The Design and Evaluation of a Direction Sensor System Using Color Marker Patterns Onboard Small Fixed-Wing UAVs in a Wireless Relay System

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper presents a technically sound and well-motivated study, but real-world validation is needed. Following are my comments for the authors:

 

- The paper would benefit from a comparative evaluation with alternative methods, such as deep learning-based marker detection. The discussion on limitations and environmental robustness should be expanded, and computational efficiency and implementation feasibility of UAV hardware should be addressed.

 

Sections Wise Comments:

Abstract: 

Include quantitative performance results (e.g., detection accuracy, resolution limits, motion blur tolerance, etc).

Also, the authors should compare the proposed method’s efficiency with existing techniques (e.g., RF sensors, AR markers).

Clarify the primary contribution—how this method improves over conventional methods.

 

Introduction:

Expand the discussion on UAV applications in wireless relay systems with more references as the current references are too few to be justified for a research paper.

Provide a clearer comparison between marker-based and non-marker-based approaches, emphasizing trade-offs.

Briefly mention the potential challenges of using color markers in real-world scenarios (e.g., environmental conditions).

The authors should clearly define the research gap the study aims to fill.

 

Conventional Direction Detection Technology:

Discuss real-world challenges of non-marker-based methods, such as signal interference, equipment costs, and dependency on external transmitters.

Authors should expand on why AR markers perform poorly in motion-blurred conditions by adding a comparison with other researchers' work.

 

Experiments:

Authors should conduct at least a basic real-world UAV flight test to validate system performance outside of a lab environment, as the prototype they are showing is fixed on a testing fixture.

They should also discuss how exposure time variations might affect motion blur robustness.

Another aspect is to evaluate the impact of different lighting conditions on marker detection accuracy.

They can address potential inaccuracies in the ArUco marker-based pose estimation and their effect on results.

 

Results and Discussion:

Expand the discussion to include failure cases (e.g., occluded markers, extreme motion blur, changing light conditions).

Compare the proposed method’s performance with other existing methods (either from literature or a simple experiment).

Discuss the practical limitations of the system, such as its reliance on controlled marker placement.

 

Conclusion:

Authors should clearly state the limitations of the proposed approach and how they might be addressed in future work.

Discuss the potential for integrating deep learning for improved marker recognition.

Mention future improvements in hardware implementation to optimize onboard processing.

 

References:

The authors should add references supporting claims made in the introduction and technology review sections.

Include more recent citations on UAV-based optical tracking and wireless relay systems.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper is interesting and addresses a significant problem, especially for those applications related to disaster recovery operations.

I suggest its publication, after some improvements. Especially in the bibliography and from the side of the language: in the current form, it potentially distracts the reader from the technical content. 

Section 1: Extend with references to recent reviews about nav-assisted wireless communications 

Section 2: It is well detailed, but a more detailed discussion about the limits of approaches 2.1 ad 2.2 would be helpful to the reader

Section 3: Elaborate on the computational costs of the method on board, since energy saving on the UAV is fundamental

Section 4: Discuss the reason for choosing the 5.8 Ghz frequency. Discuss the possible alternative frequencies that could be implemented for disaster recovery operations in such a system and impact on the implementation of the method. About the antenna, a dish with 30 cm diameter might be difficult to handle on board. Discuss the potential limitations of the chosen antenna and its impact on the UAV.

Section 5: the experiments are well described but probably this is the section needing the strongest effort to improve the language

Section 6, Conclusions: analyse the possible problems arising from the application in a real UAV of the method tested for the moment only in laboratory 

Bibliography is too essential. It should be improved. There are recent comprehensive reviews about the UAV-assisted wireless communications that should be referenced in the paper. Example: https://doi.org/10.1016/j.comcom.2023.05.013

On the contrary, many items should be removed. References 9 and 10 are pure commercial and should not be inserted in a research paper. References 12 and 13 are much worse: authors write in the text "buy a raspberry pi", since it is the selling page from the manufacturing company. A research article should never contain an invitation to buy a product. These 9, 10, 12 and 13 are not needed and must be removed.

English is understandable but here and there should be significantly improved. Example, but not unique: first paragraph of section 5.

Also, uniform the verbal tense to describe the performed research activity:  one between past and present should be chosen and maintained. At the moment there is high confusion, as the two are mixed. Example, but not unique: there is a continuous mix in section 5.1. One possible suggestion is to use  the past for all actions done by the researchers, the present for the rest.

Row 42: double space detected

Comments on the Quality of English Language

English is understandable but here and there should be significantly improved. Example, but not unique: first paragraph of section 5.

Also, uniform the verbal tense to describe the performed research activity:  one between past and present should be chosen and maintained. At the moment there is high confusion, as the two are mixed. Example, but not unique: there is a continuous mix in section 5.1. One possible suggestion is to use  the past for all actions done by the researchers, the present for the rest.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The response provided by the authors seems relatively trivial.

I have highlighted so many points, and the author's responses are quite confusing they are ignoring some of the comments and only making changes that they think are needed for the suggestions I have provided.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

No Further Comments