Preliminary Design of an Unmanned Aircraft System for Aircraft General Visual Inspection

Round 1

Reviewer 1 Report

This research developed a global and/or zonal general visual inspection (GVI) procedure implemented by means of an autonomous unmanned aircraft system (UAS), equipped with a low-cost, high-definition camera for conducting damage detection of panels. The employed UAS also has a series of distance and trajectory sensors for obstacle avoidance and inspection path planning. The reviewer believes that the current version of the manuscript is not yet ready for publication; the authors are encouraged to consider the following comments and suggestion and revise the manuscript accordingly.

1. The authors should consider streamlining the manuscript to make it more concise. Also, the authors should consider splitting the Introduction section into two sections, including an Introduction section and a Background section. The introduction section should focus on introducing the research objectives and the research questions that need to be addressed, while the Background section should focus on literature review of related work and defining the research gap. In addition, the authors should carefully review their grammar and spelling before the submission. The authors also need to conduct more detailed literature review. For example, UAS also has been used for pavement surface visual inspection (Characterizing pavement surface distress conditions with hyper-spatial resolution natural color aerial photography, Zhang et al. 2016).

2. The authors should have a researcher that has a photogrammetry or remote sensing background to review the manuscript for using the appropriate terms. For example, in Table 2, the authors mentioned that the sensor resolution, pixel size, etc. However, in remote sensing and photogrammetry, pixel size should be sensor size and detector size. In addition, what resolution do you refer to? There are four resolutions, including spatial resolution, spectral resolution, temporal resolution, and radiometric resolution. It is more useful to talk about these resolutions for the imagery collected. Also, in remote sensing, unmanned aircraft systems (UAS) instead of unmanned aerial vehicles are often used when sensors attached. The authors should be careful with using different terms.

3. As the authors stated, GVI involves visual examination of an interior or exterior area within touching distance and under normal lighting condition, hangar lighting, flashlight or drop-light. What lighting condition is the experiment in? Is the system compatible with all possible conditions? The authors need to elaborate on this.

4. All figures needs to be revised to make them more legible. For example, in Figure 1, the authors should make sure they have the copyright to reuse the figures. In addition, in Figure 12, the reviewer cannot read anything in the printed manuscript. The reviewer has to zoom in to 200% to read them. Revise all figures and please create vector images if necessary.  In addition, the reviewer believes the authors should use Figure (a) and (b) to indicate different part, instead of using left and right. Table 1 also needs to be revised. The layout of the table makes the reviewer think the table is not necessary.

5. The authors should include an appendix section to document the tools and process used for this research to assist researchers to want to repeat the research for their study areas.

Author Response

answers are contained in the attached file

Author Response File: Author Response.pdf

Reviewer 2 Report

Overall I think this paper offers a novel and interesting technique which has well-justified value to the community.  My major concern with this work though is its maturity.  I think the results are underdeveloped, and a bit more validation of the technique needs to be done before it merits publication in a journal.  To me, this feels more like a conference paper that will later be developed into a journal article.  In addition to this major concern, I have the following comments to help improve the work:

1) Typo line 21

2) Grammar issue on line 32

3) The statement on lines 55-57 is critical to motivating your work.  I think this could be emphasized/developed even further to really drive home your point.  Something along the lines of how important false negatives are in this context.  I.e., false positives are not really a major concern, but missing defects could be catastrophic

4) The organization of Table 1 could be improved.  Perhaps a column for altitude, endurance, payload, etc.?  Right now it isn't really a table, just a list with lines in between

5) The paragraph from lines 79-93 is well-written, but I think it could benefit from more citations to support these statements

6) The formatting of equation (1) should be improved.  Also, I do not think sufficient information is provided as to how this information is obtained when implemented.  Is there a temperature/humidity sensor on the aircraft?  Ground control station?  How is this information incorporated into the algorithm?

7) There isn't enough information provided about the sensing/estimation/detection techniques

8) I think Figure 8 is unnecessary.  Arduino mega is a common microcontroller, especially for readers of this journal.  If someone would like to see it, they can look it up.

9) Figure 12 is weak, and I do not follow its purpose/intent

10) There is a significant amount of work laid out in lines 279-293.  I think more of these ideas need to be implemented before a publication is merited

Author Response

The authors thank you for the reviews. answers are contained in the file attached

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have addressed all my comments.     

Reviewer 2 Report

The revisions have significantly improved the quality of this work.