Page 128 - 卫星导航2021年第1-2合期

Xia et al. Satell Navig (2021) 2:8 Page 14 of 19

Fig. 16 Cumulative probability of smartphone horizontal position
deviation based on diferent satellite systems

Fig. 14 Numbers of visible satellites and GDOP values of four Table 3 2D positioning deviations of Huawei Mate 20
systems in the static test based on diferent satellite systems
Probability 2D positioning deviations based on diferent
satellite systems (m)
BDS GPS Galileo GLONASS BDS/
GPS/
Galileo

68% 1.43 1.81 0.67 8.10 0.90
95% 2.88 3.44 2.17 15.23 1.56

Figure 17 displays the positioning deviations in the
three directions in the time domain based on diferent
systems.
Before the 2000th second, Galileo positioning devia-
tions in the east and up directions are relatively large,
only smaller than GLONASS. Compared with Fig. 14, we
can fnd that this is due to the very large GDOP values
of Galileo during this period. Similarly, the poor satellite
geometry between the 6745th second and the 6935th sec-
ond leads to relatively large deviations in BDS position-
ing results in the north direction. From Fig. 17, one can
see the positioning results of the BDS/GPS/Galileo fusion
Fig. 15 Static smartphone positioning results based on diferent are concentrated and stable in the three directions, which
satellite systems and their combination
indicates the multiple systems can improve positioning
performance. Regarding the single-system positioning,
the single-system positioning. On the other hand, the BDS shows the satisfactory performance of smartphone
high pseudorange precision of Galileo support the good positioning in all three directions, as well as GPS. Te
smartphone SPP performance. For BDS, its horizontal positioning deviation of Galileo after the 2000th second
R95 value reaches 2.88 m, which is greater than Galileo, is small, comparable to the BDS/GPS/Galileo.
but less than GPS and GLONASS. And a similar situa- Since the positioning deviation is a time series with zero
tion occurs for the R68 (2D), which is 1.43 m for BDS. mean, we can calculate the standard deviation to measure
Notably, the R68 value of Galileo is only 0.67 m, smaller the positioning precision. Te results are listed in Table 4.
than that of BDS/GPS/Galileo, which is 0.90 m. Despite Te maximum deviation is also given to assess the sta-
this, the deviations of Galileo are in the range of 0.67 m bility of the positioning results. As can be seen, the hori-
to 2.17 m, which still account for a considerable pro- zontal positioning precision of BDS is superior to GPS
portion, lowing its overall horizontal precision. and GLONASS, and its vertical precision is better than