Towards the Unmanned Aerial Vehicles (UAVs): A Comprehensive Review

Round 1

Reviewer 1 Report

The authors provide an overview of UAV technologies, application fields, challenges and security issues and future research directions. The paper is interesting and well written, English style and grammar are good, except for some typos (for example, "it" should read "they" on line 111, "Manuel" should read "Manual" on line 131, ref. [52] cited on line 194 is missing, "important" should read "importance" on line 209, "platform" should read "platforms" on line 227, "UE" on line 217, "FWR" in Fig. 8 and "UWPT" on line 311 are not explicited, "wire" should read "wireless" on line 316, "am" should read "an" on line 370, line 371 is not clear, ref. [105] is incomplete (journal, proceedings,...?), "complete" should read "completely" on line 701, "avalanches" should read "avalanche" on line 772, "Imaging" should read "Image" on line 779, "in" should read "is" on line 790). 

I have only two concerns. First, the title of the paper does not seem to be effective. I would suggest something like "UAV applications, challenges, security issues and future directions: a review", which, in my opinion, better describes the topics dealt with by the authors. After all, the scientific community is not going "towards" the UAVs, since UAVs represent a substantial research topic in these years.

Second, I would emphasize a little bit (perhaps adding some references) the aspects related to the integration of UAVs in the "classic" ATM space. UTM (UAV Traffic Management) is becoming a very critical issue, and a review of the main aspects related to the "UAV behavior" in the sky would be appreciated. Finally, is Figure 1 really necessary?

In conclusion, I would recommend publication after some thoughts on the above mentioned concerns.

Author Response

Reviewer #1

1. The authors provide an overview of UAV technologies, application fields, challenges and security issues and future research directions. The paper is interesting and well written, English style and grammar are good, except for some typos (for example, "it" should read "they" on line 111, "Manuel" should read "Manual" on line 131, ref. [52] cited on line 194 is missing, "important" should read "importance" on line 209, "platform" should read "platforms" on line 227, "UE" on line 217, "FWR" in Fig. 8 and "UWPT" on line 311 are not explicited, "wire" should read "wireless" on line 316, "am" should read "an" on line 370, line 371 is not clear, ref. [105] is incomplete (journal, proceedings,...?), "complete" should read "completely" on line 701, "avalanches" should read "avalanche" on line 772, "Imaging" should read "Image" on line 779, "in" should read "is" on line 790). 

Response:

We sincerely thank reviewer for kind information and highlighting all these points. Considering the valuable feedback, we have made all the relevant corrections in revised manuscript. 

2. I have only two concerns. First, the title of the paper does not seem to be effective. I would suggest something like "UAV applications, challenges, security issues and future directions: a review", which, in my opinion, better describes the topics dealt with by the authors. After all, the scientific community is not going "towards" the UAVs, since UAVs represent a substantial research topic in these years.

Second, I would emphasize a little bit (perhaps adding some references) the aspects related to the integration of UAVs in the "classic" ATM space. UTM (UAV Traffic Management) is becoming a very critical issue, and a review of the main aspects related to the "UAV behavior" in the sky would be appreciated. Finally, is Figure 1 really necessary?

Response:

We are greatly indebted to reviewer for his kind feedback. We have revised manuscript’s title accordingly. We have added discussion about UTM in subsection 3.5 along with reference literature. Moreover, we have removed figure 1 as well.

3. In conclusion, I would recommend publication after some thoughts on the above mentioned concerns.

Response:

Thank you for kind instruction. We have made relevant changes in revised manuscript.

In addition to above listed changes, we have made several writing corrections to improve the quality of this work. We have revised diagrams with better resolution quality for better readability. We have carefully defined full form of all abbreviations at first of appearance.

Reviewer 2 Report

I very much like the topic and overall spirit of this manuscript, yet found myself heavily engaged in line-by-line editing for grammar and wording. I stopped after reviewing 2 pages after concluding that another go at editing is needed for the paper to get a proper peer review. I very much look forward to reviewing this once those edits are made as the topic is of great value.

Please see attached document with comments/highlights in the manuscript

Comments for author File: Comments.pdf

Author Response

Reviewer #2

1. I very much like the topic and overall spirit of this manuscript, yet found myself heavily engaged in line-by line editing for grammar and wording. I stopped after reviewing 2 pages after concluding that another go at editing is needed for the paper to get a proper peer review. I very much look forward to reviewing this once those edits are made as the topic is of great value.

Response:

We sincerely thank reviewer for kind feedback. We have fully revised this manuscript and made all the possible corrections in this revised draft.

Reviewer 3 Report

Interesting review in a decently drafted manuscript that needs some mild revisions.

