Adapting the High-Resolution PlanetScope Biomass Model to Low-Resolution VIIRS Imagery Using Spectral Harmonization: A Case of Grassland Monitoring in Mongolia

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript by Jargalsaikhan et al. presents a methodology for adapting a grassland biomass estimation model from high-resolution PlanetScope imagery to low-resolution VIIRS imagery through spectral harmonization using the classified SBAF technique. The description of the experiment implementation is detaily and the topic is relevant and interesting for the remote sensing community. However, the writing structure, expression, the manuscript arrangement, the logic/merit/novelty in the abstract etc. needs substantial revisions. Please see my specific comments below.

Major comments

1. The authors stressed that they try to monitor Mongolia grasslands, but they did not demonstrate the importance of such monitoring. Maybe, just for reference, the authors may revise the title as “Adapting High-Resolution PlanetScope Biomass Model to Low-Resolution VIIRS Imagery Using Spectral Harmonization, A Case of Grassland Monitoring in Mongolia”. This title may attract more readers of this topic rather than confined your study into a specific region. Otherwise, readers may wonder will your method still hold true if applying your method in another place/vegetation type?
2. In the abstract, I suggest the authors pointing out the deficiencies/shortcomings of the current research directly. This is the cornerstone of your study. What is the merit/novelty of your study? I noticed that the authors have demonstrated this point of view in the introduction part. Nevertheless, the authors did not articulate this point in their abstract.
3. I suggest the authors simplify the data and methodology part. This section accounted for a large proportion of the whole manuscript. Maybe the authors can move some content into the Appendix. Please simplify the methods that are not proposed by the authors, which can be achieved by properly citations. For example, is it necessary to show the NDVI calculation equation? Moreover, the overlength data and methodology section makes the manuscript looks like a report rather than a scientific paper. Please only describe the necessary processes.
4. The results section needs substantial revisions. The results section typically only shows “what you got in your experiment”, rather than provides information on “how to do it”. Information about “how to do it” should be properly put in the data and methodology section.
5. The expression in the results section makes the manuscript looks like a report, e.g., Lines 400-403

Minor comments

Line 17 Why low-resolution imagery provides broader coverage than high-resolution imagery? Both of them can depict a global-scale coverage. Please clarify.

Line 18 What is the relationship between “parameter estimation” and “insufficient ground reference data”? Do you mean the parameters are retrieved from ground reference data, validating the parameters using the ground reference data? Please clarify the logic.

Line 105 Please provide a brief description of the manuscript arrangement before the methodology section.

Fig. 8 This figure is supposed to appear in the data and methodology part. Again, this writing structure/style makes the manuscript looks like a report rather than a scientific paper.

Table 2 A plot, e.g., a bar chart, may provide intuitive vision for the readers.

Comments on the Quality of English Language

No comments.

Author Response

Dear Reviewer 1,

Thank you for your thorough and insightful feedback on my manuscript. I am uploading a revised version of the manuscript along with a detailed response to your comments. In the revised manuscript, I have addressed all your suggestions to enhance clarity, structure, and scientific rigor. Key updates include adopting your suggested title, "Adapting High-Resolution PlanetScope Biomass Model to Low-Resolution VIIRS Imagery Using Spectral Harmonization: A Case of Grassland Monitoring in Mongolia," to emphasize methodological innovation and broader applicability; restructuring and simplifying the Methodology section with clear subsections; and revising the Results section to focus solely on outcomes. Additionally, I have incorporated uncertainty analysis (e.g., RMSE of 11.6 g/m², R² of 0.92, mean percentage difference of 10.74%) into the Abstract, Discussion, and Conclusion to further strengthen the study’s robustness, as detailed in the response document.

Figures and tables (e.g., removal of Figure 8, splitting Table 2) have been adjusted per your guidance, and the English has been refined throughout for improved readability. I believe these revisions significantly enhance the manuscript’s quality and align with your recommendations. Please let me know if further clarifications or adjustments are needed. I deeply appreciate your time, expertise, and constructive comments, which have greatly improved this work.

Sincerely,

Mr. Margad-Erdene Jargalsaikhan

Corresponding Author

PhD Student

Yamaguchi University, Japan

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The study titled “Adapting High-Resolution PlanetScope Biomass Model to Low-Resolution VIIRS Imagery Using Spectral Harmonization for Grassland Monitoring in Mongolia” studies an interesting subject. There are a few concerns regarding the objective and novelty, structure, literature review, and evaluation of the results that I listed below, followed by some minor points:

