Review Reports - Quantification of Microtopography in Natural Ecosystems Using Close-Range Remote Sensing

Round 1

Reviewer 1 Report (New Reviewer)

Dear authors,

The subject is adequate for research and the text is clear and well-written. The manuscript has a very good review of the main close-range remote sensing techniques and their characteristics, addressing limitations and advantages. However, a very important point remains to be addressed, which is the presence of vegetation. How to overcome this problem to properly represent the spatial heterogeneity of the study site? the presence of vegetation may compromise the objective. This should be discussed.

The purpose of quantification for natural ecosystem studies presented as one of the main goals was not achieved. From the literature, provide some metrics and statistics of previous works.

To increase the quality of the manuscript I suggest the inclusion of a discussion section on which some guidelines can be presented (e.g. using TLS, a discussion about the number of scans and their position, for a pre-defined purpose)

Author Response

Author Response to Reviewer 1’s Comments

Comments and suggestions for Author

Dear authors,
The subject is adequate for research and the text is clear and well-written. The manuscript has a very good review of the main close-range remote sensing techniques and their characteristics, addressing limitations and advantages. However, a very important point remains to be addressed, which is the presence of vegetation. How to overcome this problem to properly represent the spatial heterogeneity of the study site? the presence of vegetation may compromise the objective. This should be discussed.

Response:

Thank you so much for your comments. Yes, we agree that the presence of vegetation may compromise the objective. We have polished our explanation on this matter in Section 4.4 and included one additional paragraph in the Discussion section. (see section 6 Page 22)

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2. The purpose of quantification for natural ecosystem studies presented as one of the main goals was not achieved. From the literature, provide some metrics and statistics of previous works.

Response:

Thanks for your comments.

We have included some metrics throughout the literature review in the revised manuscript. In Table 1 we have included the DEM resolution and now included DEM RMSE of each study. In Table 2 (see section 4 Page 11), we added more metrics associated with the use of different close-range remote sensing techniques for collecting microtopography data.

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3. To increase the quality of the manuscript I suggest the inclusion of a discussion section on which some guidelines can be presented (e.g. using TLS, a discussion about the number of scans and their position, for a pre-defined purpose)

Response:

Thanks. We added a paragraph in section 4.4. (see Page 16)

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Reviewer 2 Report (New Reviewer)

I have enjoyed reading the manuscript entitled “Quantification of Microtopography in Natural Ecosystems Using Close-Range Remote Sensing” that was submitted to Remote Sensing. This article provided a systematic framework for micro-topographic studies using close-range remote sensing technologies, and reviewed the application of close-range remote sensing to capture microtopography and develop microtopographic models in natural ecosystems. The authors hold that this article provides one of the most comprehensive and detailed reviews of microtopography data acquisition and quantification for natural ecosystem studies.

There is seldom research has focus on such topic, so the current study is on a topic of relevance and general interest to the readers of the journal. However, based on my personal evaluation, there are some flaws in the structure of this paper. Thus, the authors should clarify some of them and have a major revision for these problems. After that, the results could be further considered. Therefore, I recommend that a major revision is warranted.

Before publication, this manuscript could be further improved by:

1) Revised the section of conclusion. The first paragraph of conclusion used some examples to describe the importance of microtopography on C emissions, which may be not suitable for this section. I think this part could be put in the discussion or other sections.

2) Quality of the figures in this paper needs to be improved, while most of the figures are a bit vague. Besides, if possible, please add the boundaries of the study area for Figure 2, 4, 6, and 8.

3) For section 4.2, I think the authors can add the subheadings for different photogrammetric technique, which make it more layered.

4) As a review paper, the authors should be pay attention to the citation of literature. References need to be added where necessary. For example, Table 2 listed the advantage and disadvantage for different data acquisition method, some necessary literature should be added to support these statements.

5) Especially, the authors have highlighted that microtopography could play a significant role in various ecological, hydrologic, and biogeochemical processes. Besides, these related content were used to introduce the focus of article. In this way, I think a specialized module should be added to describe the impact and application of topography and microtopography for these various processes, such as impacts of topography on surface energy balance (https://doi.org/10.1029/2021MS002862), vegetation photosynthesis (10.1016/j.jhydrol.2022.128833), and so on. Thus, the authors should added some paragraphs to address this problem, which may caused the manuscript more informative. Some references are listed here that maybe useful for the authors to understand the application of topography information in various related research.

L626: “The collection of data can be challenging … … that is often dense.” I think this sentence may be some redundancy.

L670: ”For example, [114] developed a parallel … … of large DEM data”. Please check the reference format for this sentence.

Author Response

Authors Response to Reviewer 2’s Comments

Comments and suggestions for Author

Before publication, this manuscript could be further improved by:

Response:

Thanks for your comments. The first paragraph is now removed from the conclusion and included in the Discussion section (section 6 Page 22).

