## 3 Characteristics of Xiaomi Mi 8 Raw GNSS Observations
### Pseudorange Observations
The pseudorange outlier percentage for the dynamic test is calculated with the data of track 1.  
the code rate is 10 times higher than that of the coarse/acquisition (C/A) code, then theoretically, the accuracy of L5/E5 pseudorange should be better than L1/E1. Moreover, a higher code rate gives a better defined peak of a spreading code correlation vector. In other words, the L5/E5 is superior, especially in cities, because it is less prone to distortions from multipath reflections than L1/E1 [18]. The use of L5/E5 should be important for improving the positioning performance of Xiaomi Mi 8 in urban environments. Thirdly, it is obvious that the pseudorange SD residuals for Xiaomi Mi 8 decrease with the increase of C/N0 for both L1/E1 and L5/E5 measurements. In addition, SD residuals of GPS/Galileo/QZSS are much smaller than that of BeiDou/GLONASS; especially for GLONASS, the RMS of the SD pseudorange residuals reaches 9 m. However, the relationship between the pseudorange SD residuals and the elevation (Figure 10) is not as evident as that in Figure 9; the pseudorange SD residuals nearly remain the same at different elevations. Therefore, a C/N0-dependent weighting strategy, instead of the elevation-dependent weighting model, is used in the following GNSS positioning experiments. Figure 10: RMS statistics of the GPS/Galileo/QZSS/BeiDou/GLONASS L1/E1 (**a**) and L5/E5 (**b**) SD pseudorange residuals against the elevation for dynamic data (track 1). Figure 9: Root mean square (RMS) statistics of the GPS/Galileo/QZSS/BeiDou/GLONASS L1/E1 (**a**) and L5/E5 (**b**) SD pseudorange residuals against the C/N0 for dynamic data (track 1). Figure 11 shows the differences between the raw pseudorange measurements and the ionosphere-free combination pseudorange measurements for Septentrio receiver and Xiaomi Mi 8 about satellites G08/E27/J03, respectively. These differences mainly include the ionospheric delay, broadcast group delay of pseudorange P\({}_{i}\) (\(i\) = 1, 5), and the synthetic pseudorange noise for P\({}_{i}\) and P\({}_{IF}\). Clearly, for the Septentrio receiver, the differences are relatively stable within a small range, which indicates that the pseudorange noise is much smaller than the ionospheric delay, and the ionosphere-free combination pseudorange measurements can be useful for the Septentrio receiver; the influence of the ionospheric delay and broadcast group delay was at meter-level when the data were collected. For the Xiaomi Mi 8, the differences vary from about \(-\)30 to 30 m. Clearly, the noise of the ionosphere-free combination pseudorange measurements is much larger than the influence of ionospheric delay and broadcast group delay. When processing the raw dual-frequency pseudorange measurements from Xiaomi Mi 8, the single-frequency mode is more suitable. Figure 11: Differences of raw pseudorange measurements and the ionosphere-free combination pseudorange measurements for Septentrio receivers about satellites (**a**) G08, (**c**) E27, (**e**) J03 and Xiaomi Mi 8 about satellite (**b**) G08, (**d**) E27, (**f**) J03, respectively. P\({}_{i}\) (\(i\) = 1, 5) are L1/E1 and L5/E5 pseudorange measurements, respectively. P\({}_{IF}\) means ionosphere-free combination pseudorange measurements.