###### Abstract  
The long convergence time and non-robust positioning accuracy are the main factors limiting the application of precision single-point positioning (PPP) in kinematic vehicle navigation. Therefore, a dual/triple-frequency multi-constellation PPP-RTK method with atmospheric augmentation is proposed to achieve cm-level reliable kinematic positioning. The performance was assessed using a set of static station and kinematic vehicle positioning experiments conducted in Wuhan. In the static experiments, instantaneous convergence within 1 s and centimeter-level positioning accuracy were achieved for PPP-RTK using dual-frequency observation. For the kinematic experiments, instantaneous convergence was also achieved for dual-frequency PPP-RTK in open areas, with RMS of 2.6 cm, 2.6 cm, and 7.5 cm in the north, east, and up directions, respectively, with accuracy similar to short-baseline real-time kinematic positioning (RTK). Horizontal positioning errors of less than 0.1 m and 3D positional errors of less than 0.2 m were 99.54% and 98.46%, respectively. Additionally, after the outage of GNSS and during satellite reduction in obstructed environments, faster reconvergence and greater accuracy stability were realized compared with PPP without atmospheric enhancement. Triple-frequency PPP-RTK was able to further enhance the robustness and accuracy of positioning, with RMS of 2.2 cm, 2.0 cm, and 7.3 cm, respectively. In summary, a performance similar to RTK was achieved based on dual-frequency PPP-RTK, demonstrating that PPP-RTK has the potential for lane-level navigation. GNSS; PPP-RTK; atmospheric augmentation; vehicle navigation +
Footnote †: journal: Remote Sens. 20241628  
PPP-RTK was first proposed by [7]; it fully integrates the advantages of rapid ambiguity resolution for RTK and flexibility for PPP. At the same time, it avoids their drawbacks, such as heavy communication burdens and low positioning efficiency [8]. PPP-RTK is based on precise satellite orbit, clock, signal bias, and optional atmospheric products estimated through the use of a regional reference station network. Currently, PPP-RTK can achieve ambiguity resolution via the calibration of satellite phase bias products via different methods [9; 10; 11]. Considering that atmospheric error is the key factor affecting the convergence of PPP, using precise atmospheric products, such as ionospheric delay and tropospheric conditions provided by the ground station network, the convergence time of PPP-RTK can be further shortened [12; 13]. PPP-RTK can provide unified and seamless positioning services, placing it at the forefront of research. For example, [14] proposed a PPP-RTK model that reparametrizes network parameters, such as phase biases and atmospheric delays, which are then applied to correct observations for users to achieve ambiguity resolution. A PPP-RTK model using undifferenced augmentation corrections was proposed by [9; 15]. In this method, the precise satellite orbit and clock, phase bias, and atmospheric enhancement corrections are generated at the undifferenced level. With the development of multi-GNSS, PPP-RTK research has progressed from an ionosphere-free model to undifferenced and uncombined models [16; 17], single systems to multi-systems [12; 18; 19], and single-frequency or dual-frequency designs to multi-frequency designs [20; 21]. Building on the progress made in theoretical research, multiple research institutions and commercial companies have developed PPP-RTK service systems to provide real-time precise positioning services on a global scale. For example, Japan has established a regional PPP-RTK service, the Centimeter-Level Augmentation Service (CLAS), which is based on the L6D signal of the Quasi-Zenith Satellite System (QZSS) [22]. Additionally, several commercial companies have begun offering PPP-RTK services, including Trimble with its RTX service, NovAtel with the TerraStar-X service, and GEO++ with the SSRPOST service.