Page 34 - 卫星导航2021年第1-2合期

Du et al. Satell Navig (2021) 2:3 Satellite Navigation
https://doi.org/10.1186/s43020-020-00034-8
https://satellite-navigation.springeropen.com/

REVIEW Open Access

Vulnerabilities and integrity of precise point

positioning for intelligent transport systems:

overview and analysis

1*
1
1
Yujun Du , Jinling Wang , Chris Rizos and Ahmed El‑Mowafy 2

Abstract
The implementation of Intelligent Transport System (ITS) technology is expected to signifcantly improve road safety
and trafc efciency. One of the key components of ITS is precise vehicle positioning. Positioning with decimetre to
sub‑metre accuracy is a fundamental capability for self‑driving, and other automated applications. Global Navigation
Satellite System (GNSS) Precise Point Positioning (PPP) is an attractive positioning approach for ITS due to its relatively
low‑cost and fexibility. However, GNSS PPP is vulnerable to several efects, especially those caused by the challeng‑
ing urban environments, where the ITS technology is most likely needed. To meet the high integrity requirements of
ITS applications, it is necessary to carefully analyse potential faults and failures of PPP and to study relevant integrity
monitoring methods. In this paper an overview of vulnerabilities of GNSS PPP is presented to identify the faults that
need to be monitored when developing PPP integrity monitoring methods. These vulnerabilities are categorised into
diferent groups according to their impact and error sources to assist integrity fault analysis, which is demonstrated
with Failure Modes and Efects Analysis (FMEA) and Fault Tree Analysis (FTA) methods. The main vulnerabilities are dis‑
cussed in detail, along with their causes, characteristics, impact on users, and related mitigation methods. In addition,
research on integrity monitoring methods used for accounting for the threats and faults in PPP for ITS applications is
briefy reviewed. Both system‑level (network‑end) and user‑level (user‑end) integrity monitoring approaches for PPP
are briefy discussed, focusing on their development and the challenges in urban scenarios. Some open issues, on
which further eforts should focus, are also identifed.
Keywords: Intelligent transport system, GNSS precise point positioning, Vulnerability, Fault analysis, Integrity
monitoring

Introduction Positioning Service (SPS) using L1 coarse/acquisition
Intelligent Transport System (ITS) technology relies on (C/A) code observations results in a horizontal position
one or more Global Navigation Satellite Systems (GNSS) error of the order of 5–10 m (at 95% probability), which
for absolute positioning (Dovis et al. 2020; Firmin 2006; is insufciently accurate for critical ITS applications (U.S.
Imparato et al. 2018b). What is required is a low-cost Department of Defense 2020). Te possible GNSS posi-
positioning technique for decimetre to sub-metre accu- tioning techniques that can be used in ITS include Real-
racy, with real-time capability to enable automated Time Kinematic (RTK) and Network RTK (NRTK), use
vehicle navigation (Green et al. 2013; Stephenson et al. of a Satellite Based Augmentation System (SBAS), and
2011). Te GPS (Global Positioning System) Standard Precise Point Positioning (PPP) (Green et al. 2013; Lovas
et al. 2011).
RTK and NRTK are both diferential positioning tech-
*Correspondence: yujundu@sdu.edu.cn
1 School of Civil and Environmental Engineering, University of New South niques which require one or more nearby continuously
Wales, Sydney, Australia operating GNSS reference station. In contrast, PPP is
Full list of author information is available at the end of the article an absolute positioning technique that can be applied

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