## 5 Conclusions  
The effectiveness of the combined attitude model and receiver PCVs model were investigated in depth. Two strategies about attitude modes and PCV modeling are introduced into Jason-3 POD to integratedly compare their performance. Some conclusions have been drawn:  
1. A combined attitude model based on experimental analysis was designed as the alternative or revision of event file for Jason-3 POD. To validate the feasibility of the combined attitude mode, we analyzed the effects of different attitude modes on PCO estimation, PCO correction and POD. The differences in PCO correction provided a method to define the transition threshold of combined attitude and a validation way for attitude modes. The PCO estimation with combined model are better than those with nominal attitude and slightly worse than those with quaternions. The POD results showed that the orbital accuracy with the combined attitude is slightly more stable than that of event file.
2. The receiver PCO was estimated in-orbit and the PCVs are modeled by residual approach for Jason-3 satellite. By introducing receiver PCVs map, the orbital accuracy can be improved by millimeter level, in which the mean residuals RMS reduced by 1.9 mm, the 3D-RMS position difference is improved by 5.7 mm, and accuracy of equivalent distance error by SLR validation is improved by 4.1 mm.
3. The eight schemes were designed to integratedly verify the feasibility of the combined attitude mode and receiver PCVs. The orbital accuracy with receiver PCVs map using nominal attitude, event file, the combined attitude, and quaternions are approximately 197.98 cm, 7.28 cm, 5.70 cm, and 2.97 cm, respectively. The accuracy using the combined attitude is higher than that of event file, which also prove the feasibility of the combined attitude in integrated POD. The integrated effects of attitude modes and receiver PCVs for POD accuracy and stability are almost consistent with the effect of a single variable.  
The combined attitude mode provides a revision of event file in the absence of quaternions or inconvenient to use, even in the near-real-time OD. The orbital accuracy can be further improved by integratedly introducing receiver PCVs with all mentioned attitude modes. The optimal POD results indicate that the orbital mean radial RMS are close to 1 cm and the 3D-RMS position difference are within 3 cm, which satisfy the needs of scientific missions for Jason-3 satellite.  
In this work, [PERSON] proposed the idea; [PERSON] and [PERSON] designed and analyzed the experiment results; [PERSON] and [PERSON] collected the experimental data and wrote the paper. [PERSON], [PERSON] and [PERSON] supervised its analysis and edited the manuscript. All authors reviewed the manuscript.  
This work was supported by the Collaborative Precision Positioning Project funded by the Ministry of Science and Technology of China (No. 2016 YFB0501900) and China Natural Science Funds (No. 41674022, 41674020, 41574015).  
The authors acknowledge LU JIAXI International team program supported by the K.C. Wong Education Foundation and CAS. The authors are grateful to CODE and CNES for providing the precise products and Jason-3 orbits, respectively. Meanwhile, we would like to thank the anonymous reviewers for their valuable comments.  
The authors declare no conflict of interest.