Multi-GNSS precise point positioning with raw single-frequency and dual-frequency measurement models

Abstract

The emergence of multiple satellite navigation systems, including BDS, Galileo, modernized GPS, and GLONASS, brings great opportunities and challenges for precise point positioning (PPP). We study the contributions of various GNSS combinations to PPP performance based on undifferenced or raw observations, in which the signal delays and ionospheric delays must be considered. A priori ionospheric knowledge, such as regional or global corrections, strengthens the estimation of ionospheric delay parameters. The undifferenced models are generally more suitable for single-, dual-, or multi-frequency data processing for single or combined GNSS constellations. Another advantage over ionospheric-free PPP models is that undifferenced models avoid noise amplification by linear combinations. Extensive performance evaluations are conducted with multi-GNSS data sets collected from 105 MGEX stations in July 2014. Dual-frequency PPP results from each single constellation show that the convergence time of undifferenced PPP solution is usually shorter than that of ionospheric-free PPP solutions, while the positioning accuracy of undifferenced PPP shows more improvement for the GLONASS system. In addition, the GLONASS undifferenced PPP results demonstrate performance advantages in high latitude areas, while this impact is less obvious in the GPS/GLONASS combined configuration. The results have also indicated that the BDS GEO satellites have negative impacts on the undifferenced PPP performance given the current ''poor'' orbit and clock knowledge of GEO satellites. More generally, the multi-GNSS undifferenced PPP results have shown improvements in the convergence time by more than 60 % in both the single-and dual-frequency PPP results, while the positioning accuracy after convergence indicates no significant improvements for the dual-frequency PPP solutions, but an improvement of about 25 % on average for the single-frequency PPP solutions.

Consideration of GLONASS Inter-Frequency Code Biases in Precise Point Positioning (PPP) International Time Transfer

“…The GLONASS PPP-based performance in terms of time transfer uncertainty is evaluated at the 68% and 95% confidence levels in the static mode. This statistic approach has been adopted by Lou et al [34] and Zhou et al [13] for assessing PPP performance. The process of the application of the experiments is divided into four part.…”

“…statistic approach has been adopted by Lou et al [34] and Zhou et al [13] for assessing PPP performance. The process of the application of the experiments is divided into four part.…”

National BDS Augmentation Service System (NBASS) of China: Progress and Assessment

“…The processing strategy for real-time single-and dual-frequency PPP is depicted in Figure 3 including BDS and GPS PPP. Based on the generated PPP model with raw observations in [21], the PANDA software is modified for real-time single-and dual-frequency PPP. The ionosphere-free observation is used in dual-frequency PPP, while the single-frequency PPP is based on the raw observations and the real-time ionospheric corrections are used in PPP as a priori constraint.…”

“…In our real-time PPP processing, the weight of BDS GEOs is one third that of other satellites. For more information about the PPP model, we refer to [10,21]. The ionospheric STEC (slant total electron content) can often be calculated by using phasesmoothed pseudorange observations and the VTEC is modeled in a solar-geomagnetic reference frame by using spherical harmonic models.…”

“…In our real-time PPP processing, the weight of BDS GEOs is one third that of other satellites. For more information about the PPP model, we refer to [10,21]. …”