Application of slant total electron content obtained from the computerized ionospheric tomography for Precise Point Positioning (PPP)

The undifferenced and uncombined precise point positioning (UPPP) method preserves ionospheric parameters as estimable variables, this methodology facilitates the integration of external ionospheric constraints. In this study, we employ ionospheric tomography technology to obtain high-precision ionospheric products that are applied to UPPP in the forms of slant total electron content (STEC) (PPP-CIT-STEC) and vertical total electron content (VTEC) (PPP-CIT-VTEC). In addition, the UPPP approach incorporates the 2-dimensional VTEC model (PPP-2D-VTEC). The positioning performance of these three UPPP methods is compared and analyzed. Using observation data from the United States and Hunan Province, experiments were conducted for GPS UPPP and BDS UPPP. The findings revealed that PPP-CIT-STEC significantly outperformed PPP-2D-VTEC and PPP-CIT-VTEC, achieving improvements in positioning accuracy of more than 20% and 12%, and in convergence performance of more than 25% and 13%, respectively. During the geomagnetic storm, PPP-CIT-STEC also demonstrated remarkable robustness. This research highlights the efficacy of high-precision ionospheric products in enhancing the performance of UPPP, while also mitigating the influence of mapping functions on positioning outcomes in the computation of ionospheric delays within UPPP.