Unmanned Aerial Vehicle-Based Structure from Motion Technique for Precise Snow Depth Retrieval—Implication for Optimal Ground Control Point Deployment Strategy

Round 1

Reviewer 1 Report

In general is the structure of the paper suitable. But the style of methodology presentation is too complicated. It is clear what the authors want to prove, but the methods are not entirely clear. Methods must be described more clearly (e. g. difference between Strategy A vs. Strategy B). It is also necessary to describe reasons for choosing used study area (relatively flat urban area).

It is necessary to add more references to the discussion and compare findings with other authors from similar studies.

 

Author Response

We would like to thank the reviewer's comments and suggestions that help a lot to improve the quality of this work. Please see the attached PDF for our item by item responses to reviewer's comment.

Author Response File: Author Response.pdf

Reviewer 2 Report

 Summary:

   Comments and Suggestions:

- Please avoid the use of abbreviations in the title of the paper.

  - The abstract is too long and contains many abbreviations.  

- The introduction should be divided into two sections: introduction and related works.  

- The authors need to add a short paragraph at the end of the introduction which describes the structure of the paper.  

- In addition, the authors may insert a figure which illustrates graphically the structure of the paper too.  

- The related works may be summarized in tabular form in order to emphasize the limitations of existing approaches and the originality of the proposed approach.  

- The authors need to add a short paragraph about the security aspects of drone communications. May this influence the proposed approach?  

 For this purpose, they may include the following references (and others) in their study:  

 1. https://ieeexplore.ieee.org/document/9842403    2. https://www.mdpi.com/1424-8220/21/6/2057  

- Line 113: " snow depth [24,31,32,34]. " ===> Please avoid the use of many references in this manner without providing details about them.

  - Line 146: " We used a DJI Phantom 4 quadcopter UAV to collect photos
" ===> Please provide more arguments about the choice of this specific type of UAVs. 

- Figure 1: Photos were taken in 2021. Why not consider more recent photos?   

  - Some sections are too long and dense which makes them difficult to read and understand. (e.g., Section 5)   - For this reason, it is better to split them into subsections with appropriate titles.   

- Figures are not clear enough which makes them difficult to understand too.  

- The content of Table 1 is not clear enough.  

- Line 266: " measured by the Pearson correlation coefficient" ===> please provide more details about this entity.  

- Section 4.1 is difficult to read and understand. Please simplify it and make it more accessible for readers.  

- It is a bit strange that no mathematical equations or algorithms were presented in the paper.  

- Is it possible to share the collected data?   

- The authors need to identify the limitations of their approach and propose more future work directions.     

Author Response

We would like to thank the reviewer's comments and suggestions that help  improve the quality of this work. Please see the attached PDF for our item by item responses to reviewer's comment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper demonstrated that the GCP deployment strategy is important to snow depth estimates with SFM Technique. The study area is small, and snow depth only varies from 5 to 30 cm. In future work, it’s better to conduct a wide area filed campaign and get a large snow depth range. Specific comments are as follows:

 

 

1. P1, line 44: “rapid decreasing trend in recent decades at a global scale in terms of snow depth…”, This conclusion is applicable to North America, not global. Please correct it.

2. P2, lines 70 and 72: full name of Unmanned Aerial Vehicle occurs two times, the second abbreviation is OK.

3. Different strategies were used in this manuscript, please clarify the basic principles.

4. P7, line 254, road maybe was covered by snow unless cleared out artificially.

5. P7, lines 268-275, these explanations are unnecessary, I think.

6. Fig.4 showed SfM-based snow depth retrievals have a big change for Low-Accuracy sets of GCPs, so whether the classes of High- and Low-Accuracy sets are correct or not？

 

7. Section 5 (Discussions) should be divided into several subsections.

Author Response

We would like to thank the reviewer's comments and suggestions that help a lot to improve the quality of this work. Please see the attached PDF for our item by item responses to reviewer's comment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors considerted all my comments and suggestions. Good luck.