Multimodal Distribution of Positioning Errors in NRTK GNSS CORSs: A Case Study in Sicily (Italy)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General Comments:

This paper takes Sicily, Italy as an example to conduct a detailed evaluation of the application performance of the CORS network. The paper has done a lot of meticulous work, but there are a large number of language, text and formatting errors, and the presentation form of the paper needs to be further improved.

Detailed comments:

1. On line 56, please verify whether "quadri - co n stellation" has spelling mistakes.
2. On line 62, "GNNS applications" has a spelling error. Please check if there are the same mistakes in other parts of the text.
3. On line 68, why are the full names of abbreviations such as VRS and FKP in italic?
4. On line 77, there is a formatting issue with "in th e s e works adopting a n NRTK VRS approach in Australia". There are many similar formatting problems in the text, please correct them.
5. The "Introduction" needs further improvement. Currently, this section uses too many paragraphs for description, and it is difficult for readers to clarify the logical relationship between them. It is recommended to reorganize this part of the content.
6. On line 177, what does "CGPS" mean?
7. On line 345, "VTR" is not explained.
8. In Section 3.1, many short paragraphs are used for description. It is recommended to reorganize it.
9. The title of Figure 3 should be placed below the figure.
10. On line 494, "Tables 1-2" suddenly appears. What does it mean?
11. It is recommended to replace all the tables in the text with the form of three-line tables.
12. The conclusion part has too much content. It is recommended to streamline it.

Author Response

Please see the attachment.

Best regards

Gino Dardanelli

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. There are a large number of undefined abbreviations in the text, such as "iMAX". The author should thoroughly investigate such issues.

2. This article contains a large number of abbreviations, some of which are even rather rare. It is strongly recommended that the author add a section at the end of the paper to centrally define all abbreviations.

3. Table 2 shows that tests such as Shapiro-Wilk and Anderson-Darling were used, but the sample size of some correction streams (such as iMAX) was small (~50 measurements), and such tests are prone to false negative results in small samples [1].

[1] Razali, Nornadiah Mohd, and Yap Bee Wah. "Power comparisons of shapiro-wilk, kolmogorov-smirnov, lilliefors and anderson-darling tests." Journal of statistical modeling and analytics 2.1 (2011): 21-33.

4. There are some puzzling points in the description of the k-means classification in line 538. First of all, what is the basis for dividing it into two categories a priori? Secondly, more parameters of the k-means algorithm should be clearly defined in the text, such as the iteration termination conditions (such as the maximum number of iterations, convergence threshold) and the selection methods of the initial clustering centers (such as random initialization or K-means ++), etc.

5. In Table 7, the ANOVA algorithm is used for test, but the degrees of freedom (df_b, df_w) corresponding to the F value are not marked. The degree of freedom is the decisive parameter of the F-distribution pattern. The absence of degrees of freedom will cause the significance judgment of the F-value to lose the benchmark. The author should consider adding necessary parameter descriptions to all the test algorithms to ensure the feasibility of the algorithms.

6. In line 761, the author believes that these multimodal behaviors might be related to the tectonic context of Sicily, which is quite interesting. It is suggested that the author conduct in-depth analysis by referring to data such as the crustal movement rate of Sicily, or at least compare the differences in error distribution between the structurally active areas (such as around Mount Etna) and the stable areas. These analyses will better support your hypothesis.

Author Response

Please see the attachment.

Best regards

Gino Dardanelli

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

he article mainly analyzes the data of the CORS station in Sicily. Although the workload is substantial, the innovation is not prominent. I suggest that the authors refine the innovation of the article. Additionally, I have the following suggestions.

1. The figure in Figure 2 (c) isnot very intuitive. Please adda detailed description of the 

2. Is it possible to conduct statistical analysis with equal sample sizes due to the significant difference in sample quantity in Figure 2 (b)?

3. Negative signs preceding "0" on coordinate axes should be removed.

4. Elucidate data in Tables 8-9, or explain potential factors contributing to weak correlations.

5. The conclusionsstates that "perhaps for the main distribution of VTRs and CORS along the east-west direction, rather than along the north-south direction." Then, can other CORS stations distributed in the north-south direction be used for verification and analysis?

6. Moreover, the phenomenon of the double peak mentioned in the text is related to factors such as ionospheric activity. Can it be verified and analyzed?

Author Response

Please see the attachment.

Best regards

Gino Dardanelli

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have responded to all the comments I have raised.

Reviewer 2 Report

Comments and Suggestions for Authors

The author's revisions and explanations have well responded to my previous comments. I believe this work has reached my personal standards for publishing a paper.

Reviewer 3 Report

Comments and Suggestions for Authors

The author made improvements and explanations to the relevant content based on the proposed suggestions. It is suggested that future research could consider conducting verification on whether the double-peak phenomenon occurs during the evening. Overall, the article has undergone many revisions and has seen significant improvements. I am satisfied with the revised manuscript.