·        The manuscript is clear, relevant for the field and presented in a well-structured manner. The cited references may be classified as "older" with some inclusion of more current references (within the last 5 years). The reviewer has made recommendations to ameliorate. The manuscript is scientifically sound. The manuscript’s results are reproducible based on the details given in the methods section. The figures/tables/images/schemes appropriate and properly show the data with some mandatory improvements necessary. They are easy to interpret and understand, but require improved presentation. The references are interpreted appropriately and consistently throughout the manuscript, although the English language is a bit rough in places. The conclusions are consistent with the evidence and arguments presented.

Abstract is okay but is not likely to entice a broad readership to continue reading the rest of the manuscript.

·        Importance of the critical concerns are omitted, leaving the reader without a reason to continue reading. The results are only presented in weak, qualitative fashion. "…identifying research gap and presents future research directions regarding UAVs….” is very weakly stated results lacking any hint at potential improvements that might derive from the advised research directions leaving the reader without a prioritization of which recommendation to pursue themselves.

Introduction is decently done with some omitted very recent literature and some very mild abuse of multi-citation without elaboration (merely a few double-citations…very acceptable, requiring no revisions).

·        Shortest-distance optimization is referenced with Kim et al.’s work on navigation for efficient battery usage, while a min-control optimization reference seems more logical but is omitted (e.g. “virtual sensoring of motion using Pontryagin’s treatment of Hamiltonian systems”).

·        Highlighting the scope and contributions in a dedicated paragraph is very effective.

·        Narrowing the intended readership to UAV-enthusiasts could be avoided, since the manuscript opens with a decently broad motivation (e.g. intended usage by DHL, Amazon, etc.).

·        The complete review of anticipated attacks (by itself) would highly motivate non-UAV enthusiasts, broadening the potential readership.

Equations are omitted completely, while that is not unusual for a Review manuscript.

Figures are decently created but poorly presented with some mandatory improvements to ensure the readership has access to the content.

·       ·        Figures are fuzzy/blurry and must be improved.

·        ·        Internal font size is occasionally too small especially combined with fuzziness to make the font difficult to read (figure 16 is particularly egregious). 

·        ·        Figures 5 & 7 are very effective and strongly lends the applicability of the manuscript’s content.

·       ·        Line styles and sizes are identical in figures 8 & 9 rendering the disparate data indistinguishable when the manuscript is read in printed hardcopy (particularly in black and white) negating the value of the figures due to reliance on colors.

·       ·        Is figure 14 meant to imply nine UAV’s as depicted are required for power line inspection?

Tables are decently done.  

·        Inclusion of a table defining variables and acronyms in an appendix is welcome and effective. Please add such. 

Survey of issues and challenges is highly focused on communications limited to mostly older publications with a few from post 2017, while the manuscript title claims to be a “comprehensive review”. Amelioration can be accomplished in either section 2 or section 8. Avionics for GNC omitted deterministic artificial intelligence (originally in 2020 developed for unmanned underwater vehicles, but subsequently proposed by [Miller] in 2021 for electric circuits and by [Shah] for DC motors that same year. Next [Osler] in 2022 proposed application for remotely operated vehicles and that same year by [Sandberg] for autonomous spacecraft).

Author Response

Reviewer #3

1) Interesting review in a decently drafted manuscript that needs some mild revisions.

The manuscript is clear, relevant for the field and presented in a well-structured manner. The cited references may be classified as "older" with some inclusion of more current references (within the last 5 years). The reviewer has made recommendations to ameliorate. The manuscript is scientifically sound. The manuscript’s results are reproducible based on the details given in the methods section. The figures/tables/images/schemes appropriate and properly show the data with some mandatory improvements necessary. They are easy to interpret and understand, but require improved presentation. The references are interpreted appropriately and consistently throughout the manuscript, although the English language is a bit rough in places. The conclusions are consistent with the evidence and arguments presented.

Abstract is okay but is not likely to entice a broad readership to continue reading the rest of the manuscript.

Response:

We acknowledge and appreciate reviewer for this valuable suggestions. We have tried our best to improve the quality in revised manuscript considering above points.

2) Importance of the critical concerns are omitted, leaving the reader without a reason to continue reading. The results are only presented in weak, qualitative fashion. "…identifying research gap and presents future research directions regarding UAVs….” is very weakly stated results lacking any hint at potential improvements that might derive from the advised research directions leaving the reader without a prioritization of which recommendation to pursue themselves.

Response:

Thank you for kind information. In revised draft, we have added few more future research directions which can be develop interest of its readers for future works.

3)  Introduction is decently done with some omitted very recent literature and some very mild abuse of multi-citation without elaboration (merely a few double-citations…very acceptable, requiring no revisions).

Response:

Thank you for kind remarks. We have added some discussion to improve the quality in revised draft.

4) Shortest-distance optimization is referenced with Kim et al.’s work on navigation for efficient battery usage, while a min-control optimization reference seems more logical but is omitted (e.g. “virtual sensoring of motion using Pontryagin’s treatment of Hamiltonian systems”).

