Building an Indoor Digital Twin—A Use-Case for a Hospital Digital Twin to Analyze COVID-19 Transmission

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is a very interesting study offering a new module to IndoorGML. The case study is indeed very valuable and should be considered for further inclusion in the OGC standard IndoorGML. 

However, the presentation of the work will benefit if more motivations and elaborations are provided. I also believe some of the taken decisions should be reconsidered. 

- the motivation for using IndoorGML should be strengthened. CityGML and IFC can be used more succesuly for the same purpose.

- The requirements for the extension of IndoorGML are very brief. It should be thoroughly discussed how they are derived and why they are  translated to the IndoorGML requirements for extension as given in Table 1. For example, why a 2D map should be maintained together with 3D map? A 2D can be derived from a 3D map once available.  

- Why LODs are created? How they relate to the specified Infection models?

- The same question for PoI. What do they aim to represent? Why is the reason they are included in the H-module? Isn't it possible to use the mechanism of creating additional thematic layers? PoI are points and in general can be derived from the geometry of specases or features. Maintaining them as classes in the module can lead to duplicates and errors.  Related to this is Figure 7, where the IndoorElelment is aggregation of PoI anD Facility. What if users got different ideas about what PoI and what Facility should be in the context of COVID?

- Elaborate on the role of PoI and Facility. Doe Facility includes furniture? If not how the Furniture is classified? IndoorGML is a space model. Generally, all features are considered spaces. Please motivate why PoI will not be in conflict with the space concept. 

    - Figure 8. I don't see the need to extend IndoorGML by a top classes. H-model should provide a specialisation of the core model and not aggregation? Such approach is methodically incorrect. 

- What are the new attributes that are included in the extended IndoorH? 

I have quite many comments on the implementation.

- How the model is implemented? Is the use case building organised in one IndoorGML file? Provide some details on the actual implementation of the p- oroposed model: i.e. LOD, PoI, Facilities. 

   - I wonder what the place is of the hash grid in IndoorH (Figure 12). theoretically such dense network mean that the indoor room spaces have to be subdivided into sub-spaces. Having only a network without spaces (primal spaces) is not allowed in IndoorGML 1.1. It was made possible only in IndoorGML 2.0. Please clarify the role and place in the model. 

 - Apparently the hash networks is created for smooth movement of agents. But this is not mentioned as a requirement. PLease re-consider and explain.  

- the authors mention Navigable cells on page 15. This means that Navigation module is also needed. However this is not elaborated in the paper. Please includ eteh navigation model in IndoorH. 

- The use of IndoorH with the  infections models (section 7) doesn't illustrate which components of IndoorH are used. It certainly doesn't portray ho wthe extension with LOD, PoI and Facility makes specific analysis easier. In this respect I would recommend identifying specific queries or analysis prior providing visualisations. Even if it is only for visualisation it shudl eb clear what is supposed to be observed.

 - Please elaborate what from the IndoorH has been imported in CFD for simulation. Figure 15 and 16 gives the impression that only spaces are used. Then the logical question why extension is used?

 - The functionality of InCOVID is not specified. In this respect the comparison provided in Table 5 cannot be judged. Furthermore, it is not justified how the infection models are supported by the IndoorH (see also comments above)  

The authors should clearly specify that they are using IndoorGML 1.1 and not IndoorGML2.0.

 I hope the above remarks help. Success with the revisions!   

Comments on the Quality of English Language

not bad. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this paper, authors propose the framework of indoor hospital digital twin for COVID-19 transmission and spatial development analysis. The self-content modeling and simulation are somehow well grounded. The main problem lies in the scientific contributions as a research article since authors try to focus on airborne virus exposure. Authors need to carefully address the following issues.

1. What is the key typical feature for the studied COVID-19, compared to other airborne or particle-adhering virus? What is the academic value or reference values on indoor air quality control in general? Benchmark comparison and validation or measurement are of high necessity to ground this soft-ware concentrated simulation, since there have been available detailed fluid dynamic or public health research works on Covid-19.

2. Authors resort to a rather problematic framework view to investigate the hospital indoor environment control, especially with emphasis on digital twin techs. While the modeling study runs the risk of reducing the necessity of how such OGC indoorGWL work to certain results, with respect to ordinary modeling approaches.

3. The sections on transmission and infection models show limited awareness of alternative Covid-19 features or pivotal thermal-physical properties and limited rigor in integration detailed P to P/S/A relationships. Authors seems to express general airborne virus indoor distribution regulations, rather than concentrating on differentiated Covid-19 procedurs including partition, convection, decay etc.

4. It is not quite clear how construction level, source emissions, indoor materials, indoor ventilation and hospital building conditions are quantitatively linked with the concerned transmission process.

5. Benchmark or baseline comparisons are of high importance with global research views. Authors validate and compare with InCOVID+ system for software simulation. Moreover, please clarify the key advance and progress over available similar indoor air quality tools, particularly for the so-called digital twin. 

6. The present form is more like a region case related advocating report or methodology proposal, rather than an academic article with significant scientific novelty. Authors should reconsider and restructure the conclusions with emphasis on the novelty an application value.

7. What are the main implications of the study's findings for COVID-19 prevention and control, as well as strategies for respiratory disease prevention? How can the research findings be translated into practical recommendations for improving hospital indoor air quality and reducing transmission risk in real-world settings?

 

Comments on the Quality of English Language

Moderate editing of English language required.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors present a framework for developing indoor digital twins grounded in a use-case study for hospital. This framework is built upon OGC IndoorGML, which acts as a standard for the indoor data model and the encoding method for indoor spatial information. The research topic is vital, and the research approach effectively supports the findings. Therefore, I have decided to accept it with minor revisions for publication in the “ISPRS International Journal of Geo-Information.”

 

Here are my comments on improving the manuscript:

- The abstract section is clear. However, it should include research limitations. Please kindly update the manuscript.

- Before stating the potential contributions in the introduction section, please clearly deliver the research questions and objectives to enhance clarity in the introduction. Kindly update the manuscript accordingly.

- Clarifying the validation section would be beneficial if the authors added a new evaluation figure. Additionally, a survey with industry experts should be considered to validate the proposed framework.

- To strengthen the conclusion, the authors should clearly outline the research limitations and actively emphasize the potential for future work. This addition would enhance the overall impact of the study.

- There are typos (e.g. line 449 in page 15, etc.) in manuscript. Please check whole manuscript carefully and update.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I don't have more comments. The authors reflected thoroughly all my comments 

Comments on the Quality of English Language

The paper needs to be checked by a native English speaker 

Reviewer 2 Report

Comments and Suggestions for Authors

Authors have addressed review issues rationally.

Comments on the Quality of English Language

Minor editing of English language required.