Water Multi-Parameter Sampling Design Method Based on Adaptive Sample Points Fusion in Weighted Space

Round 1

Reviewer 1 Report

Document: remotesensing-1736927

Article: Water Multi-Parameter Sampling Design Method Based on 2Adaptive Sample Points Fusion in Weighted Space

Review Report

The topic of the article is relevant in the field of remote sensing of water quality. The authors have proposed an approach for designing a spatially representative sampling plan of multiple water parameters. The proposed approach can be useful to improve the spatial representativeness of in situ multiple water parameters for ensuring accuracy of remote sensing product retrieval and verification. The conclusions are consistent with the evidence and arguments presented and they address the main question posed. The references are appropriate. However, the manuscript still has some obvious deficiencies. Even though the idea is interesting, there are some major weaknesses in the manuscript. I would recommend major revision:

1. The authors seem to ignore certain realities of water quality sampling. This is clear in figure 8 where they show different sampling locations for each parameter. In water quality sampling the sample is taken from a certain location and is usually analyzed for multiple parameters (in-situ or at the lab). How does the authors justify the claim that the parameters were evaluated at different locations?
2. It is also unclear how the parameter values where handled in the calculation of the adaptive weight sampling point. A numerical example is needed to clarify how different parameters (with different units) were aggregated in the adaptive sampling point. This should be added to the methods section.
3. Information on the data used in the study is scattered throughout the manuscript. In one section in the methodology the reader has to see: the number of sampling points, their distribution, where the data was obtained, any assumptions regarding the data, preliminary statistics of the data (mean standard deviation, etc.).
4. Line 231 “We assume a set of simulated data evenly distributed…” if is unclear why this assumption is made. I think the authors can clarify that in the data section in the methods.
5. To describe the heterogeneity of the spatial distribution characteristics of each parameter, the authors used K-means to perform spatial clustering. K-means algorithm is very sensitive to initial guess of centroids, because of that it may trap in local minima in place of global minima. How did the authors tackle this problem?
6. Why did the author use different satellite product for sampling design and validation? For instance, at Nanyi lake, the author used Sentinel 2 for sampling design whereas another satellite product (GF-6) was used for validation. The same for the Bosten lake, why did the authors use GF1 and GF1B for sampling design and validation. Any specific reason?
7. The author uses kriging interpolation method to obtain the interpolation surface of the sampling area. Why did they select this method over other interpolation techniques?
8. In Kriging interpolation, variogram models control the Kriging weights. How did the authors select the best variogram models for different parameters? Selection of proper variogram models may improve the results.
9. Since the authors considered only three parameters, the adaptive weights were assigned according to the properties of the triangles because the spatial distribution of the parameters is in the shape of triangle. What if multi-parameter weight space is composed of more than 3 parameters? How should one consider the adaptive weights for such scenario? This is a relevant question since water quality sampling typically includes many parameters.
10. The authors repeat the methodology, and even mention new information on the methods applied, in the results section. This is unacceptable, please move lines 240-246, lines 258-264, lines 333-339 to the methods section.
11. The discussion section lines 405-423 is repeated, please remove.
12. The discussion is weak. Not one reference is included in the discussion, so unless the authors are claiming that this is the first effort in the field of water sampling optimization (it is not) they have to revise the discussion to include comparison with previous research.
13. The manuscript needs considerable language revisions. There are many grammatical and typing errors. To mentioned a few:
    1. Line 13, 49 water quality tests (not experiments)
    2. Line 30 “evolution” consider changing to a more appropriate term
    3. Line 31 “water resources”
    4. Line 45 “scientificity” consider changing to a more appropriate term
    5. Equation 3 is incorrect in the (x,y) coordinates
    6. Line 294 incomplete sentence “indicating uns”
    7. line 45 “As” should be “as”;
    8. line 269 and 287 start with capital letter after full stop.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