Response:

Thank you for sharing a very good relevant article. We have added some discussion and cited this article as well.

5) Highlighting the scope and contributions in a dedicated paragraph is very effective.

Response:

Thank you for your kind remarks.

6) Narrowing the intended readership to UAV-enthusiasts could be avoided, since the manuscript opens with a decently broad motivation (e.g. intended usage by DHL, Amazon, etc.).

Response:

Thank you. In revised draft, we have tried to remove such limitations and concerns.

7) The complete review of anticipated attacks (by itself) would highly motivate non-UAV enthusiasts, broadening the potential readership.

Response:

We sincerely thank reviewer for kind information and highlighting this key point. We have tried to present contents keeping both UAV-enthusiasts and non- UAV-enthusiasts into consideration.

8) Equations are omitted completely, while that is not unusual for a Review manuscript.

Response:

The reviewers' opinions are valuable to us. On the other hand, adding equations is not currently feasible. We are working on a new review article in which we will take these suggestions into account. At the same time, we agree that including equations may significantly increase the article's quality.

9) Figures are decently created but poorly presented with some mandatory improvements to ensure the readership has access to the content.

Response:

We appreciate and acknowledge for highlighting this key point for better readability of its readers. We have provided figures with high resolution and proper discussion to make it clear for readers.

10) Figures are fuzzy/blurry and must be improved.

Response:

We have made relevant changes considering this kind instruction. Figures with high resolution are provided in revised draft.

11) Internal font size is occasionally too small especially combined with fuzziness to make the font difficult to read (figure 16 is particularly egregious). 

 Response:

We have improved figures quality in revised manuscript.

12) Figures 5 & 7 are very effective and strongly lends the applicability of the manuscript’s content.

Response:

Thank you for kind appreciation.

13) Line styles and sizes are identical in figures 8 & 9 rendering the disparate data indistinguishable when the manuscript is read in printed hardcopy (particularly in black and white) negating the value of the figures due to reliance on colors.

Response:

We agree with the reviewer. We have made relevant changes considering this important point.

14) Is figure 14 meant to imply nine UAV’s as depicted are required for power line inspection?

Response:

No. In order to remove this ambiguity, we have changed this figure in revised manuscript.

15) Tables are decently done.  

Response:

Thank you for kind appreciation.

16) Inclusion of a table defining variables and acronyms in an appendix is welcome and effective. Please add such. 

Response:

As we have defined each variable at its first place of appearance so readers will not face any issue. In our opinion, there is no need to add additional Appendix as each abbreviation is already defined.

17) Survey of issues and challenges is highly focused on communications limited to mostly older publications with a few from post 2017, while the manuscript title claims to be a “comprehensive review”. Amelioration can be accomplished in either section 2 or section 8. Avionics for GNC omitted deterministic artificial intelligence (originally in 2020 developed for unmanned underwater vehicles, but subsequently proposed by [Miller] in 2021 for electric circuits and by [Shah] for DC motors that same year. Next [Osler] in 2022 proposed application for remotely operated vehicles and that same year by [Sandberg] for autonomous spacecraft).

Response:

Thank you for your valuable instruction. We have added relevant discussion along with references such as reference [126] and [127] in Section 8 in revised manuscript.

In addition to above listed changes, we have made several writing corrections to improve the quality of this work. We have revised diagrams with better resolution quality for better readability. We have carefully defined full form of all abbreviations at first of appearance. We have added new subsection 3.5 UAV Traffic Management (UTM) and added sufficient details in Future Research Directions.

Round 2

Reviewer 2 Report

This was a very well-researched paper, and very informative in terms of UAS developments outside of the realm of the remote sensing UAS applications that I'm used to. I also found the many figures to very nicely convey the topics being covered.

I normally do not spend as much time providing the detailed edits that I have provided but did so given what I see as the quality of the research literature review conducted, along with the structure. This structure did, however, somewhat fall apart beginning at line 650. Why suddenly did the format change to everything bulleted? 

Please review my suggestions and comments and make changes as you deem fit between you and the editors. In terms of research, science, and contribution, I very much enjoyed the article and hope the changes will allow for it to be published soon.

Comments for author File: Comments.pdf

Author Response

We are much indebted for the insightful review and productive suggestions of our manuscript (ID 1756990). As stipulated, we have incorporated the suggested amendments for further honing the research work. The revised manuscript is, we hope, an enhanced version. Reviewer comments have been carefully addressed. We worked on the structure, and as far as we can see, the article now flows well from beginning to end. We have also revised the write-up following an extensive grammatical check. Attempts have been made to assure spontaneity and lexical beautification. We are hopeful that the revised version will make it to the final acceptance stage.

Author Response File: Author Response.docx