Low-Cost BDS Reflectometry for Real-Time Water Surface Retrieval

Round 1

Reviewer 1 Report

In this paper, a real-time precision water surface height measurement method is proposed. which is based on BDS-R carrier phase. The research content of this paper is very interesting and has important theoretical and application value in the filed of remote sensing. The experiment is sufficient and conclusion is credible. It is recommended to receive after minor revision.

 

1.  What is the physical meaning of the zero in formula (9)?

2.  How to determine the threshold in formula (10)?

3.  Please show the result of the floating-point solution in the Fig.7.

4. Why is the positioning error so large in static floating-point solutions? What's the reason?

     

 

 

 

Author Response

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Reviewer 2 Report

Brief summary

 The manuscript concerns the GNSS-R technique in application to water surface height monitoring. The authors adopted the existing method and tested it using low-cost components. The proposed solution has been experimentally tested in two environments. Both experiments (land and water surface) delivered promising results suggesting the potential usability of the proposed configuration in a real application.

 Broad comments

 Both tests were conducted in very conducive conditions, so the research can be considered as the first stage of the system development. Authors – as they mentioned in the conclusions section – are aware of this fact. Nevertheless, the extended test conducted in rough water conditions can deliver the ultimate answer considering the system’s real performance. As such a test has not been conducted the authors are asked for extending the discussion by a literature study of the influence of the water undulation on the measurement results.

It could be also reasonable to give some examples of the situation where water level changes are not accompanied by a water ripple.

 Specific comments and minor mistakes

 The Figure 8 title mentions the red line which is not present in the pictures.

Author Response

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Reviewer 3 Report

I find the paper very interesting and the results seem to be valid and useful. QC proposal seems to work properly and provide high precision in altimeter measurements.

I have some small comments on the

• Line 115: I suggest to explain what authors mean with "(*)". I think it is the binary relation between equations and numbers between brackets, but it is not completely clear in the text.
• Line 133: The table is cut into two parts.
• Line 202: The title is at the end of a page.
• Figure 3 and explanations: The support seems to be made by metallic elements. Did the authors analyse the effect of this metallic support on the measurements? Would the results be better with a wooden support?
• Line 368: The title is at the end of a page.

 

I suggest to accept the manuscript with those minor changes.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

All my comments have been satisfactorily addressed. The manuscript can be accepted in the present form.

Author Response

Thanks for your comments.