Single-epoch PPP-RTK with Multi-Frequency Multi-Constellation: Reliable and Instantaneous Centimeter-level User Positioning

The demand for fast and high-precision spatiotemporal information has increasingly grown in recent years, particularly in fields such as autonomous driving and other safety-related applications. The single-epoch Precise Point Positioning (PPP) technique proves particularly advantageous in complex and dynamic application environments due to its property of fast-available solutions, no need for cycle slip detection, and robust interference resistance. Considering only extra-wide-lane (EWL) and wide-lane (WL) ambiguities are fixed in most existing single-epoch research, this study proposes to incorporate regional atmospheric corrections to further enhance the WL ambiguity resolution (WAR) solutions. Firstly, the atmospheric interpolation errors were assessed using three public networks with different average inter-station distances, which are the National Oceanic and Atmospheric Administration (NOAA), EUREF Permanent GNSS Network (EPN), and Geoscience Australia (GA). Results showed that the interpolated tropospheric zenith wet delay errors were within 1 cm, while the interpolated ionospheric errors were more related to inter-station distances, with the longest distance (EPN) of ∼150 km showing errors of 4.5 cm, and others below 4.0 cm. Three single-epoch solutions were designed for both triple- and five-frequency observations, namely PPP-FLOAT-3/5, PPP-WAR-3/5 (solution in most existing research), and PPP-RTK-3/5 (proposed method), depending on whether WAR was performed or atmospheric corrections were applied. The proposed single-epoch PPP-RTK method achieved the best performance in terms of positioning accuracy and AR success rate for both static solutions and vehicle experiments. For all processed static stations, the PPP-RTK-3 positioning errors were 4.2 cm,4.7 cm, and 10.1 cm for east, north, and up, respectively, representing improvements of 77.2%, 82.1%, and 79.7% compared with PPP-WAR-3 solutions. Introducing atmospheric corrections also improved the WL AR success rate from 96.9% to 99.0%, indicating more reliable and accurate solutions with the proposed method. Realistic vehicle experiments further confirmed the effectiveness of the proposed method, with the positioning errors reduced from 84.3 cm, 56.8 cm, and 33.8 cm (FLOAT-3) to 9.1 cm, 8.6 cm, and 18.5 cm in the east, north, and up directions, respectively. The introduction of five-frequency measurements further improved the positioning performance. For static stations, the proportion of epochs with horizontal errors below 10 cm reached 89.1%, while those below 30 cm rose to 98.6%. In dynamic vehicular experiments, PPP-RTK-5 achieved accuracies of 8.4 cm, 7.8 cm, and 18.1 cm in the east, north, and up components, respectively. The results obtained in this study demonstrate the effectiveness and potential of the proposed single-epoch solution in applications in which instantaneous decimeter-level positioning accuracy is needed.