# Precise Positioning of BDS, BDS/GPS: Implications for Tsunami Early Warning in South China Sea
## 5 Conclusions  
In this study, we investigated the precise positioning performance of BDS and BDS/GPS in the Asia-Pacific region, and we specifically focused on their applications to tsunami early warnings  
Figure 7: Simulated tsunami scenarios. The color map shows the maximum wave height in the forward model (Figure 6a) after 6 h of tsunami propagation. Vertical bars are maximum wave heights as recorded at selected coastal locations for the three propagation models: the forward model (black); the model with the source as inverted from BDS-displacements (dark grey, Figure 6b); and the model with the source as inverted from joint BDS/GPS-displacements (light grey, Figure 6c).  
in the SCS region. By analyzing two MGEX stationary stations, we demonstrated that BDS and GPS display similar positioning accuracy in the Asia-Pacific region. Combined BDS/GPS solution not only shows a somewhat higher degree of precision but, what is even more important for operational implementation in decision-making applications like tsunami early warnings, also improves the robustness.  
By considering a scenario of a devastating tsunami in the Southern China Sea triggered by a Mw = 8.0 earthquake along the Manila trench, we propose deploying a continuous BDS/GPS-network at the western coast of the Luzon Island, Philippines. This network, if complemented with the modern real-time processing technique (here TPP), will contribute to a very fast (2-3 min) earthquake evaluation and source inversion, moving toward a higher reliability of the local and regional tsunami early warning.  
Using a scenario with a smaller but still tsunamigenic earthquake (Mw = 7.5), we demonstrate that the advantage of combined BDS/GPS over single GNSS processing by source inversion grows with decreasing earthquake magnitudes. To conclude, BDS and BDS/GPS can become an important component of the future TEWS in the SCS, although numerous factors need to be optimized in future studies.  
Considering that the BDS constellation is still under construction, with increasing numbers of BDS satellites and ground-tracking stations arising in the coming years, its visibility in other places in the world will improve significantly, and the orbit and clock bias products will be more accurate, which indicate that precision of BDS is expected to be equal on a global level. That is to say, the concept of BDS and BDS/GPS as a tsunami early warning component is not limited to the Asia-Pacific region, but will be able to be applied worldwide.  
[PERSON] is supported by the China Scholarship Council (CSC) for his PhD study in the German Research Centre for Geoscience. [PERSON] is supported by the Helmholtz Association through the GeoSim program. This study was also supported by the National Natural Science Foundation of China (Grant No. 41504010; 41574027; 41325015; 41231174). We appreciate valuable comments from the three reviewers which improve this manuscript greatly.  
[PERSON] initialized the idea and conception; [PERSON], [PERSON] and [PERSON] wrote the manuscript; All authors reviewed the manuscript.  
The authors declare no conflict of interest.