Equatorial plasma bubbles (EPBs) occur frequently in low-latitude areas and have a non-negligible impact on navigation satellite signals. To systematically analyze the effects of a single EPB event on multi-frequency signals of GPS, Galileo, GLONASS, and BDS, all-sky airglow images over South China are jointly used to visually determine the EPB structure and depletion degree. The results reveal that scintillations, or GNSS signal fluctuations, are directly linked to EPBs and that the intensity of scintillation is positively correlated with the airglow depletion intensity. The center of the airglow depletion often corresponds to stronger GNSS scintillation, while the edge of the bubble, which is considered to have the largest density gradient, corresponds to relatively smaller scintillation instead. This work also systematically analyzes the responses of multi-constellation and multi-frequency signals to EPBs. The results show that the L2 and L5 frequencies are more susceptible than the L1 frequency is. For different constellations, Galileo’s signal has the best tracking stability during an EPB event compared with GPS, GLONASS, and BDS. The results provide a reference for dual-frequency signal selection in precise positioning or TEC calculation, that is, L1C and L2L for GPS, L1C and L5Q for Galileo, L1P and L2C for GLONASS, and L1P and L5P for BDS. Notably, BDS-2 is significantly weaker than BDS-3. And inclined geosynchronous orbit (IGSO) satellites have abnormal data error rates, which should be related to the special signal path trajectory of the IGSO satellite.

BeiDou Satellite Based Augmentation System (BDSBAS) can notably improve the GNSS L1 positioning performance by transmitting the orbit, clock and ionosphere corrections. Aside from terrestrial geodetic receivers, the mass-market smartphones also benefit from the augmentation service. In this paper, the smartphone-based GPS-L1 standard point positioning (SPP) augmented by BDSBAS corrections is analyzed using Huawei-P40 smartphone. The quality of BDSBAS-B1C ionospheric information is evaluated by ionospheric observables retrieved from the selected 20 stations. Compared to the BDS-3 global ionosphere model (BDGIM) and the Global Ionosphere Maps (GIM) of the International GNSS Service (IGS), the accuracy of BDSBAS ionospheric correction is about 28% better than BDGIM and 11% better than the IGS-GIM. Compared to the GPS-L1 SPP, the accuracy of BDSBAS augmented smartphone positioning increases by 27% in the horizontal component and 41% in vertical component in the open-sky environment, and 50% improvement in both directions in the second experiment where the smartphone connects with an external geodetic GNSS antenna to reduce the negative effects of multipath errors.

This article discusses outcomes of the Polish–Chinese project dedicated to establishing multi-GNSS near-real-time ionospheric services. ARTEMIS (Advanced methodology development for Real-Time Multi-constellation (BDS, Galileo and GPS) Ionosphere Services) was a response to increasing GNSS data availability, including Galileo and BeiDou observations on the one hand and growing interest in high-quality ionospheric products on the other. The project resulted in elaborating methodologies to monitor the ionospheric Total Electron Content (TEC) and its fluctuations (ROTI index) based on a full multi-GNSS approach and establishing pilot real-time web services in a global and regional approach. The project’s outcomes are to be included in the International GNSS Service (IGS) and International Reference Ionosphere (IRI) in the near future. This article presents real-time ionospheric products developed under the ARTEMIS project and evaluates their performance using independent techniques such as DORIS observations and altimetry with regard to other existing products. The Discussion section also includes an evaluation of ARTEMIS products in positioning applications.