Innovative Maritime Uncrewed Systems and Satellite Solutions for Shallow Water Bathymetric Assessment

Round 1

Reviewer 1 Report

 The current manuscript deals with the analysis and comparison of several methods for assessing shallow water bathymetry using maritime unmanned systems integrated with advanced sensors such as Light Detection and Ranging (LIDAR) and multibeam echo-sounder (MBES). It also describes Satellite-Derived Bathymetry (SDB) techniques within the same geographical area. The article is interesting and relevant, however, some review comments should be addressed before acceptance as follows:

1- Starting from the introduction, the main research motivations and contributions are unclear, and further improvements are requested.  A bullet list outlining the gaps and main contributions of the paper should be added to the end of the introduction section followed by an outline of the rest of the paper. This can make the reader more at ease in understanding the main theme of the paper. 

2- When using the  MUS and sensors in shallow waters can be challenging because of varying water depths, currents, waves, marine debris, etc. Accurate navigation and positioning are very essential. How did the author solve this problem? Please discuss!

3- It is well-known that water clarity might affect the performance of e LIDAR. factors like algae bloom, turbidity, and color-dissolved organic matter might impact the depth penetration and overall precision. How did the authors deal with these issues during the measurements? Please discuss!

4- Accurate depth measurement in shallow waters with MBES necessitates meticulous calibration, while adequately accounting for nearfield effects and refraction demands accurate modeling. Were these factors included in the study?

5- The duration and frequency of surveys are affected by frequent adverse weather conditions in shallow coastlines and the absence of infrastructure for launching and recovering MUS. How the weather factors have been included in this study?

6- The presence of murky waters in shallow estuaries can diminish or entirely absorb optical and acoustic signals over short distances, consequently restricting the extent of coverage. How this issue is addressed in the current study?
7- It is recommended to obtain necessary copyright permissions in case of copying images from other sources.

8- Major achievements, challenges, innovations, and recommendations can be further addressed in the discussion section. 

9- Future scope can be further illustrated in the conclusion section. 

There are mixed usages of tenses along the paper. When starting with the present tense, it should be used along the paper, whereas the past tense can used when citing previous research works. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript presents a study comparing different methods for rapid shallow water bathymetric mapping, including satellite imagery analysis, aerial LIDAR surveys from a UAV, and multibeam sonar surveys from a USV. The study was conducted as part of a NATO research exercise focused on maritime unmanned systems and rapid environmental assessment.

1.       The introduction provides a good background but is missing some key recent references on using unmanned systems for bathymetric mapping. Consider adding some references from the last 1-2 years. The introduction lacks clear articulation of the knowledge gaps this study aims to address. What new insights is this study providing into rapid, unmanned bathymetric mapping? More context is needed on prior work using unmanned systems for bathymetry. The introduction should position this work relative to the state of the art.

2.       The materials and methods section provides more specifics on the sensors used - exact models, operating frequencies, etc. This will allow for a better evaluation of the results.

3.       The datasets comparison section focuses mainly on vertical accuracy. Consider expanding the analysis to also look at horizontal accuracy between datasets. This could reveal issues like systematic offsets.

4.       More information is needed to justify the selection of these specific equipment/sensors. What are the key capabilities? Limitations?

5.       Details on survey parameters, data processing, and analysis methods are lacking. This limits reproducibility.

6.       Provide more specifics on how data accuracy was assessed. The methodology for error quantification should be clearly described.

7.       More visualisations like difference maps should be included to reveal spatial patterns of errors.

8.       Accuracy assessment relies only on comparison to the reference survey. Independent in situ measurements should be used to further validate accuracies.

9.       Lacks a critical assessment of limitations - technology, methodology, personnel, operational, etc. These must be addressed for studies of this nature.

10.   Broader impacts are not discussed. Elaborate on how this work advances bathymetric mapping capabilities.

11.   The concluding remarks are quite short, given the extensive study presented. Expand this section to provide more concrete conclusions and recommendations based on the specific findings.

12.   Check figure captions - some seem to be missing figure numbers (e.g. a & b).

13.   Standardise the formatting of references. Some use full first names; others use initials only.

14.   Were the same sound velocity profiles used for all multibeam datasets? If not, could this be a source of some depth discrepancies?

15.   For the LIDAR data, what waveform processing methods were used? How were water surface returns discriminated?

16.   Could the USV and UAV systems be deployed concurrently for maximum efficiency in the future? What would be the limitations?

17.   Axis labels and tick mark values on several plots are too small to be easily readable (ex., Figures 7, 9, 11). The font size needs to be increased.

18.   Some figures lack descriptive captions explaining the full context of what is shown (e.g., Figures 5 and 12). Captions should allow figures to stand alone.  

While the technical language itself is satisfactory, the quality of the English writing and attention to detail regarding grammar, usage, and formatting inconsistencies diminishes the scholarly impact. Comprehensive proofreading followed by refinement of the language usage is recommended to improve clarity and readability at a level expected for peer-reviewed publication.

1.       The qualitative language used to describe differences between datasets is vague (e.g. "evident discrepancies"). Quantitative statistics are needed.

2.       Word choice could be more exact/technical in parts to reflect the scientific nature (e.g. using "obtained" vs "took").

3.       Abbreviated terms/acronyms should be spelt out fully at first use (e.g. SDB, UAS). 

4.       There are a number of typos, spelling inconsistencies, and formatting issues, indicating that more careful proofreading is needed:

5.       Figure labels vs captions do not always match (ex. Figure 10)

6.       The same term is sometimes spelled differently (LIDAR vs LiDAR) 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I would like to thank the authors for their detailed response and for addressing the review comments. The paper can be accepted after addressing one minor review comment related to the introduction section and my first comment (comment 1). The authors did not grasp the meaning of the comment. The aim is to help readers fully grasp the motivations and innovations of your work. Hence, please remerge your lengthy bullet list and just write a shorter version similar to the following:
1- The main research gaps and motivations

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2- The main contributions:
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Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have addressed the reviewer's comments in a systematic way and significantly improved the manuscript. The revisions should meet the requirements for publication now. 

Author Response

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Author Response File: Author Response.pdf