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2) Quality of the figures in this paper needs to be improved, while most of the figures are a bit vague. Besides, if possible, please add the boundaries of the study area for Figure 2, 4, 6, and 8.

Response:

Thanks! We have now improved the quality of figures and added a boundary to Figure 2, 4 and 6.

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3) For section 4.2, I think the authors can add the subheadings for different photogrammetric technique, which make it more layered.

Response:

Thanks. We have now made two subsections in: one explains about the SfM photogrammetry, and the other describes the development of a fine scale topographic model for microtopographic studies.

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Response:

Many thanks for your comment. We have now included relevant references for each method. (Please see section 4 Pages 11)

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Response:

Thank you for the comments and thanks for sharing relevant references. We have now included a subsection on the impact of microtopography on different ecological processes. Please see section 1.2. and Pages 2-3.

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L626: “The collection of data can be challenging … … that is often dense.” I think this sentence may be some redundancy.

L670: ”For example, [114] developed a parallel … … of large DEM data”. Please check the reference format for this sentence.

Response:

Thanks! As suggested, we have rephrased the sentences and corrected the references style.

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Reviewer 3 Report (New Reviewer)

The article is devoted to the systematic framework for microtopographic studies using close-range remote sensing technologies. I think that the main goal set in the study has been achieved. A large number of bibliographies in this area of science were analyzed - 107 bibliographic sources. Of course, in one article it is impossible to systematize data on all aspects of the study of the microtopographic earth's surface. The authors, in this regard, do not offer any original methods for studying various objects, obtained by themselves. But, probably, for scientists dealing with this issue, it is very convenient to see the achievements in this area of research concentrated in one place.

It seems to me that the authors should have paid a little more attention to the use of remote sensing technologies in the field of exogenous processes in the review. In particular, such a phenomenon as soil erosion. There is a reference in Table 1 to only one process - gully erosion (Brecheisen, Z.S.; Richter, D.D. Gully-erosion estimation and terrain reconstruction using analyzes of microtopographic roughness and LiDAR. Catena 2021).

But the main erosional losses of soil occur due to sheet, rill erosion and ephemeral gully erosion. The magnitude of soil erosion can be measured by the volume of these erosional relief microforms. There are many articles devoted to these studies. In addition, landslides and coastal abrasion are of great danger. The microtopography of the surface of landslide bodies, together with the retreat of the edge of landslide slopes, can also indicate the speed of the process. Many works are also devoted to these aspects of exogenous processes.

Please excuse my english. I hope the meaning of my review is still clear.

Author Response

Authors Response to Reviewer 3’s Comments

Please excuse my english. I hope the meaning of my review is still clear.

Response:

Thank you for your comments. As suggested, we have now included a subsection of the impact of microtopography on different ecological processes including soil erosion. Please see section 1.2. Pages 2-3 for detail. We have also included a few more studies in Table 1 related to exogenous processes (see section 4 Page 11).

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Reviewer 4 Report (New Reviewer)

The problem to be explained needs to be clarified. Relatively difficult to understand, it is necessary to emphasize one of the issues to be studied so that the findings presented are more evident. In this paper, several essential things need to be introduced:

1. Main objective (currently, there are so many objectives)

2. Method of study (content analysis, comparison, interpretation)

3. Results of the synthesis and findings of the study

4. Need to state clear conclusion

Please find the comment enclosed

Comments for author File: Comments.pdf

Author Response

Authors Response to Reviewer 4’s Comments

Comments and suggestions for Author

Main objective (currently, there are so many objectives)
Method of study (content analysis, comparison, interpretation)
Results of the synthesis and findings of the study
Need to state clear conclusion

Please find the comment enclosed

Response:

1. Thanks for your comments. The main objective of this article is to provide a systematic framework for microtopographic studies using close-range remote sensing technologies. To achieve this main objective we focus on addressing four questions, to assist researchers in optimizing the use of these new technologies in support of microtopography-based ecosystem studies. We have revised the Abstract and Introduction section to highlight the main objective of this study.

2. Systematic literature reviews can be classified as domain-based, theory-based, and method based (Paul & Criado, 2020). Our review falls in the category of domain-based review. Out of five types of domain-based review, our review article falls in the category of framework-based review where authors can develop their own framework and use it for structure. Here are the examples of other highly cited review papers which followed their own framework (Maxwell et al., 2018; Mountrakis et al., 2011; Wang et al., 2010; Weiss et al., 2020; Xiao et al., 2019)

3. This is a review article that focuses on providing a “framework” for microtopographic studies using close-range remote sensing techniques. We added more discussion for the synthesis and findings of this study in the Discussion and Conclusion sections (section 6&7).

