A Novel Dense Full-Field Displacement Monitoring Method Based on Image Sequences and Optical Flow Algorithm

Round 1

Reviewer 1 Report

the study investigators to use camera images for monitoring of structures. the study was written and organized well, but, the following comments may improve this study:

• the introduction is weak in the parts of image processing and used the images in the structural health monitoring (SHM).
• Previous studies that used images for monitoring structures, as well as satellite images, should be presented and discussed.
• the introduction scientific and fellow are weak and should be improved, please check, it is hard to read.
• in the test section; the main point is not studied in this paper, the distance from the camera to object should be presented and discussed. it is known that it is the main factor for the accuracy and pixels analysis. in this point, the author presented that "There are many researches on camera calibration, and the corresponding theory and application are relatively mature. In this paper, the calibration method of Zhang Zhengyou was used directly, and will not explain it in detail [35-37]", reference 37 is not for Zhang?
• flowchart of the Matlab algorithm is needed.
• the results are presented in time domain analysis, in SHM, the time and frequency domains are needed, so how this study can be improved to evaluate structures in the frequency domain.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript presents results from an investigation of the displacement monitoring method using image sequences and optical flow algorithms. While the topic is interesting and the model has some merit, the overall manuscript needs more additional work to rise to the level of publication in the applied sciences journal in the opinion of this reviewer. Below are just some minor comments and suggestions for improvement.

General Comments:

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1. The introduction was very long. It should be divided into two sections: Introduction and literature review. Please consider rewriting and clarify the motivation, objectives, and significance of this study.
2. The objective statements are rather vague and lack projected outcomes or how the paper will assist practitioners.
3. More descriptions of the test results should be improved, and more in-depth analysis should be added. The quality of the figures must be improved.
4. Your conclusions are not well supported by your experimental data and analysis. Please clearly list the new, key findings supported by the experimental investigation. The conclusions should be modified after revision.
5. The aspects of novelty of the paper must be pointed out more clearly due to the importance and complexity of the subject addressed in the work, particularly in the abstract and concluding remarks sections

Technical Comments:

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1. Please add the physical significance of this study; how engineers can use the results
2. The authors do not provide any finite element model details and do not specify any finite element parameters with specific physical meanings. The authors should provide the finite element model details. The lack of discussion regarding the validation and calibration of the finite element model is enough for this reviewer to recommend the decline of the manuscript until further results and discussions are included.
3. In section 2.2, the authors should add more information regarding the small-scale bridge along with material properties.
4. What is the significance of the using small-scale bridge for the monitoring method? This is not very clear in the text. I recommend adding a few sentences explaining how a small-scale bridge on the other assisted in validating the FE model and monitoring method.

Editorial Comments:

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1. The manuscript needs a thorough review of language and technical writing issues.
2. References’ format needs to be checked.
3. Arrange keywords in alphabetical order
4. Resolution of some figures is low

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors revised the manuscript in accordance with reviewers' comments. They have to check English typos and grammar one more time.

Author Response

I have checked English typos and grammar, and have revised.Please review.

Reviewer 2 Report

- The authors addressed the review comments reasonably well

Author Response

I have revised some English typos and grammar, please review.