An Improved Approach for Generating Digital Twins of Cultural Spaces through the Integration of Photogrammetry and Laser Scanning Technologies

Round 1

Reviewer 1 Report

The authors undertake a novel strategy to integrate the strengths of two optical data collection technologies to capture digital records of historical mansions in the Kifissia area for cultural preservation. The intention to replicate the mansions as digital twins is intended to preserve architecturally important artifacts for cultural tours, historical archival and educational purposes. The article reports on data collection strategies such as working in partial cloud cover to avoid shadows, utilizing several image platforms (cameras, laser scanning, drone photography) and subsequent photogrammetric measurements to align, register and integrate data collected from all sources.

A few comments are offered here as suggestions to improve the article’s description of the data collection process:

In Figure 2, it is hard to see the manually inserted control points that are quite small and not clearly labelled in the Figure. If the purpose of the Figure is to demonstrate where such points are located, the authors should make them more prominent and easier to identify in the Figure.

In Figure 5, I suggest showing a photographic image of the mansion roof to allow readers to visually compare the two versions.

I was curious to read that when some architectural features were obstructed by vegetation or other barriers, or damaged, that similar features (e.g., railings, cornices) were copied and pasted from other parts of the mansions. This would produce an image that is implicitly more complete but certainly not an explicit digital twin. I wonder if such areas in the digital version were symbolized somehow to acknowledge this, since it corrupts the principle of producing the most comprehensive and precise replica of the mansion(s). Yet the authors do not discuss this apparent prioritization of one goal (completeness) over the other (precise replication). A quantification of the percentage of imagery that is in fact an exact replica relative to the imagery that is revised somehow would strengthen the authors’ methodology considerably, without mandating a return to collect more data. Lacking a report on how much of the digital twin is in fact not an actual twin leaves the paper and its concluding section hyperbolic, since the authors conclude (ironically) that their integration methods solve the problem of digital twin capture completely.

Author Response

Firstly, we would like to thank you for your effort in revising our manuscript titled “An Improved Approach for Generating Digital Twins of Cultural Spaces Through the Integration of Photogrammetry and Laser Scanning Technologies”. 

We really appreciate the careful review and constructive suggestions. In what follows, we try to address all the points raised in the review. It is our belief that the manuscript is now substantially improved after making the suggested edits, as shown in the attached PDF.

Author Response File: Author Response.pdf

Reviewer 2 Report

Suggested articles to enhance photogrammetry and laser scanning in processing data for critical calculations.

Author Response

Firstly, we would like to thank you for your effort in revising our manuscript titled “An Improved Approach for Generating Digital Twins of Cultural Spaces Through the Integration of Photogrammetry and Laser Scanning Technologies”. 

We really appreciate the careful review and constructive suggestions. In what follows, we try to address all the points raised in the review. It is our belief that the manuscript is now substantially improved after making the suggested edits, as shown in the attached PDF.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript deals with the issue of creating digital twins. The topic is topical and combines the use of two technologies photogrammetry and LST.

Comments:

The abstract needs to be revised. It is too general. It should contain, among other things, the methods used and, in part, the results obtained. 

It would be useful to distinguish the aim of the paper and the research from the aim of the project described in the paper (Row 151). The description of the project should then be included in a different part of the article than the Materials and Methods section.

A location (map) of the study area with a brief description, and photos, would also be helpful.

The locations of the scanner and cameras were positionally located - i.e., were their locations targeted using GPS? If so, with what accuracy, coordinate system, etc.

The Materials and Methods chapter should be supplemented with a technical section, a description of the actual methods used - both geodetic data collection and focusing on accuracy calculations. 

What were the parameters of the data collection equipment used? On line 181 the source "smartphones" is mentioned, what type in what quality, etc...?

What were the scanning parameters? E.g. number of points, accuracy

Adding accuracy characteristics and comparisons to the results would have been useful. In this section, I am missing e.g. sections through the created models and a comparison of the methods used.

Row 336 has the text "its exceptional precision", on what basis did you arrive at such an assessment?

Author Response

Firstly, we would like to thank you for your effort in revising our manuscript titled “An Improved Approach for Generating Digital Twins of Cultural Spaces Through the Integration of Photogrammetry and Laser Scanning Technologies”. 

We really appreciate the careful review and constructive suggestions. In what follows, we try to address all the points raised in the review. It is our belief that the manuscript is now substantially improved after making the suggested edits, as shown in the attached PDF.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

I thank the authors for responding to my review and completing the manuscript.