## 4 Results and Discussion
### Performance of Ranging and Positioning  
The signal collected in Sanya, China was processed off-line used GNSS Receiver to analyze the ranging difference. This signal yielded the most consistent results as to all five satellites are visible for a significant time. Respectively, Figures 12 and 13 depict the ranging difference from 0.05 chips correlator spacing of L1 CP transmitted by QZS-1 and Vespucci for several correlator spacing. The ranging difference is averaged by 2000 pseudorange samples. As expected, the ranging difference of L1 CD using BOC(1,1) are similar for different correlator spacing and increases with correlator spacing. Nevertheless, the ranging difference of TMBOC(6,1,4/33) vary significantly with different correlator spacing. The worst ranging difference of L1 CP using TMBOC(6,1,4/33) is 0.25 chips correlator spacing in various correlator spacing, followed by 0.2 chips and 0.3 chips. As shown in Figures 14 and 15, the ranging fluctuations of the difference of L1 CP and L1 CD transmitted by each satellite are calculated by (7). For Vespucci (green line), regardless of whether Gaussian noise is removed or not, the ranging difference of L1 CP using 0.2 chips, 0.25 chips and 0.3 chips is worse than L1 CD, but it is superior to L1 CD using the other correlator spacing. This phenomenon is repeated in the other three QZSS satellites. But there is a downward trend from 0.125 chips to 0.15 chips, which indicates that multipath and interference affect the signal at 0.125 chips. By comparing the ranging difference, it is proved that the resistance to complex environments of TMBOC(6,1,4/33) outperforms that of BOC(1,1). Figure 12: Ranging difference from reference 0.05 chips spacing for QZS-1 L1 CP (BOC). Figure 13: Ranging difference from reference 0.05 chips spacing for Vespucci L1 CP (TMBOC). As shown in Figure 14, for QZS-1 (blue line), although both L1 CD and L1 CP use BOC (1,1) modulation, L1 CP ranging is more accurate due to higher C/N0. However, after removing Gaussian noise in Figure 15, this phenomenon becomes less obvious. Referring to Table 1, it is worth noting that satellites with higher C/N0 produce a little difference in ranging for both BOC(1,1) and TMBOC(6,1,4/33). But after smoothing in Figure 15, the ranging difference of each satellite has been independent of the C/N0. Since the constellation of GPS III is under development, the L1C signal transmitted by GPS III is merely available in the segment of the period. As a consequence of using joint positioning, the complementary effects between the constellations will be demonstrated using the signal collected in Xi'an. In order to illustrate the influence of the geometry of the satellite constellation, the positioning results of Xi'an are shown in the topocentric coordinate system. Succeedingly, the advantages of joint positioning using the L1C signal will be demonstrated using the signal collected in Sanya. In order to make a fair comparison, the same segment of the period is used in each comparison to ensure that the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Component of L1C** & **QZS-1** & **QZS-2** & **QZS-3** & **QZS-4** & **Vespucci** \\ \hline L1 CD & 44.9 & 43.4 & 41.4 & 45.2 & 40.3 \\ L1 CP & 49.9 & 48.8 & 46.5 & 50.8 & 45.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Average C/N0 of each satellite in 1 min (dB-Hz). Figure 14: Ranging difference of L1 CD (solid line) and L1 CP (dashed line) transmitted in each satellite with different correlator spacing without smoothing. Figure 15: Ranging difference of L1 CD (solid line) and L1 CP (dashed line) transmitted in each satellite with different correlator spacing after smoothing. positioning results are in the same constellation geometry. However, the positioning error of Sanya is expressed in the WGS-84 coordinate system for the purpose of clearly comparing the error. Table 2 lists two periods of QZSS and GPS III satellites visible in Xi'an.