signals are blocked frequently. Inertial Navigation System (INS) has been integrated with GNSS to
ameliorate such situations in the last decades. Recently, the Visual-Inertial Navigation Systems (VINS) with favorable
complementary characteristics is demonstrated to realize a more stable and accurate local position estimation than
the INS-only. Nevertheless, the system still must rely on the global positions to eliminate the accumulated errors. In
this contribution, we present a semi-tight coupling framework of multi-GNSS PPP and Stereo VINS (S-VINS), which
achieves the bidirectional location transfer and sharing in two separate navigation systems. In our approach, the local
positions, produced by S-VINS are integrated with multi-GNSS PPP through a graph-optimization based method.
Furthermore, the accurate forecast positions with S-VINS are fed back to assist PPP in GNSS-challenged environments.
The statistical analysis of a GNSS outage simulation test shows that the S-VINS mode can efectively suppress the
degradation of positioning accuracy compared with the INS-only mode. We also carried out a vehicle-borne experi-
ment collecting multi-sensor data in a GNSS-challenged environment. For the complex driving environment, the PPP
positioning capability is signifcantly improved with the aiding of S-VINS. The 3D positioning accuracy is improved by
49.0% for Global Positioning System (GPS), 40.3% for GPS + GLOANSS (Global Navigation Satellite System), 45.6% for
GPS + BDS (BeiDou navigation satellite System), and 51.2% for GPS + GLONASS + BDS. On this basis, the solution with
the semi-tight coupling scheme of multi-GNSS PPP/S-VINS achieves the improvements of 41.8–60.6% in 3D position-
ing accuracy compared with the multi-GNSS PPP/INS solutions.
Keywords: Multi-GNSS PPP, Visual-inertial odometry, Multi-sensor fusion, GNSS-challenged environment,
Autonomous driving

Introduction System (BDS) and European Galileo navigation satel-
Precise Point Positioning (PPP) has been demonstrated lite system (Galileo) brings new opportunities for PPP. A
as an efective tool in high-precision positioning and four-system PPP model was proposed by Li et al. (2015)
shows the advantages of efciency and fexibility com- to fully use the Global Positioning System (GPS), Global
pared to the baseline network approach (Zumberge et al. Navigation Satellite System (GLONASS), Galileo, and
1997; Bisnath and Gao 2009). In recent years, the rapid BDS observations. In their study, the multi-constella-
development of Chinese BeiDou navigation satellite tion Global Navigation Satellite System (GNSS) PPP
presented faster solution convergence and higher posi-
tioning accuracy than single-system PPP. Recently, the
*Correspondence: xxli@sgg.whu.edu.cn
School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, investigation of multi-GNSS PPP data processing is not
Wuhan 430079, China only about the dual-frequency models (Cai et al. 2015),

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