• Main objective: The main objective of this study is confusing for me. Is it to develop and/or advance harmonization algorithm to map biomass or both? If the ultimate objective is biomass mapping, the authors should justify choosing this approach. For example, why adopt a model from PlanetScope and not develop a model for the desired sensor? Why not use machine learning? How does taking this approach affect the accuracy of the final result? If the main objective is the harmonization method, it should be clearer.
• Structure: The structure and outline of the article should be revised. I believe sections 4-7 should be subsections of Methodology. Also, please revise the whole article to follow a consistent method for section and subsection numbering and titling.
• Introduction: The introduction provides a good background of data harmonization. However, there is not enough literature review on recent and similar studies. Also, the main objectives of this study are unclear. If this article is focused on advancing harmonization methods, the other recently developed methods (numeric, machine learning, etc.) should be reviewed to highlight the novelty of this study. Moreover, if the application of this study is on Biomass mapping and adopting the pre-developed model from PlanetScope, much information about this subject should be added to this section. There is no review of biomass mapping methods and models.
• Ground field surface reflectance data: Please add more details about the ground data. For example, how many data points were collected?
• Results and evaluation: It is unclear to me how accurate the final product and grassland biomass maps were improved using this approach. Also, there is no ground reference data to evaluate the produced maps, and there is uncertainty regarding applying a model with the proposed harmonization to another dataset. There are not only band and spectral differences but also differences in spatial and time-space. This model might have been developed for biomass in certain regions on a certain timeframe, and applying it to this specific region without ground reference biomass data will create uncertainty in the final results.

 

• Minor points:

L64: Landsat and Sentinel-2 have a combined revisit time of 8 and 5 days, respectively.

Fig1: I suggest using colors to separate different stages of the flowchart, such as data, preprocessing, results, evaluation, etc.

L216: Subsections should be numbered and follow a consistent styling.

Author Response

Dear Reviewer 2,

Thank you for your thorough review and valuable feedback on my manuscript. I am uploading a revised version of the manuscript along with a detailed response to your comments. In the revised manuscript, I have carefully addressed all your suggestions to enhance clarity, structure, and scientific rigor. Key updates include refining the Abstract and Introduction to clearly articulate our objective of achieving accurate and frequent grassland biomass estimation using VIIRS through spectral harmonization, reorganizing the Methodology section for improved flow and consistency, and strengthening the Results section with a detailed uncertainty analysis (e.g., RMSE of 11.6 g/m², R² of 0.92, mean percentage difference of 10.74%). The title has been updated to "Adapting High-Resolution PlanetScope Biomass Model to Low-Resolution VIIRS Imagery Using Spectral Harmonization: A Case of Grassland Monitoring in Mongolia," reflecting both the methodological innovation and its application, as detailed in the response document.

Per your guidance, the Introduction now includes a broader literature review on harmonization and biomass mapping methods, the manuscript structure has been revised with consistent section numbering, and additional details on ground data have been added. Figures and tables (e.g., color-coded flowchart) have been adjusted for clarity and readability. The English has also been refined throughout to improve expression. I believe these revisions significantly enhance the manuscript’s quality and address your concerns effectively. Please let me know if further clarifications or adjustments are needed. I deeply appreciate your time, expertise, and insightful comments, which have greatly improved this work.

Sincerely,

Mr. Margad-Erdene Jargalsaikhan

Corresponding Author

PhD Student

Yamaguchi University, Japan

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript refers to integration of high- and low-resolution data using dedicated tools for vegetation monitoring and, more specifically, different types of grasslands in Mongolia.

The applied techniques for harmonisation procedures, and related difficulties, for data coming from sensors having different spectral and spatial resolutions are very detailed and well explained throughout all the manuscript making it fluent to be understood by the reader.

Study area information is fully provided with details of location and characteristics of validation points.

Differentiation of different types of primary grasslands results very interesting to go deeper into land cover classification analysis.

Results are well presented in terms of tables and figures while it results very interesting the insertion of the subchapters Potential Limitations and Future Directions in the Discussion.

English is fluent and no correction is required, References are exhaustive and well cited in the manuscript.

Author Response

Dear Reviewer 3,

We sincerely thank you for your positive and encouraging feedback on our manuscript. We are delighted that you found the integration techniques, study area details, and differentiation of grassland types to be well-presented and informative. Although no major revisions were requested, we have uploaded a revised version of the manuscript with several improvements to enhance clarity, organization, and readability. These include refining the Abstract and Introduction for clearer objectives, restructuring the Methodology section for better flow, and adding uncertainty analysis (e.g., RMSE of 11.6 g/m², R² of 0.92, mean percentage difference of 10.74%) to the Abstract, Discussion, and Conclusion for increased rigor. The title has also been updated to "Adapting High-Resolution PlanetScope Biomass Model to Low-Resolution VIIRS Imagery Using Spectral Harmonization: A Case of Grassland Monitoring in Mongolia" to emphasize methodological innovation and applicability.

We believe these enhancements further strengthen the manuscript while preserving its original strengths. We truly appreciate your thoughtful comments and support, which have been invaluable to this work. Please let us know if any additional clarifications are needed.

Sincerely,

Mr. Margad-Erdene Jargalsaikhan

Corresponding Author

PhD Student

Yamaguchi University, Japan

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thanks for the authors’ great efforts to address my concerns. The revised manuscript looks much better. I do not have further comments and recommend publishing this manuscript.