The implementation of Intelligent Transport System (ITS) technology is expected to significantly improve road safety and traffic efficiency. 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 flexibility. However, GNSS PPP is vulnerable to several effects, especially those caused by the challenging 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 different groups according to their impact and error sources to assist integrity fault analysis, which is demonstrated with Failure Modes and Effects Analysis (FMEA) and Fault Tree Analysis (FTA) methods. The main vulnerabilities are discussed 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 briefly reviewed. Both system-level (network-end) and user-level (user-end) integrity monitoring approaches for PPP are briefly discussed, focusing on their development and the challenges in urban scenarios. Some open issues, on which further efforts should focus, are also identified.

中文翻译：

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智能交通系统精确点定位的漏洞和完整性：概述和分析

智能交通系统（ITS）技术的实施有望大大改善道路安全和交通效率。ITS的关键组件之一是精确的车辆定位。分米定位到亚米精度是自动驾驶和其他自动应用程序的基本功能。全球导航卫星系统（GNSS）的精确点定位（PPP）由于其相对较低的成本和灵活性而成为ITS的一种有吸引力的定位方法。但是，GNSS PPP容易受到多种影响，尤其是在极有可能需要ITS技术的充满挑战的城市环境所造成的影响中。为了满足ITS应用程序的高度完整性要求，有必要仔细分析PPP的潜在故障和失败并研究相关的完整性监视方法。本文概述了GNSS PPP的漏洞，以识别开发PPP完整性监控方法时需要监控的故障。这些漏洞根据其影响和错误源分为不同的组，以帮助进行完整性故障分析，这可以通过故障模式和影响分析（FMEA）和故障树分析（FTA）方法得到证明。详细讨论了主要漏洞，以及它们的原因，特征，对用户的影响以及相关的缓解方法。另外，简要回顾了用于解决ITS应用中PPP中的威胁和故障的完整性监视方法的研究。简要讨论了PPP的系统级（网络端）和用户级（用户端）完整性监控方法，关注他们的发展以及城市情景中的挑战。还确定了一些未解决的问题，应将其作为进一步工作的重点。