Three-Dimensional Reconstruction and Geometric Morphology Analysis of Lunar Small Craters within the Patrol Range of the Yutu-2 Rover

Round 1

Reviewer 1 Report

The three-dimensional and geometric morphology analysis method for impact craters based on stereoscopic images captured by navigation cameras is proposed based on the metre-scale craters around the movement path of the Yutu-2 lunar rover. Crater is an important feature of lunar surface topography. This method is of great significance for the selection of landing sites for lunar probes and the research of lunar geological history and evolution. The main innovation of this method is the CscaNet stereo matching algorithm. Based on the proposed method, the 3D model of the crater is reconstructed and the topography of the crater is researched in detail. The method is different from the traditional two-dimensional extraction and analysis of impact craters, and has great innovation. The method section is introduced in detail. KITTI 2015 data set and real lunar data are used to validate the proposed algorithm. The experimental verification is sufficient. However, there are still the following problems in this paper that need to be modified.

 1.         Abstract content needs to be simplified. There is no need to label references in abstracts.

2.         Explain the meanings of the different color boxes in Figure 1.

3.         Figure 18 is not shown.

4.         Conclusions content needs to be simplified.

Comments for author File: Comments.docx

Author Response

    Thank you for your letter and for the reviewers’comments concerning our original manuscript entitled “Three-dimensional reconstruction and Geometric Morphology Analysis of Metre-scale Craters within the Patrol Range of the Yutu-2 Rover” (ID: remotesensing-2495275). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked the “redline” comparison feature in the paper.
    It is noted that our paper has been re-modified according to your comments in content and form. We hope that the correction will meet with approval.

    Once again, thank you for your comment and approving my work!

Author Response File: Author Response.docx

Reviewer 2 Report

This article presents a 3D reconstruction method for small lunar craters and an application to the search for invariants in the geometry of these small craters. the problem is clearly set out, in particular the fact that the usual methods are not suitable for very small craters. Both parts of the study are relevant and based on a clearly presented state of the art. 

These two parts are very different, but since they are presented in the same paper, it would be preferable that they be more closely connected. This is the main weakness of this paper. For example, in the study of correlations between geometric parameters, the scattering of values is supposed to be due to the diversity of shapes, but what is the influence of measurement error, which was precisely addressed in the first part? With what confidence are the depth and diameter parameters estimated? And what models are they based on? For the diameter estimate, the equal-area circle is considered, which is a kind of modelling. But how is depth estimated? Is it the depth of an analytical model ? If it is the mere difference between the points of extreme elevations, then given the measurement noise, there is no doubt an overestimation of the depth, which could distort the statistical laws.

The presentation should be clarified :

- the fact that the craters are on the moon is not obvious before reading the article, this should be said in the title and at the beginning of the abstract ;

- at the end of the introduction, it is too early to announce the performance achieved (lines 150 and 159);

- in section 3, lines 374, 403, 407, 416, 428, 449, these numberings, which are not formally sub-sections, make the structure of the section very confusing ;

- the description of the method (section 3) is very complete, however, it would be useful to indicate more clearly which are the input and the output of each processing step in each sub-section.

Comments about illustrations :

- all figures : increase letter size

- figure 13 and 14, names on the left margin : write normally and rotate the word

- figure 19 : histograms would be more meaningful to show tha statistical distribution (in coherence with table 7)

Other minor comments :

line 177 : small field of view or small focal length ?

lines 275 and  281 : writing 1/2H or 1/4H is ambiguous. I guess 1/2H means (1/2)H, in this case write (H/2)x(W/2)x32.

line 277 "three, 16, three" : choose between numbers and words

line 381 : "kernel size d" but d is already used for depth.

 

 

Author Response

    Thank you for your letter and for the reviewers’comments concerning our original manuscript entitled “Three-dimensional reconstruction and Geometric Morphology Analysis of Metre-scale Craters within the Patrol Range of the Yutu-2 Rover” (ID: remotesensing-2495275). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked the “redline” comparison feature in the paper.
    It is noted that our paper has been re-modified according to your comments in content and form. We hope that the correction will meet with approval.

