Long-Term Performance Evaluation of BeiDou PPP-B2b Products and Its Application in Time Service

Round 1

Reviewer 1 Report

The BDS-3 PPP-B2b signal can provide real-time PPP service, which is a hot topic recently. This paper focus on evaluation of the long-term performance of PPP-B2b and its application in time service. They evaluated 557-day PPP-B2b products. Overall, the data in this paper is large and the experimental results are reliable. Thus, the paper can be accepted for publication after minor revision.

1) Why do you only give one-week results in PPP one-wat timing experiment? Please add more explanation.

2) As for SISRE STD, GPS is larger than that of BDS-3 while the orbit accuracy is at the same level, please check and confirm these results.

3) The caption of Figure 5 and 6, “Time series of PPP-B2b products” and corresponding description should be modified.

4) p does not have to be bold in Table 2

Author Response

Q1) Why do you only give one-week results in PPP one-wat timing experiment? Please add more explanation.

A1) Thanks for your comment. According to the results, only station lck4 in this week show a high-performance clock series. Thus, limited to the data used in this paper, only one-week results of station lck4 is given in PPP one-way timing. We have now added more explanation.

Q2) As for SISRE STD, GPS is larger than that of BDS-3 while the orbit accuracy is at the same level, please check and confirm these results.

A2) Thanks and we have checked these results again. We find that we used BDS satellite PCO from IGS and it is not compatible with PPP-B2b products. We have replaced the satellite PCO from BDS official website and updated the results.

Q3) The caption of Figure 5 and 6, “Time series of PPP-B2b products” and corresponding description should be modified.

A3) Thanks and we have modified them.

Q4) p does not have to be bold in Table 2

A4) Thanks for your comment and we have corrected it.

Reviewer 2 Report

The unique contribution of paper is the long-term evaluaion of preceise timing syncronization using statellite based open PPP service. This paper is well-described the methods and the results with some minor improvements as shown bellow:

Abstract:  The authors describe that BDS-3 satellite clock is greatly better than GPS satellite clock, and SISREs are 0.13ns and 0.22ns for GPS and BDS-3. It is inconsistent with the description in pp.9, they should be 0.22ns and 0.13ns.

Table 2.: The authors should describe whether the weighting is applied for code (phase) only or phase/code.

Author Response

Q1) Abstract:  The authors describe that BDS-3 satellite clock is greatly better than GPS satellite clock, and SISREs are 0.13ns and 0.22ns for GPS and BDS-3. It is inconsistent with the description in pp.9, they should be 0.22ns and 0.13ns.

A1) Thanks for your comment and we have modified this typo.

Q2) Table 2.: The authors should describe whether the weighting is applied for code (phase) only or phase/code.

A2) Thanks for your comment and we have added description.

Reviewer 3 Report

The manuscript deals about the application of BDS-3 PPP-B2b products for precise timing applications. It is reasonably well written and I have only few comments:

- In Introduction nonnegligible constant satellite-specific biases in PPP-B2b clock offsets are mentioned. What is the cause of these biases?

- Eq. 2: please explain the symbols v_R, v_C, v_A.

- Typo in Eqs. 7, 9, 10: n should be m.

- Eq. 11: there are no error terms here.

- Eq. 12: please explain the symbol U_2m and why 10^-4?

- Sect. 3: the BDS-3 satellites show a linear trend in the timeseries, but there is no explanation for this.

Author Response

Q1) In Introduction nonnegligible constant satellite-specific biases in PPP-B2b clock offsets are mentioned. What is the cause of these biases?

A1) Thanks for you comment. We have added some discussion in the introduction to explain the cause of these biases.

Q2) Eq. 2: please explain the symbols v_R, v_C, v_A.

A2) We have added explanation in the revised paper.

Q3) Typo in Eqs. 7, 9, 10: n should be m.

A3) Thanks for your comment and we have revised them.

Q4) Eq. 11: there are no error terms here.

A4) Thanks for your comment and we have omitted them for simplicity. We have now added corresponding descriptions.

“For simplicity, the noise terms are omitted and the IF GNSS observations can be described as:”

Q5) Eq. 12: please explain the symbol U_2m and why 10^-4?

A5) Thanks and we have added corresponding descriptions.

Q6) Sect. 3: the BDS-3 satellites show a linear trend in the timeseries, but there is no explanation for this.

A6) Thanks and we have added explanations in the revised paper.

Before Fig.1: “It should be noted the linear trends in single-differenced satellite clock are caused the different processing strategies and will be absorbed into receiver clock. It can be canceled by single-difference between two receivers and will not affect the accuracy of positioning and time synchronization. ”