Automated versus Manual Mapping of Gravel Pit Lakes from South-Eastern Romania for Detailed Morphometry and Vegetation

Round 1

Reviewer 1 Report

The paper entitled Automated versus manual mapping of small gravel pit lakes from south-eastern romania for detailed morphometry and vegetation, deals with methods for assessing the spatial distribution and morphometric characteristics of lakes. This is a very important and topical subject. In recent years, we have observed very dynamic changes in the hydrological situation in many regions of the world. Any work in this field is therefore very valuable.
The introduction is short but contains a large number of reports from this field. It provides a sufficient introduction to the problems of the study. Is it advisable to cite so many publications older than 50 years? The aim and scope of the study are clear from it. Is it necessary to narrow the title of the study to small lakes?
The method of research is presented correctly. Does the information in chapter 2.1. Study area relate to the method of research? I do not think so and propose that it be removed from Chapter 2.
The results of the study are presented graphically and described very well. Their interpretation is clear and unambiguous. Detailed comments:
Fig. 3 and Fig. 5 Are the parameters of the regression models significantly different from zero? 
Throughout the paper in the notation of figures replace , with . (Fig. 2; Fig. 3; Fig. 5).
Why did you wait so long to publish the results of the study? What is the necessary effort to obtain results with this method? Comparison to other known methods. 
Table 4: Which of the presented correlation coefficients are statistically significant? 
I suggest that the description regarding the strengths and weaknesses of the proposed method be expanded in the article. Comparisons to other methods. There is also a lack of information on further research directions of the authors of the paper in this area. 
Conclusions are very short and general. You have done a lot of work and please expand the conclusions. 

Overall, I rate the work very well. 

Author Response

Review Report Form

Open Review

( ) I would not like to sign my review report
(x) I would like to sign my review report

English language and style

( ) Extensive editing of English language and style required
( ) Moderate English changes required
( ) English language and style are fine/minor spell check required
(x) I don't feel qualified to judge about the English language and style

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	(x)	( )	( )
Are all the cited references relevant to the research?	(x)	( )	( )	( )
Is the research design appropriate?	(x)	( )	( )	( )
Are the methods adequately described?	(x)	( )	( )	( )
Are the results clearly presented?	( )	(x)	( )	( )
Are the conclusions supported by the results?	( )	(x)	( )	( )

Comments and Suggestions for Authors

The paper entitled Automated versus manual mapping of small gravel pit lakes from south-eastern romania for detailed morphometry and vegetation, deals with methods for assessing the spatial distribution and morphometric characteristics of lakes. This is a very important and topical subject. In recent years, we have observed very dynamic changes in the hydrological situation in many regions of the world. Any work in this field is therefore very valuable.

Answer: Thank you very much for your comments that helped us to improve our original manuscript

The introduction is short but contains a large number of reports from this field. It provides a sufficient introduction to the problems of the study. Is it advisable to cite so many publications older than 50 years? The aim and scope of the study are clear from it. Is it necessary to narrow the title of the study to small lakes?

Answer: Following your suggestion we deleted “small” from the title. Thank you ! Thank you for question about older references. It is possible to delete - Gravelius 1914, Hutchinson 1957, Miller 1953 ... equations are very used, and sometimes some authors do not cite theses references - we believe that is no ethical to not provide the name of the authors that elaborated them.

The method of research is presented correctly. Does the information in chapter 2.1. Study area relate to the method of research? I do not think so and propose that it be removed from Chapter 2.

Answer: Following your observation, we made a separate section removed from Chapter 2. Thank you for mentioning it.

The results of the study are presented graphically and described very well. Their interpretation is clear and unambiguous.

Answer: Thank you for your evaluation!

Detailed comments:
Fig. 3 and Fig. 5 Are the parameters of the regression models significantly different from zero? 

Answer: Yes, because R2 are >0.8

Throughout the paper in the notation of figures replace, with . (Fig. 2; Fig. 3; Fig. 5).

Answer: we modified accordingly

Why did you wait so long to publish the results of the study? What is the necessary effort to obtain results with this method? Comparison to other known methods. 

