## 6 Conclusions  
In this paper, the observations from Huawei Mate40, P40 and geodetic receivers are used, and real-time orbit and clock offset products are applied to conduct smartphone PPP. The following conclusions are drawn:  
1. The positive correlation between C/N0 and elevation is not found, the C/N0 of some observations is low at a higher elevation, and the degree of dispersion for smartphone C/N0 is larger than that of geodetic receivers. The C/N0 of GPS is the best, with an average value of 35 dB-Hz; the results of BDS and GLONASS are the second, with an average of 33 dB-Hz; the result of Galileo is the worst, with an average of 30 dB-Hz. 2. The total number of satellites that can be observed by Huawei Mate40 and P40 is around 30. The number of tracked BDS satellites of the smartphone is larger than that of the GPS, while the GLONASS and Galileo system is relatively small. The PDOP of the Huawei P40 is slightly better than that of the Mate40, the smartphone PDOP of GPS shows the worst, while the average PDOP of BDS, GPS/BDS, GPS/BDS/GLONASS and GPS/BDS/GLONASS/Galileo combinations is less than 1.8. 3. In terms of real-time orbit accuracy: the accuracy of most GPS and Galileo satellites is better than 0.05 m and 0.1 m in along, cross and radial directions, respectively. Different GLONASS satellites have smaller differences in along and cross directions, but the accuracy in the radial direction is larger. In terms of real-time clock offset accuracy: the clock offset accuracy of GPS and Galileo satellites is better than 0.15 and 0.25 ns, respectively. Compared with BDS-2, the clock offset accuracy of the BDS-3 satellite has been significantly improved, and is better than 0.28 ns, while the clock offset accuracy of the GLONASS satellite is better than 0.8 ns. 4. In terms of real-time static PPP, the smartphone can achieve decimeter-level PPP accuracy after convergence. The GPS/BDS/Galileo combination of Huawei P40 shows the best PPP accuracy in three components, with RMS of 0.09, 0.27 and 0.12 m in the east, north and up components, respectively. Moreover, in terms of real-time kinematic PPP, there is a large difference between the PPP accuracy of smartphones and receivers, and kinematic, real-time PPP can achieve meter-level positioning accuracy. The GPS/BDS/Galileo combination of Huawei P40 presented the best PPP accuracy, with 3.88, 3.39 and 7.83 m in the E, N and U components, respectively. In summary, there is a need for further development of real-time PPP for smartphones, but it is currently limited by the quality of the observation data. Hence, it is possible to achieve better real-time PPP accuracy by fusing positioning with multiple sensors to solve the drawbacks of single positioning in the future. [PERSON] and [PERSON] conceived and designed these experiments and wrote this paper; [PERSON], [PERSON], [PERSON] and [PERSON] performed the experiments, analyzed the data, drew pictures, and wrote this paper. All authors have read and agreed to the published version of the manuscript. This work was supported by the Programs of the National Natural Science Foundation of China (42127802), the Key R&D Program of Shaanxi Province (2022 ZDLSF07-12), the Special Fund for Basic Scientific Research of Central Colleges (Grant No. CHD300102269305, CHD300102268305, Chang'an University). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**System**} & \multicolumn{3}{c}{**Mate40 (m)**} & \multicolumn{3}{c}{**P40 (m)**} & \multicolumn{3}{c}{**DH04 (m)**} \\ \cline{2-10}  & **East** & **North** & **Up** & **East** & **North** & **Up** & **East** & **North** & **Up** \\ \hline G & 6.89 & 7.36 & 8.51 & 5.54 & 5.94 & 9.00 & 0.63 & 0.57 & 0.72 \\ C & 4.22 & 3.34 & 9.96 & 4.57 & 3.73 & 8.89 & 0.67 & 0.86 & 1.47 \\ GC & 3.47 & 4.30 & 8.57 & 4.20 & 3.49 & 8.07 & 0.58 & 0.40 & 0.89 \\ GCE & 3.45 & 4.41 & 8.60 & 3.88 & 3.39 & 7.83 & 0.47 & 0.53 & 0.84 \\ G (L1/L5) & 6.85 & 7.30 & 8.15 & 5.30 & 5.82 & 8.80 & 0.06 & 0.11 & 0.16 \\ \hline \hline \end{tabular}
\end{table}