Performance Assessment of Multi-GNSS Real-Time Products from Various Analysis Centers

Round 1

Reviewer 1 Report

The performance of real-time PPP relies primarily on the availability and quality of orbit and clock corrections. This manuscript presents a comprehensive evaluation of multi-GNSS real-time products of IGS RTS, from the aspects of the latency, availability and accuracy. This could be provided as a reference for the selection of real-time products when perform RTPPP.

The manuscript is well written and suitable for our journal. It can be accepted after minor modification. I have read the manuscript in detail. Below, I provide some specific comments.

1. The last sentence of the abstract, “… with the GREC combination had positioning errors better than 5.2 cm.” should be “… with the GREC combination had positioning errors smaller than 5.2 cm.”

2. The sentence above the section 2 methods, “Section 5 reports on the precision point positioning experiment that aimed” should be “Section 5 reports on the precise point positioning experiment that aimed”

3. The y-axis value of figure 1 should be multiplied by 100, they are percentages.

4. The equations(5) should be corrected, the first sub-equation doesn’t conform to the matrix algorithm, the term before the multiplication sign should be a row vector, while the term after the multiplication should a column vector.

5. In Figure 6, for the IGSO products of GFZ, accuracy of cross-track component is better than that of radial and along-track, it is unusual, check it carefully.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

You have presented lots of results. But you could pay more attention to the relationships between the accuracy, latency, availability, satellite number of the products and the final positioning performance. 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

This paper comprehensively analyzes almost all IGS real-time products in the term of availability, delay, product accuracy and application, intuitively shows the real-time product status of different analysis centers and satellite constellations, and the conclusions prompt the application of real-time service. This work is worth to publish in the journal as long as the following comments can be answered properly.

1. Abstract, the authors should point out that the values of “10.8 cm and 9.5 cm” is for GPS-only PPP.

2. The motivation of this research is not strong enough. I suggest the authors to add more description on it.

3. How to understand the STD of latency is assessed as a factor?

4. What is the definition of data availability in this research?

5. In Figure 1, the tick label in Y-axis should be 80, 90, 100, or just remove the “%” in the label of Y-axis.

6. Section 3. “affected to the network environment of receiving” should be “affected by”

7. Does the consistency between real-time products of WHU and reference products affect the results of accuracy evaluation? I suggest that the authors to choose an unrelated multi-GNSS final precise products, such as CODE.

8. Section 5.2. “a median of convergence time” should be “the median of convergence time”

9. Section 5.2. “pay more attention to the satellite models”. What do you mean by “satellite model”?

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Much better than the previous version.