4. As suggested, we have revised the conclusion. Please see section 7 Page 25

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From examining the manuscript, we noticed the followings:

Comments on terrain attribute: In Table 1, the authors summarize the studies related to microtopography using very high-resolution imagery with a sub-meter spatial resolution (0.1 1 m); however, unfortunately, this study does not convey the reliability of the study, mainly related to the thematic accuracy and geometric precision of the terrain attributes (slope, aspect, flow accumulation, curvature, ruggedness, TPI, TWI, etc.) derived from each case study. It would be good if the study provided information regarding reliability (accuracy and or precision).

Response:

Thanks for your comments. The landforms or microtopographic features are delineated based on terrain attributes. These delineated features then can be assessed for thematic accuracy and positional accuracy. The terrain attributes are derived from the digital elevation model and therefore the accuracy of terrain attributes is dependent on the accuracy of DEM. We have now included the DEM RMSE for each study (in Table 1). Please see section 2 Page 5-7. We also added discussion on the accuracy assessment of microtopography classification in Section 5.3 (see Pages 21-22).

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Comments on the spatial scale: spatial scale is closely related to spatial resolution for thematic maps, such as biomass class, land cover, peat class, vegetation density, etc. The spatial scale is obtained from the spatial resolution (in millimeters) divided by 0.3. In this study, the authors could not highlight the relationship between the spatial resolution and spatial scale of each study reviewed. Readers need to understand the relationship between spatial scale and spatial resolution, as referred to in the research results of how each study converts from resolution to scale. The algorithm is there. "Baltensweiler et al. [56] modeling of soil pH distribution, which stated the most appropriate spatial resolution was found to be 0.5 m, while Stovall et al. [25] found that a DEM resolution of 0.01 to 0.1m was necessary to represent hummocks in a Black Ash wetland system." In this study, the authors also need to highlight the thematic accuracy of each study.

Response:

Thanks. We have further revised our discussion to highlight the relationship between the spatial resolution and spatial scale. Please see section 3, Pages 7-8. We have also mentioned the accuracy reported by both the studies.

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Comments on data acquisition: the choice of method (The study focuses on close-range remote sensing techniques: aerial surveys with Structure from Motion (SfM) photogrammetry, ALS, and TLS.) is too qualitative. The study investigates the qualitatively limiting factors such as time constraints and supporting resources. The author needs to describe how the optimization could be performed and how to combine field survey and remote-sensing methods. The author needs to list the advantages and limitations quantitatively; for instance, the size and number of samples to be measured in the field, or the cost comparison to achieve the minimum accuracy. In other words, this study has yet to provide measurable results regarding the advantages and limitations of each method. Table 2 needs to be more qualitative/descriptive, so it is difficult to get precise conclusions about the advantages and limitations of each method, especially related to geometric accuracy and thematic accuracy.

Response:

Thank you for your comments. We have now revised Table 2 and included metrics in advantages and limitations. We also added information on the number of samples/observations taken in the field. Please see section 4 and section 4.1, Page 11-12.

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In determining microtopography with (1) field surveys; (2) photogrammetry; (3) LIDARs; (4) TLS also does not provide measurable information so that conclusions can be drawn about the capabilities and limitations of each method.

Response:

Thanks for your comments. We have now included more measurable information. Please see Table 2 on Page 11.

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Comments on Delineation of microtopographic sub-chapter: Several delineation methods are focused on three approaches: 1) threshold-based classification, 2) mechanistically based delineation, and 3) machine learning-based delineation; This part does not show measurable results, describing the advantages and limitations of each method in a measurable manner.

Response:

Thanks! These methods are the process to categorize the microtopographic features. The three methods can be applied to a study site to delineate microtopographic features and then the results can be compared quantitatively. We have included a paragraph stating the advantages and limitations of each of these methods. Please see section 5.1.3 Page 19. The authors will attempt this in detail in future studies for more measurable results using specific case studies.

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Comments on the discussion: The author focused more on the "state of the art" method of measuring microtopographic attributes qualitatively; unable to provide a clear picture regarding the capabilities of the data, methods, and results measures that can be produced

Response:

Thanks! As per your comments, we have included the metrics in Table 1, Table 2 and other places where it was needed. We also added more discussion related to these metrics in the revised manuscript. In our future work, we will conduct specific case studies to explore the capabilities of the data, methods, and results related to the use of close-range remote sensing for microtopography studies (please see Conclusion section).

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Comments on conclusions: conclusions made by the authors have not been able to answer straightforwardly and unequivocally the research questions presented above. The conclusion in this article is still unclear. The conclusion must provide information on how to optimize the use of technology in the context of studies related to microtopography-based ecosystems.

Response:

Many thanks for your comments. We have now revised the conclusion section and made it clearer.