1. The manuscript presents water multi-parameter sampling design method based on adaptive sample points fusion in weighted space, which is interesting. The subject addressed is within the scope of the journal.
2. However, the manuscript, in its present form, contains several weaknesses. Appropriate revisions to the following points should be undertaken in order to justify recommendation for publication.
3. Full names should be shown for all abbreviations in their first occurrence in texts. For example, SSA in p.2, GA in p.2, PSO in p.2, GF in p.3, etc.
4. For readers to quickly catch your contribution, it would be better to highlight major difficulties and challenges, and your original achievements to overcome them, in a clearer way in abstract and introduction.
5. It is shown in the reference list that the authors have several publications in this field. This raises some concerns regarding the potential overlap with their previous works. The authors should explicitly state the novel contribution of this work, the similarities, and the differences of this work with their previous publications.
6. 1 - adaptive sample points fusion in weighted space is adopted for the water sampling design method. What are other feasible alternatives? What are the advantages of adopting this approach over others in this case? How will this affect the results? The authors should provide more details on this.
7. 1 - chlorophyll a, total suspended matter, and Secchi-disk Depth are adopted as the water parameters. What are the other feasible alternatives? What are the advantages of adopting these parameters over others in this case? How will this affect the results? More details should be furnished.
8. 3 - Nanyi Lake and Bosten Lake are adopted as the case studies. What are other feasible alternatives? What are the advantages of adopting these case studies over others in this case? How will this affect the results? The authors should provide more details on this.
9. 3 - Sentinel-2 and GF high-resolution satellite remote sensing image data and in-situ data adopted as the datasets. What are the advantages of adopting these datasets over others in this case? How will this affect the results? The authors should provide more details on this.
10. 4 - flowchart as shown in Figure 2 is adopted for the methodology in this study. What are the advantages of adopting this approach over others in this case? How will this affect the results? The authors should provide more details on this.
11. 5 - K-means is adopted to perform spatial clustering. What are the advantages of adopting this approach over others in this case? How will this affect the results? The authors should provide more details on this.
12. 5 - SSA, GA, PSO are adopted as feasible water single-parameter sampling methods. What are the other feasible alternatives? What are the advantages of adopting these intelligent optimization methods over others in this case? How will this affect the results? More details should be furnished.
13. 5 - the mean square error is adopted as the objective function. What are the advantages of adopting this metric over others in this case? How will this affect the results? The authors should provide more details on this.
14. 7 - four evaluation criteria are adopted to evaluate the model performance. What are the other feasible alternatives? What are the advantages of adopting these evaluation criteria over others in this case? How will this affect the results? More details should be furnished.
15. 8 - six sampling methods are adopted for effectiveness evaluation. What are the other feasible alternatives? What are the advantages of adopting these methods over others in this case? How will this affect the results? More details should be furnished.
16. Some key model parameters are not mentioned. The rationale on the choice of the set of parameters should be explained with more details. Have the authors experimented with other sets of values? What are the sensitivities of these parameters on the results?
17. Some assumptions are stated in various sections. Justifications should be provided on these assumptions. Evaluation on how they will affect the results should be made.
18. The discussion section in the present form is relatively weak and should be strengthened with more details and justifications.
19. Moreover, the manuscript could be substantially improved by relying and citing more on recent literatures about contemporary real-life case studies of water quality modeling such as the followings. Discussions about result comparison and/or incorporation of those concepts in your works are encouraged:

• Tiyasha, et al., “A survey on river water quality modelling using artificial intelligence models: 2000-2020,” Journal of Hydrology 585: 124670 2020.
• Zhou, Y.L., et al., “Real-Time Probabilistic Forecasting of River Water Quality under Data Missing Situation: Deep Learning plus Post-Processing Techniques,” Journal of Hydrology 589: 125164 2020.
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• Alizadeh, M.J. et al., “Toward multi-day-ahead forecasting of suspended sediment concentration using ensemble models,” Environmental Science and Pollution Research 24 (36): 28017-28025 2017.

20. Some inconsistencies and minor errors that needed attention are:

• Replace “…Nanyi lake and Bosten lake…” with “…Nanyi Lake and Bosten Lake…” in lines 97-98 of p.3
• Replace “…Nanyi lake and Bosten lake…” with “…Nanyi Lake and Bosten Lake…” in lines 98-99 of p.3

21. Some recommendations are made for further investigation. Why are they not performed in this study? More justifications should be furnished on this.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors successfully addressed the comments. I accept the manuscript in its current form.

Reviewer 2 Report

The revised paper has addressed all my previous comments, and I suggest to ACCEPT the paper as it is now.

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.