Efficacious GPR Implementations of Z-Transform-Based Hybrid LOD-FDTD with Subgridding Scheme: Theoretical Formalism and Numerical Study

Round 1

Reviewer 1 Report

The author presents a hybrid subgridding LOD-FDTD method for 3D GPR simulation. The key point of this manuscript is solving the contradiction of the accuracy and efficiency of traditional FDTD method. However, the author only individually conducted three GPR scenarios to verify the correctness and efficiency of the proposed method, there is no comparisons with other existed methods. Methods such as finite element time domain (FETD) and rotated staggered grid (RSG) have been implemented widely in the GPR forward simulation under background with characteristics of non-uniform, dispersion, and anisotropy. Moreover, subgridding FDTD has also been investigated in literatures, such as the content below:

[X. Y. Zhang, L. N. Yin, R. L. Chen and B. P. Ren, "Subgridding FDTD Modeling of Ground Penetrating Radar Applied with Unconditionally Stable Algorithm," 2021 13th International Symposium on Antennas, Propagation and EM Theory (ISAPE), 2021, pp. 1-3, doi: 10.1109/ISAPE54070.2021.9753475.]

Therefore, author should include comparisons on the merits such as interfacing error, execution time and memory cost to outstand the proposed method.

Other weaknesses:

1. As the manuscript proposed a method based on Z-transform, and Z-transform can save memory efficiently. Author mentioned that Z-transform does not have to preserve values from former moment, however, there is no relevant information about the reason. Author should further explain why Z-transform is more efficient before the method equation explanation part, since Z-transform is a key point of the manuscript.

2. In Figure. 10, there is little difference between the error of two ratios of grid generation. Author should explain the reason why no big difference in multiple target scenario while large difference in the single target scenario.

3. The dispersive sphere simulation should be the Section 3. C, author should carefully check the errors in the structure of the manuscript.

4. The information of overall cell number in the simulation examples is missing, which is a critical index regarding the performance of the proposed method.

5. The manuscript contains a lot of linguistic, grammatical and orthographical errors. Careful proofreading, preferably by a native speaker. The quality of figure needs also be proved significantly.

Author Response

Dear Reviewer,

    Thank you so much for your valuable comments, please see the attachments.

Wish you all the best!

Author Response File: Author Response.doc

Reviewer 2 Report

This paper describes the simulation of GPR in soil.

This reviewer did not see too much innovation in this paper. In addition, the simulation is not validated by experiments.

the purpose of this paper is quite vague.

 

Author Response

Dear Reviewer,

    Thank you so much for your valuable comments, please see the attachments.

Wish you all the best!

Author Response File: Author Response.docx

Reviewer 3 Report

Your paper provides a nice stepping stone for readers who have an interest in using FDTD for GPR computer simulations. The presentation is clear, the models were adequately described and the results shown look acceptable. There were a number of locations where I made suggestions to make the English more readable.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

    Thank you so much for your valuable comments, please see the attachments.

Wish you all the best!

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have done a conscientious and thorough job of addressing the reviews. It is suggested to consider the publication of the manuscript.

Author Response

We very sincerely thanks the comments from the reviewer, it makes our work become higher quality. 

Reviewer 2 Report

The authors are encouraged to develop more things, then publish them together. The current paper is short of innovations or validations. Anyway, if the editor agrees that this paper can be published, I can differ my opinion aligning with the editor. But it is better to have a third reviewer.

Author Response

We here sincerely thank and cherish the comments from the reviewer, it makes our paper become higher quality.