Integration of Non-Destructive Acoustic Imaging Investigation with Photogrammetric and Morphological Analysis to Study the “Graecia Vetus” in the Chigi Palace of Ariccia

Round 1

Reviewer 1 Report

The authors present a data fusion technique involving several non-contact inspection techniques for the condition assessment of a piece of art, mural painting Graecia Vetus. The considered techniques comprise photogrammetry, acoustic imaging, and acoustic tomography. The data fusion approach consists of a supervision of the images obtained through the previous techniques, after applying certain threshold filtering to highlight the presence of anomalies possibly due to damage. While the use of these techniques is not novel, and the data fusion approach may be simplistic, this work provides a nice example of the integration of several non-destructive non-contact inspection techniques for the analysis of artistic heritage pieces. The manuscript is nicely written, and the ideas are presented in a compelling manner. Therefore, this reviewer recommends the publication of this work after minor revision. I only have some minor remarks the authors may find useful to enhance the quality of the manuscript.

Remark 1. Eq. (2) consider adding other references different from [7,8] (by some of the authors) giving the theoretical basis of the formulation. In addition, consider changing term “higher order terms” for an alternative more mathematically formal term.

Remark 2. Revise equations and write operators using Roman Style. For instance: “IFFT”, “ln”, etc.

Remark 3. Eq. (4), consider adding the differential “df” after the squared norm of the transfer function H_i(f).

Remark 4. In the photogrammetric survey, how many pictures were used in the geometrical reconstruction?

Remark 5. Define the term “\Delta f_n” in the integral in Eq. (6).

Remark 7. Eq. (9), term “RVPV” is what the authors refer to as the “relative variation of pulse velocity”? If so, please describe here.

Remark 8. Section 3.2. The authors refer to some visible cracks, although I cannot see them from the provided graphical information. Can the authors remark them in e.g. Fig. 10?

Remark 9. Section 3.2, line 412. Can the authors clarify how they computed the “best obtainable uncertainty?

Remark 10. Fig. 11, how did the authors compute the wall depth in the figure on the top right?

Author Response

The authors wish to thank the Reviewers for helping to improve the manuscript. According to the Reviewers’ comments, the authors propose their revisions and the answers to each remark. The lines specified for the integrations refer to the first draft of the manuscript.

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors in this paper investigated a novel sensing method for evaluating the health condition of a mural painting using a integration of photogrammetry-based methods with acoustic imaging methods. Overall, the paper is well drafted. The reviewer has a few comments attached which may be helpful to improve the quality of the paper.

1.       Page 2, Line 61. The authors discussed some of the benefits for integrating two technologies together. However, the reviewer likes to see an expansion on the discussion. In the reviewer’s view the novelty (contribution) of this study lies in the integration of two types of sensing data (i.e., digital images vs. sound waves) rather than 2D vs. 3D data (because ultimately, 3D photogrammetry data is shown as 2D results as well). There are a few studies in civil infrastructure inspection using multiple sensor technology for inspecting bridge decks (see the link below for one example). Adding some perspectives from it to this paper would strengthen the quality of this study. There are also some challenges in fashioning data from different resources. The authors may want to dig into this aspect and claim the contribution accordingly.

https://www.researchgate.net/profile/Ralf-Arndt/publication/236146064_Comparison_of_NDT_Methods_for_Assessment_of_a_Concrete_Bridge_Deck/links/568a9db008ae051f9afa622a/Comparison-of-NDT-Methods-for-Assessment-of-a-Concrete-Bridge-Deck.pdf

2.       The reviewer has a few comments about the viability of this proposed method. Is there any reason that the authors select the ROI from the building? Is this because the ROI suitable for verification of the method; or because the ROI is culturally valuable? Or other reasons? Does the proposed method work well for other situations (e.g., outdoor, uncontrolled environment)?

3.       A major concern from the reviewer is about the rationales for damage detection in Table 1. For the photogrammetry-based features (detached; cracking), these are the possible assumptions without ground truth data. As the detecting results is highly related with the cut off threshold, the fidelity of damage detection hence would be questioned.

 

4.       Although the result in Fig. 13 shows integration from multiple perspectives, it is still unclear to the reviewer that how does this integrated results could be superior to individual maps. Does the owner feel easier to understand the health status with the new approach? What if the results from different dataset are conflict with each other? Again, visiting some existing work in NDT of bridge deck or other similar work in civil infrastructure inspection using multiple sensing technologies would be beneficial, can strengthen the discussion of this paper.

Author Response

The authors wish to thank the Reviewers for helping to improve the manuscript. According to the Reviewers’ comments, the authors propose their revisions and the answers to each remark. The lines specified for the integrations refer to the first draft of the manuscript.

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have addressed the reivewer's comments hence I recommend this manuscript to the journal.