# The Effect of BDS-3 Time Group Delay and Differential Code Bias Corrections on Positioning
## 5 Conclusions  
In this present work, we first summarize currently available BDS-3 TGD and DCB parameters, and the relationship between TGD and DCB was revealed with numerical experiments. Comparisons showed that the value of broadcast TGD in the broadcast ephemerides agreed well with the CAS DCB. Then, correction models for various occasions of BDS-3 positioning were developed. The impact of TGD or DCB parameters on BDS-3 single-frequencies and dual-frequency combinations of SPP and PPP positioning were evaluated by three different scenarios schemes (\"dcb-corr\", \"tgd-corr\" and \"non-corr\"). With analysis of the effects of TGD and DCB on BDS-3 positioning, we found that the uncorrected TGD or DCB parameters seriously affected the positioning accuracy of the SPP, whether using single- or dual-frequency combinations. The TGD broadcasted in the broadcast ephemeris and the DCB parameters provided by CAS are both beneficial to the performance of BDS-3 positioning. Although the effects of differential code biases can be mitigated as time goes by, and similar positioning accuracy can be obtained after convergence, the bias can be absorbed and affected by other parameters. Consequently, convergence time and receiver clock will be absorbed by the bias. Thence, for the high-performance positioning and timing users, the TGD and DCB correction models must be considered seriously.  
Furthermore, for multi-GNSS and multi-frequency, observations from different constellations, signals, frequencies and channels need to be processed along with each other; therefore, it is very important to consider the differential code biases in a consistent modeling of all observations. We need to consider the impact of differential code bias particularly in the applications of multi-GNSS positioning, precise timing and tropospheric delay estimation. We will do research on this in the future.  
[PERSON], [PERSON], [PERSON] and [PERSON] conceived and designed the experiments; [PERSON] performed the data analysis and wrote the article; [PERSON], [PERSON] and [PERSON] validated the experimental results and reviewed the paper. [PERSON] and [PERSON] supervised the experiments. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Beidou New Time-space Intelligent Industry Development Collaborative Innovation Center (No. 0508-2).  
Figure 25: Time series of BDS-3 PPP receiver clock obtained with different schemes at BCH and HMNS stations.  
**Institutional Review Board Statement:** Not Applicable.  
**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.  
**Data Availability Statement:** No new data were created or analyzed in this study. Data sharing is not applicable to this article.  
**Acknowledgments:** The contribution of data from iGMAS is gratefully acknowledged. The authors gratefully acknowledge Wuhan University for providing products, and the Chinese Academy of Sciences for providing DCB products.  
**Conflicts of Interest:** The authors declare no conflict of interest.