Near real-time multi-GNSS orbits, clock and observable-specific biases at Wuhan University

Precise orbit, clock and observable-specific phase bias products play a pivotal role in facilitating precise point positioning (PPP) with ambiguity resolution (AR). The model and strategy used to generate Wuhan University Multi-GNSS (WUM) hourly updated ultra-rapid products is summarized in this study. A refined iteration of the block-to-block operation method is introduced, which demonstrates a substantial increase in efficiency, achieving enhancements of 13-fold and 29-fold for Central Processing Unit and Graphics Processing Unit platforms, respectively. Subsequently, a pre-integration approach is introduced for numerical orbit integration, resulting in a noticeable improvement of efficiency ranging from 6 to 28 times. To enhance the solution strength and precision, a single-differenced-based ambiguity fixing method is explored in our routine processing, which improves for all the satellites, except for GLONASS, and multi-GNSS products are released with a 1-h latency. The orbit assessment is conducted through a comparative analysis with International GNSS Service (IGS) and the Wuhan University Multi-GNSS Combined orbits. The three-dimensional precision of the near real-time orbits reaches 2.4 cm, 4.6 cm, 3.8 cm, and 4.9 cm for GPS, GLONASS, Galileo, and BDS3 MEO satellites, respectively. Regarding IGSO satellites of BDS and QZSS, the corresponding values range between 11.4 cm and 15.7 cm. In contrast, the GEOs of BDS and QZSS exhibit comparatively inferior performance, demonstrating consistencies of 234.7 cm and 70.9 cm, respectively. The validation of the near real-time products is performed utilizing PPP-AR. The statistical analysis across a global network of 340 stations with 20 days reveals a wide-lane fixing rate exceeding 91.1% for multi-GNSS, accompanied by a narrow-lane fixing rate of approximately 97.0%. The PPP-AR solution demonstrates the accuracy of 1.6 mm, 1.7 mm, and 5.0 mm in the east, north, and up directions for IGS weekly solutions, respectively. The results are promising and further confirm that the products are effective.