## 5 Experiment  
To verify the improvement effect in the SFSE baseline resolution of GPS and BDS augmented by QZSS, two groups of experiments were conducted with a 12.5 km baseline of the HKQT-HKLM stations and a 4.8 km baseline of the HKMW-HKPC stations, respectively. Their distributions and positions in Hong Kong are marked in Figure 5. To make the two groups with different common satellites, the date from different time periods were used. The time periods of 12.5 km and 4.8 km baseline data ranged from 12:00 to 24:00 on 9 February 2018 and from 8:00 to 20:00 on 28 February 2018, respectively. The sampling frequency is 5 s and the mask angle is set to 5\({}^{\circ}\). The frequencies adopted here are GPS L1, QZSS L1 and BDS B1. The receiver types of the longer baseline are both Trimble NetR9 and those of the shorter baseline are both Leica GR50. Therefore, the ISBs between GPS L1 and QZSS L1 can be ignored here. Stations HKQT and HKLM can track 3 QZS, while stations HKPC and HKMW can only receive carrier signals from J01 and J02 (QZS numbered 01 and 02).  
To clearly present the improvement of the GPS and BDS SFSE baseline resolution when augmented by QZSS, we added QZS to DD processing one-by-one immediately following their number (J01, then J02 and finally J03). Since LCM was used in BDS/QZSS, the number of QZS in integrated BDS/QZSS is at least 2. Therefore, we used 8 kinds of processing strategies for the HKQT-HKLM baseline (case 1) as follows: GPS, GPS + 1 QZS, GPS + 2 QZS, GPS + 3 QZS, BDS, BDS + 2 QZS, BDS + 3 QZS and BDS + GPS + 3 QZS. Six kinds of combination forms were used in the HKMW-HKPC baseline including GPS, GPS + 1 QZS, GPS + 2 QZS, BDS, BDS + 2 QZS and BDS + GPS + 2 QZS and were analyzed in case 2, where, the combination of BDS/GPS/QZSS was only used in contrast.  
Six indicators are used to evaluate the experimental results, NOS, PDOP, ADOP, Brst, Arst, and the baseline precision. The baseline precision is calculated through two steps. First, the mean result of the  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Mask Angle/\({}^{\circ}\)** & **0** & **5** & **10** & **15** & **20** & **25** & **30** & **35** \\ \hline \multirow{4}{*}{ADOP} & GPS & 0.3424 & 0.3423 & 0.372 & 0.522 & 0.7501 & / & / & / \\  & GPS/QZSS & 0.2327 & 0.2307 & 0.2391 & 0.2788 & 0.3378 & 0.4459 & 0.6696 & / \\  & BDS & 0.2006 & 0.2004 & 0.2028 & 0.2086 & 0.2156 & 0.266 & 0.2808 & 0.4104 \\  & BDS/QZSS & 0.1811 & 0.181 & 0.1822 & 0.1882 & 0.1964 & 0.2405 & 0.2574 & 0.3741 \\ \hline \multirow{4}{*}{Bsrt/\%} & GPS & 95.58 & 95.62 & 91.94 & 83.38 & 72.36 & / & / & / \\  & GPS/QZSS & 99.02 & 99.6 & 99.06 & 96.12 & 90.41 & 80.59 & 67.35 & / \\  & BDS & 99.79 & 99.79 & 99.71 & 99.52 & 99.37 & 96.93 & 96.16 & 84.7 \\  & BDS/QZSS & 99.93 & 99.94 & 99.91 & 99.8 & 99.63 & 97.66 & 96.87 & 86.76 \\ \hline \hline \end{tabular}
\end{table}
Table 3: ADOP and bootstrapped success rate of different systems with different mask angles.  
same data calculated by RTKLIB was used as a reference, which should be correct and reliable since the combination of GPS/BDS/QZSS and frequencies L1/L2 are used. Then the RMS errors of the E, N and U components are computed by  
\[X_{RMSE}=\sqrt{\frac{\sum\left(X_{i}-X_{r}\right)^{2}}{n}} \tag{15}\]  
where \(X_{i}\) denotes the E/N/U sequences of the baseline resolution and \(X_{r}\) donates the reference value; \(X_{RMSE}\) represents the RMS errors of the E/N/U component and n is the length of the sequence. Then the precision of the baseline can be computed by  
\[precision=\sqrt{E_{RMSE}{}^{2}+N_{RMSE}{}^{2}+U_{RMSE}{}^{2}} \tag{16}\]