## 5 Discussion and Conclusions  
We have presented static and kinematic PPP results in the modes of BeiDou-only, GPS-only and BeiDou/GPS systems, respectively. The visibility of the current BeiDou satellite constellation, multipath combinations and undifferenced phase and code observation residuals of BeiDou satellites are used in the analysis. The results are compared with the \"ground truth of stations\". The following conclusions can be drawn:  
1. The analysis of multipath combinations shows that the MPCs of BeiDou code measurements are higher than those of GPS code measurements at the testing stations;
2. The daily static PPP solutions using BeiDou code and phase measurements demonstrate that the horizontal precision is better than 1.0 cm while the vertical precision is better than 3.0 cm in the Asian-Pacific region. For the region having less observed BeiDou satellites,  
Figure 13: RMS values of the undifferenced LC and PC residuals for GPS satellites of all individual sites.  
\begin{table}
\begin{tabular}{c c c} \hline
**PRN** & **LC(cm)** & **PC(m)** \\ \hline C01 & 0.71 & 1.29 \\ C03 & 0.67 & 1.35 \\ C04 & 0.89 & 2.02 \\ C05 & 0.85 & 1.92 \\ C06 & 0.84 & 1.33 \\ C07 & 1.12 & 1.37 \\ C08 & 0.85 & 1.24 \\ C09 & 0.86 & 1.16 \\ C10 & 0.89 & 1.25 \\ C11 & 1.12 & 1.25 \\ C12 & 1.62 & 1.42 \\ Mean & 0.95 & 1.42 \\ \hline \end{tabular}
\end{table}
Table 3: Average values of the RMS of undifferenced LC and PC residuals for all BeiDou satellites.  
the horizontal precision of BeiDou-only PPP solutions reaches 3.0 cm. The horizontal precision of BeiDou-only kinematic PPP solutions is better than 3.0 cm and the vertical precision is better than 6.0 cm, which is close to that of GPS-only kinematic PPP. The convergence time of BeiDou-only kinematic PPP is longer than that of GPS-only kinematic PPP;
3. The daily static PPP solutions using BeiDou/GPS code and phase measurements demonstrate that the horizontal and vertical precisions are better than 1.0 cm, which is close to those of GPS-only static PPP. The horizontal precision of kinematic BeiDou/GPS PPP solutions is better than 2.0 cm while the vertical precision is better than 5.0 cm. The results improve significantly compared to that of BeiDou-only and GPS-only kinematic PPP. The convergence time of BeiDou/GPS kinematic PPP is also shorter than that of BeiDou-only and GPS-only kinematic PPP. The East and North components converge faster than the Up component. And less than 1 hour is used in all the components;
4. The analysis on the residuals shows that BeiDou undifferenced LC and PC residuals vary with orbital characteristics. The BeiDou code and phase residuals are higher than the GPS ones, which may be due to the multipath error.  
Finally, it should be pointed out that the performance evaluation of BeiDou PPP is for preliminary results since the BeiDou constellation is not yet completed. Furthermore, as the number and proper distribution of the ground tracking stations increase, the accuracy of satellite orbit and clock biases will also improve greatly [31]. The precision of BeiDou positioning may be significantly improved in the future. Moreover, the determination and optimization of the phase center corrections in the satellites and receiver terminals may also benefit the performance of BeiDou positioning.  
This work was supported by the GNSS Research Center at Wuhan University and the National Natural Science foundation of China (No. 41204029; No. 41231174), the Outstanding Youth Paper foundation of CSNC (CSNC2012-QY-1) and the \"111 Project\" of China (No. B07037). The authors are thankful to [PERSON], who considerably revised the paper. In addition all the reviewers are appreciated for their comments and suggestions, which significantly improved our manuscript.