In order to fully exploit the advantages of both precise point positioning (PPP) and real-time kinematic (RTK), a PPP–RTK method has been proposed to achieve centimeter-level positioning by applying the rapid integer ambiguity resolution, which is now widely implemented in some commercial systems such as Trimble RTX-Fast and NavCom StarFire. Nevertheless, the performance of PPP–RTK faces with restrictions under the circumstance of urban environments due to intermittent signal interruptions and unfavorable tracking geometry. Presently, it is increasingly prevalent that the inertial navigation system (INS) is integrated with global navigation satellite system (GNSS) to serve for enhancing the positioning performance. In this contribution, a tightly coupled PPP–RTK/INS integration model is developed, aiming to provide continuous and precise positioning service under the complex urban environments. In the proposed model, the precise atmospheric corrections derived from the multi-GNSS PPP fixed solutions of reference stations are disseminated to users to enable the rapid ambiguity resolution in PPP–RTK/INS. Furthermore, the high-accuracy position information offered by INS is also used to enhance the performance of ambiguity fixing. Experiments in different scenarios of urban roads and overpasses were designed to verify the effectiveness of the proposed method. Results indicate that the solution availability, fixing percentage and positioning accuracy can be significantly improved by PPP–RTK/INS integration. The horizontal positioning accuracy of the tightly coupled PPP–RTK/INS is 1–2 cm in a semi-urban environment and 5–6 cm in a real urban environment with a fixing percentage of 90.7% and 81.2%, respectively. Moreover, INS information also shows capability of bridging the gaps in GNSS data, which enables continuous positioning and fast ambiguity re-fixing under the GNSS-challenged environments. A fast ambiguity recovery within 1–5 s could be achieved for PPP–RTK/INS after outages lasting up to 30 s, while 8–18 s is required for PPP–RTK.

为了充分发挥精确点定位（PPP）和实时运动学（RTK）的优势，提出了一种PPP-RTK方法，通过应用快速整数模糊度分辨率实现厘米级定位，目前已被广泛应用。在一些商业系统中实现，例如 Trimble RTX-Fast 和 NavCom StarFire。然而，由于间歇性信号中断和不利的跟踪几何形状，PPP-RTK 的性能在城市环境的情况下面临限制。目前，惯性导航系统（INS）与全球导航卫星系统（GNSS）集成以提高定位性能的做法越来越普遍。在这个贡献中，开发了一个紧密耦合的 PPP-RTK/INS 集成模型，旨在在复杂的城市环境下提供连续、精准的定位服务。在所提出的模型中，来自参考站的多 GNSS PPP 固定解的精确大气校正被传播给用户，以实现 PPP-RTK/INS 中的快速模糊度解决。此外，INS 提供的高精度位置信息也用于提高模糊度修复的性能。设计了城市道路和立交桥不同场景下的实验来验证所提出方法的有效性。结果表明，PPP-RTK/INS 集成可以显着提高解决方案的可用性、固定百分比和定位精度。紧耦合PPP-RTK/INS的水平定位精度在半城市环境中为1-2 cm，在真实城市环境中为5-6 cm，固定百分比分别为90.7%和81.2%。此外，INS 信息还显示了弥合 GNSS 数据差距的能力，从而能够在 GNSS 挑战的环境下实现连续定位和快速模糊重新修复。PPP-RTK/INS 在中断长达 30 秒后可以在 1-5 秒内实现快速模糊恢复，而 PPP-RTK 需要 8-18 秒。