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References

Maxwell, A. E., Warner, T. A., & Fang, F. (2018). Implementation of machine-learning classification in remote sensing: an applied review. International Journal of Remote Sensing, 39(9), 2784–2817. https://doi.org/10.1080/01431161.2018.1433343

Mountrakis, G., Im, J., & Ogole, C. (2011). Support vector machines in remote sensing: A review. ISPRS Journal of Photogrammetry and Remote Sensing: Official Publication of the International Society for Photogrammetry and Remote Sensing , 66(3), 247–259. https://doi.org/10.1016/j.isprsjprs.2010.11.001

Paul, J., & Criado, A. R. (2020). The art of writing literature review: What do we know and what do we need to know? International Business Review (Oxford, England), 29(4), 101717. https://doi.org/10.1016/j.ibusrev.2020.101717

Wang, K., Franklin, S. E., Guo, X., & Cattet, M. (2010). Remote sensing of ecology, biodiversity and conservation: a review from the perspective of remote sensing specialists. Sensors , 10(11), 9647–9667. https://doi.org/10.3390/s101109647

Weiss, M., Jacob, F., & Duveiller, G. (2020). Remote sensing for agricultural applications: A meta-review. Remote Sensing of Environment, 236, 111402. https://doi.org/10.1016/j.rse.2019.111402

Xiao, J., Chevallier, F., Gomez, C., Guanter, L., Hicke, J. A., Huete, A. R., Ichii, K., Ni, W., Pang, Y., Rahman, A. F., Sun, G., Yuan, W., Zhang, L., & Zhang, X. (2019). Remote sensing of the terrestrial carbon cycle: A review of advances over 50 years. Remote Sensing of Environment, 233, 111383. https://doi.org/10.1016/j.rse.2019.111383

Round 2

Reviewer 2 Report (New Reviewer)

The citations in the whole manuscript seem to be wrong

Author Response

Thanks for your comments. We checked the references and corrected them as per the Journal's citation style and format.

Reviewer 4 Report (New Reviewer)

This manuscript should be improved (corrected) first, as per the suggestion I gave before. The author needs to increase the conclusion to align with this article's aim.

Author Response

Thanks for your comments. In our future work, we will conduct specific case studies to explore the capabilities of the data, methods, and results related to the use of close-range remote sensing for microtopography studies. We have also revised and increased the conclusion section and made it more coherent with the aim of the article. Please see Section 7, pages 25-26.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Dear authors,
Please find my few comments in the main document. I think this work needs to be improved, especially in the introduction where the objectives are missing. It would also be interesting to present a table of all the advantages and disadvantages of the different approaches highlighted.

Comments for author File: Comments.pdf

Reviewer 2 Report

This manuscript, entitled “Quantifying Microtopography of Forests and Wetlands withRemote Sensing”, is a review paper focused on RS applications for microtopography in wetland and forested environments. The authors begin by defining microtopography and connecting it to important biogeochemical processes. They then write that there have been other review papers examining forests and wetland remote sensing, but none focusing on microtopography.

As a reviewer, the essential question I am struggling with for this manuscript is whether or not it makes enough of a contribution to warrant publication. Section 2 begins with a review of sUAS and regulations for conducting flight operations within the United States. It then goes through a brief introduction to flight planning, GCPs, and structure from motion before introducing a number of equations regarding blurring and GSD. None of this is new information. Table 1 is a collection of papers that included some element of microtopography.

From lines 193-194: “The studies are not directly related to microtopography but they did use high-resolution DEM which is the primary requirement of microtopography-based studies”

It is unclear what the contribution is here.

Section 2 closes with a paragraph on the advantages of sUAS operations over field-based work in terms of increased coverage, and then share some of the different software packages currently available for structure from motion processing. Again, there is really nothing new or interesting here.

Sections 3,4, and 5 are similar- opening with definitions, already available in other reviews or manuscripts, some collected papers and/or examples, but it is unclear what the reader is gaining from these studies being brought together. Many different authors have published papers that involve some aspect of microtopography, but listing them is not enough to warrant publication as a review paper.

Section 6, Discussion, opens with a very specific sentence on lidar and then mentions field data and using RTK GPS to improve location accuracy. This is confusing and seems out of place.

Section 6.1 Challenges… doesn’t introduce any new information that is not available elsewhere.

Section 6.2 Future Directions is the most promising section, but opens in a confusing way: “The scale of the microtopographic features of interest is an important consideration.” This idea is a central component of studies involving microtopography, but isn’t adding anything to the overall discussion.

The references are pertinent and appropriate, but the manuscript reads more like a collection of isolated facts from papers that happen to deal with high resolution DEMs than a coherent study synthesizing the current state of knowledge about microtopography and identifying data gaps and important paths forward.

I don’t think the authors have made enough of a case for publication. It is unclear what significant contribution this paper makes.