Page 144 - 卫星导航2021年第1-2合期

Liu et al. Satell Navig (2021) 2:6 Page 11 of 17

Fig. 9 Single-epoch ambiguity resolution success rates based on
single-frequency observations

Fig. 11 The positioning errors with dual-frequency BDS-2/BDS-3
observations at the elevation cut-of angle of 10°

E/N/U) was better than that for BDS-2 only solution
(0.41 cm/0.44 cm/1.74 cm), showing good agreement
with the previous PDOP results. If BDS-3 and BDS-2
are tightly combined, the positioning accuracy can
then be signifcantly improved, i.e., the RMS values of
Fig. 10 Single-epoch ambiguity resolution success rates based on
dual-frequency observations 0.24 cm/0.27 cm/1.18 cm in the E/N/U. Te 3D position
RMS was 1.84 cm for BDS-2, 1.43 cm for BDS-3, and
1.23 cm for tightly combined BDS-3/BDS-2. Te posi-
Figure 10 shows the ambiguity resolution success rates tioning accuracy for the BDS-3 B1C/B2a solution was
based on dual-frequency observations at diferent eleva- slightly lower than the BDS-3 B1I/B3I solution. Tis is
tion cut-of angles. It was observed that if the elevation reasonable considering its higher PDOP values due to the
cut-of angle was below 25°, almost 100% success rates absence of C59 and C60.
were obtained for all the solutions. With increasing ele-
vation cut-of angle from 25° to 40°, the success rates of Kinematic test
BDS-2 and BDS-3 B1I/B3I solutions decreased slightly A kinematic test was performed on June 24, 2020 from
to approximately 94.2% and 91.9%, whereas those of the 06:45 to 08:00 GPS Time (GPST) in Wuhan, China. In the
BDS-3 B1C/B2a solutions decreased dramatically to experiment, two Trimble Alloy receivers were used as the
approximately 58.3%. For the tightly combined BDS-3/ base and rover. Te base receiver and antenna (Trimble
BDS-2 solutions, 100% success rates were achieved Zephyr Geodetic 2) were located beside the Liangzi Lake
under all elevation cut-of angles. Hence, we conclude Avenue, with an open-sky view. Te rover receiver and
that tightly combined BDS-3/BDS-2 could signifcantly antenna (Trimble Zephyr Model 2) were installed on top
improve ambiguity resolution performance compared of a car driving along the Liangzi Lake Avenue, with an
with BDS-2 or BDS-3 alone, particularly under challeng- approximate speed of 50 km/h. Distance between rover
ing or severe observational conditions. and the base was approximately 0.3–7.9 km during the
Figure 11 shows positioning errors in the E, N, and U
components for BDS-2, BDS-3, and tightly combined
BDS-3/BDS-2 using dual-frequency observations at the
elevation cut-of angle of 10°. Te corresponding posi- Table 6 RMS of the single-epoch BDS-2/BDS-3 RTK
tioning accuracy (only for ambiguity fxed solutions) positioning errors
is listed in Table 6. As shown, the positioning errors Observations E (cm) N (cm) U (cm) 3D (cm)
were primarily within the range of − 1.0 to 1.0 cm in
the East and North components and the range of − 4.0 BDS-2 B1I/B3I 0.41 0.44 1.74 1.84
to 4.0 cm in the Up component. About the B1I/B3I sig- BDS-3 B1I/B3I 0.31 0.34 1.35 1.43
nals, the positioning accuracy for BDS-3 only solu- BDS-3 B1C/B2a 0.52 0.62 1.36 1.58
tion (RMS values of 0.31 cm/0.34 cm/1.35 cm in the BDS-2/BDS-3 B1I/B3I 0.24 0.27 1.18 1.23