Refraction Correction for Spectrally Derived Bathymetry Using UAS Imagery
Round 1
Reviewer 1 Report
The manuscript submitted by the authors dealing with the bathymetric mapping of shallow water is interesting and well written. However, before it could be considered for publication, the authors should revise it and improved it accord to below comments and suggestions:
Lines 182-184: As the present manuscript is technical paper, the authors should clearly demonstrate how the values of m1, m2, m3, m4 parameters were obtained by linear regression.
Lines 233-234: Due to problems that arise from georeferencing and large ortho-mosaic image creation over dynamic sea and ocean waters, the authors should discuss the applicability of the proposed methodology, for the studies conducted on large areas. How good-quality georeferenced orthoimages could be obtained while there is no use of ground control points? What is the effect of waves and tides on this SDB?
Lines 248-253: the authors should provide maps indicating the location of both training, testing and validation points.
Lines 262-263: please provide the software used for the processing of the orthoimages using Stumpf algorithm and the proposed modified version.
Line 267: It could be interesting to make the comparison of the results obtained using Stumpf algorithm and the proposed modified version on orthoimages and their test on freely available satellite images as it was mentioned in the conclusions on the lines 375-376.
Line 284: the authors should provide maps with some contours indicating the variation of water depth. This would help readers appreciate the quality of the results.
Lines 24-25: Please provide references of recent works conducted using Photogrammetric and optical satellite remote sensing methods for mapping bathymetry in nearshore coastal areas. Please refer to (1) Muzirafuti, A.; Crupi, A.; Lanza, S.; Barreca, G.; Randazzo, G. Shallow water bathymetry by satellite image: A case study on the coast of San Vito Lo Capo Peninsula, Northwestern Sicily, Italy. In Proceedings of the IMEKO TC-19 International Workshop on Metrology for the Sea, Genoa, Italy, 3–5 October 2019; (2) Rossi, L.; Mammi, I.; Pelliccia, F. UAV-Derived Multispectral Bathymetry. Remote Sens. 2020, 12, 3897. https://doi.org/10.3390/rs12233897
Minor editing of English language required
Author Response
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Author Response.docx
Reviewer 2 Report
The overall quality is regular. The biggest fault is the lack of a comparison with a real bathymetry (at least a single beam bathymetry). The current presentation with only two sites, without reference bathymetry, needs to be strongly improved (more relevant study sites).
English language fine. No issues detected
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
The subject is often simplified and not taken into account. Discussing it with respect to drone based sensors or satellite sensor is of great importance for the community.
lines 117-129: Could you further comment ont the sun angle illumination. Could you further explain why the assumption of using only the seabed to camera path is enough.
line 152-line 156: Why not carrying over the polynomial regression.
line 170: a closing parenthesis in the ln quotient
line 223. Wondering if you should furhter introduce the SfM principle (although I understand it is not the heart of the paper). The rationale behind this suggestion is that when comparing two datasets the reader might be interested in the origin of the both datasets.
line 281: I am not fully aware of the Liliefors test. You might want to further introduce it. Or at least quote a theoretical reference.
Figure 8/9. You should display the color scale for all sub-figures. Also I suggets that you use the same range or errors/difference in errors so that all figures are comparable.
Author Response
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Reviewer 4 Report
The study presented for review deals with the important issue of knowing the detailed shape of the bottom of water bodies. Remote sensing has been playing an important role in the knowledge of bathymetry for some time. Thus, the study proposed by the authors is part of this trend. I recommend the report for publication after taking into account the following comments.
The information that affects the results obtained is not enough for me. Please provide more details on humidity, wind speed, wave height, etc. How would the results obtained be presented if the above variables were different from the day of measurements?
"Little sediment or plankton in the water column or on the water surface"- meaning how much? Please cite specific values.
Chapter Discussion needs a major overhaul. Currently, it does not refer to any other publication. The reader gets the impression that the authors are discussing with themselves.
Line 282: () ?
The Conclusion chapter should clearly and precisely summarize the most important achievements of the research conducted.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
No further comments
Minor editing of English language required
Reviewer 2 Report
The authors made a good revised version. In the present form can be accepted.