    Once again, thank you for your comment and approving my work!

Author Response File: Author Response.docx

Reviewer 3 Report

This research study introduces a method for 3Dmodel extraction and analysis of impact craters based on stereoscopic images captured by navigation cameras of Yutu-2 lunar rover. Although in this work, the 3D modelling process and the analysis is well explained, some major technical concerns are remained, that need to be addressed in the next revision.

 Technical considerations:

1-   The paper is well structured. However, the mythology section is hard to understand for reader. Since you use different cameras (the front and rear camera and stereo cameras), it is not completely clarified which part of the proposed method uses which camera data. So, the authors need to revise the flowchart and clarify exactly which data is used in the process. (add Input data to your flowchart)

 2- The abstract should be revised and summarized to explain the important findings of the research. The formula used in the Abstract Section should be omitted.

 3- The Introduction Section of the manuscript explains the related papers and challenges. However, for the reader with no background in Astronomy, the importance of lunar impact craters reconstruction and its contributions to the scientific community is not clear. So the authors need to clarify this in the introduction Section.

 4-  The quality of Figure 2 is not good. The camera locations are not clear because the image quality is relatively low. Similarly, Figure 3 is a good one.

5- In Lines 214-215, what are the specifications of cameras in Yutu-2 lunar rover? And what are the parameters of the cameras in the pre-calibration process? Did they change a lot after your self-calibration process?

 6- The process of self-calibration in Section 2.1 is not clear and these questions remained unanswered to the reader.  What kind of software did you use? How did you apply the solar panels lines as image targets? What was the accuracy of your targets in image space? How many images did you use for self-calibration?

7- In Section 2.1, how did you solve the problem of correlations between interior parameters? As you just use images with no rotations, there might be high correlations between the estimated parameters. How did you check the accuracy of estimated parameters?

 8- In Section 2.2, how was the quality of matching with SURF algorithm? The authors require to add some sample images clarifying the visual quality of matching process.

 9- In Section 2.2, did you use the stereo images for the computation of visual positioning of the lunar rover? If yes, how did you solve the problem of low quality of the matching process? Using the CscaNet??

 10- In Lines 262-264, it is not explained how you have calculated the positioning accuracy. What was the accuracy of telemetry data which you have utilized?

11- In Figure 9, the process you have applied to calculate the precision of the 3D coordinates is not clear. How did you calculate the figure numbers? Did you use the well-known (Base/Height) formula?

12- In Section 3, the authors must add some explanations clarifying the analysis they have done. At first, you have some analysis on the matching results, then some analysis of Metric Features of Impact Craters and finally the Geometrical Morphology Analysis of Impact Craters. The authors must clarify the reason of each analysis, the evaluation metrics used and comparing datasets\algorithms (if applicable!).

 13- In Section 3.2, Lines 577-578, how did you analyse the accuracy of your results? How did you compute 0.98 cm value? It is not explained in the manuscript.

14- A Discussion Section must be added to manuscript addressing the basic findings\results. The contents of this section should be separated from the Conclusion.

Editorial considerations:

The manuscript needs to be reviewed for some grammatical and spelling mistakes.

  Minor considerations:

1-      The manuscript should be checked regarding the section numbering order. Page14 you have two subsections with same numbering.

2-      Caption for Figure 19 should be revised. What are the (a), (b) … graphs show?

3- The format of References should be revised according to the journal’s style.

The manuscript needs to be reviewed for some grammatical and spelling mistakes.

Author Response

    Thank you for your letter and for the reviewers’comments concerning our original manuscript entitled “Three-dimensional reconstruction and Geometric Morphology Analysis of Metre-scale Craters within the Patrol Range of the Yutu-2 Rover” (ID: remotesensing-2495275). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked the “redline” comparison feature in the paper.
    It is noted that our paper has been re-modified according to your comments in content and form. We hope that the correction will meet with approval.

    Once again, thank you for your comment and approving my work!

 

Author Response File: Author Response.docx