Review Reports

Round 1

Reviewer 1 Report

I thank the authors for responding my suggestions and modifying the manuscript accordingly. Particularly, I appreciate the Discussion has been reinforced by including comments regarding to possible limitations of the methodology due to atmospheric conditions changing and vertical movements of the water masses.

 

I have only a few additional suggestions:

-Line 25. The idea written in the sentence commencing with "Research is needed ..." has been expressed previously. This sentence can be deleted. Similar comment for line 32 ("USVs and UASs ...".

 

-Lines 80-90. I will expect that the authors formulate more exactly which specific problem is going to be approached.

 

-Repetition of results should be avoided in the Discussion (lines 276-279, 284-286, 308-312, 325-332.

 

Author Response

Thank you for taking another look at the manuscript and providing additional revisions. Comments below:

-Line 25. The idea written in the sentence commencing with "Research is needed ..." has been expressed previously. This sentence can be deleted. Similar comment for line 32 ("USVs and UASs ...".

Response: The changes have been addressed as suggested.

 

-Lines 80-90. I will expect that the authors formulate more exactly which specific problem is going to be approached.

Response: This has been rewritten to highlight the problem.

 

-Repetition of results should be avoided in the Discussion (lines 276-279, 284-286, 308-312, 325-332.

Response: These sections have been deleted or modified to avoid repetition.

Reviewer 2 Report

In the Abstract part, the very long sentence. Please break it into shorter sentences. 

For the Introduction Section, more extensive literature research should be conducted.

The conclusion is a little redundant and should be further condensed.

Besides, the language needs to be improved. 

 

Author Response

Comments below:

In the Abstract part, the very long sentence. Please break it into shorter sentences. 

Response: This sentence has been modified.

For the Introduction Section, more extensive literature research should be conducted.

Response: Additional references have been added.

The conclusion is a little redundant and should be further condensed.

Response: Large sections of the discussion have been removed for brevity and to avoid repetition.

Besides, the language needs to be improved. 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

please see attached.

Comments for author File: Comments.pdf

Author Response

Please see the attached report.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors presented a methodology for analyzing the surface distribution of a dye in a marine area based on drone images, which would be useful to monitor the distribution almost in real-time of hazard substances. The research is fairly sound from a technical viewpoint and with high potential applicability; furthermore, the manuscript is well written. However, I am afraid it does not ensure the interest of the readers in its present form because the text lacks an actual discussion about pros and cons of this technology applied to open sea. For instance, I wonder which the performance of these techniques would be under different atmospheric and hydrological conditions or if they can be used to infer substance transport not just at the surface. The discussion as presented appears to be a repetition of the methods and results. I think that the manuscript will be useful for publication provide a good discussion is written.    

Other queries:

Lines 80-83. Please, to justify why this area was selected to do the experiment. Additionally, a description of the hydrological and atmospheric conditions occurring during the experiment should be written here, including all information that would be relevant in determining the transport of the dye (weight of the waves, vertical structure of the water column) or the color signal (photosynthetic pigment concentration).

Lines 97-104. Note that the ocean is a three-dimensional system. Consequently, vertical transport would be occurring. I wonder, which the optical depth captured by the drone is.

Lines 238-278. These paragraphs can be deleted since they offer information that has been shown previously.

Lines 283-286. These sources of error have to be discussed more extensively.

 

 

 

Author Response

Please see the attached report.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors provide a promising technique with valuable measurements for tracking the movement of a surrogate hazardous agent in a coastal ocean environment and estimating its concentration based on drone images. Overall, the article is well-written and easy to follow with few exceptions. I personally, enjoyed reading this interesting article. Still, few minor issues remain, and this research will be ready for publication.

The authors have done a nice job of framing a problem and investigating it across many sources of information. My question, did you consider the velocity and direction of the oceanic currents in your experiment? This will affect the location and time of sampling as well.

The paper has less of literature review with only 15 citations. I recommend consider more of pervious conducted work and other approaches.

Lines 42 and 44: Add areas of study.

Figure 1: Add stretch color legend or make the classification includes all the represented colors on the map. Add lat. Long. Coordinates to the map.

Line 89: correct “SystEm” to “System”

Figure 2: the figure doesn’t have meaning without coordinates and scale bar.

Line 156: rewrite this sentence in a better way.

Figure 6a: Add lat. Long. Coordinates, scale bar with N arrow to the map.

Figure 10 a and b: Add lat. Long. Coordinates, scale bar with N arrow to the map.

Figure 11 a and b: Add lat. Long. Coordinates, scale bar with N arrow to the map.

Figure 12 a and b: Add lat. Long. Coordinates, scale bar with N arrow to the map.

 

 

 

 

Author Response

Please see the attached report.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The updated manuscript is largely improved on its Introduction and references, figure quality, and some text writing.

I really appreciate the idea of using UAV for ocean studies, but the authors may need to view the data from another perspective to show its value, rather than a remote sensing dye concentration modelling. I feel the result presented by this work at its current stage does not stand on a scientifically strict design and analysis as a remote sensing study.

Water has very weak reflectance therefore stricter measurement is critical for water constituent concentration modelling. for instance, key result in Fig8, the dye difference is visually caused by the glint at the corner in (a), not the altitude. Rhodamine concentration modelling is only meaningful when the input signal is valid or at least well-reasoned(e.g., averaging). Some better understanding about optical oceanography experiments such as works by Dr. Lee also at Massachusetts (https://www.umb.edu/faculty_staff/bio/zhongping_lee) would largely increase the credibility of this work.

My major concerns are still unresolved in this updated version:

1) the reasoning of why large effort given on photogrammetry processing is not clear to me. Fig5,8-10 all present a single image processing. adding coordinates to such image is trivial for the subjective (dye concentration). If the author is to produce a dye map covers entire region of Fig.2, then photogrammetry is required.

2) for Result1, in Fig6, the Mean red ratio may severely affected by glint(Fig8), shadow(Fig.5), or possibly uneven vertical distribution of dye(Fig.9). A lot more work is needed on this ratio value before it can be used to further link with measurements of dye.

3) Result 2 the altitude change impacts the dye concentration. as mentioned above, in Fig8 the difference mostly caused by glint at the corner when inspected visually, not by altitude.

In summary, it is quite an innovative and interesting idea to conduct such a study. But at the current stage, is does not satisfy a good remote sensing inverse modelling. I would be glad to read the work from the authors after some fundamental update on experiment and processing.