Answer: Yes, your comment is pertinent but COVID created unexpected situation and a low productivity sometimes (we start our study in April 2020 because we are in lockdown and was not possible to go on field but ..). Comparison to other known methods are prepared for the next research.

Table 4: Which of the presented correlation coefficients are statistically significant? 

Answer: Thank you, we added the confidence level

I suggest that the description regarding the strengths and weaknesses of the proposed method be expanded in the article. Comparisons to other methods. There is also a lack of information on further research directions of the authors of the paper in this area. 
Conclusions are very short and general. You have done a lot of work and please expand the conclusions. 

Answer: We included more information about strength and weaknesses. Furthermore, we included two supplementary approaches to assess LAI in the study area (PROBA-V and MODIS LAI products).

Overall, I rate the work very well. 

Thank you for your valuable comments!

 

Submission Date

06 April 2022

Date of this review

19 Apr 2022 09:40:10

Author Response File: Author Response.docx

Reviewer 2 Report

The use of remotely sensed data for environmental and ecological assessment has recently become an active area of research in water research and management. Satellite imagery has emerged as another tool for monitoring lakes and water reservoirs, providing high spatial and temporal resolution. However, their use is affected by many organizational and technical problems.

The presented manuscript concentrates on using remote sensing methods for analyzing the morphometric characteristics and the spatio-temporal distribution of gravel pit lakes. The authors have acquired satellite images from various missions and proposed a methodology to process them.

The authors put much effort into creating this paper, and the results can be interesting. However, the overall presentation requires further work to improve the presented work's structure and clarity.

In the current form, the paper seems more like a description of a conducted technical project than a research paper. Unfortunately, when reading the entire paper, it was still unclear what research question this paper was trying to answer.

The Introduction is too general. There is only a small discussion about similar research utilizing photogrammetric images with RGB, multispectral, or hyperspectral bands. To date, many articles have been published on detecting shorelines and monitoring spatio-temporal water changes using remote sensing, GIS and Artificial Intelligence (AI) methodology. I would recommend adding this information to this section of the article. In this section, the novelty of this article against others on the topic should also be clearly described.

The process of describing the data processing methodology is missing details. The authors should improve this section. The text lacks details on the process of data acquisition and technical specification of satellite images used in the measurement. It is not clear how the data was analyzed. It will be good for readers if the authors include a new figure which explains the processing strategy (flow chart).

Other doubts are related to data sources. The author declares that true-color satellite images provided by Google Earth were used. The images displayed on Google Earth usually are adjusted to their best visual appearance. Contrary to other commercial satellite imagery products, images provided by Google Earth are true-color visible spectrum satellite imagery without the original multispectral band data. This is a significant limitation to object recognition. Without non-visible bands, such as infrared or near-infrared, it could be hard to distinguish objects and changes. Should the author explain this issue and describes acquisition/preprocessing steps for all images (color balancing, geometrical registration, warping, mosaic processing).

The authors briefly presented LAI analysis. This is now a standard procedure both in industry and academia. The text lacks an explanation of why and how the coefficient was calculated. There is no information on how LAI indices can be used in spatio-temporal analyses. The authors have only shown some preliminary results, while they declare vegetation analysis as one of the research issues in the title. Please consider rewriting this section.

The authors often use the terms lakes and ponds interchangeably in the text. In practice, a body of water is called a pond when it is small and enclosed, while a lake is large and open. Could the authors standardize the convention of using these terms in the text?

The maps in the figures are not of good quality. The area of interest is too small (it should be zoomed in more). The labels are too small. Please consider changing size and location to improve readability. Bright, flashy colors such as on the map should not be used.

Some specific comments, including the addition and modification of figures and table, are listed below.

• Figure 1. This figure is unreadable. The maps and objects of interest are too small. Bright, flashy colors such as on the map and the following figures should not be used.
• Row 273. (fig. 1c) – missing caption a, b, c, d in Figure 1.
• Rows 294-295 "The validation of the surface size was done crosswise using 209 lakes chosen randomly whose contours were similar". Could the authors explain why they chose a sample of 209 water bodies for the analysis?
• The authors refer/use the expression "resolution of Google Earth images" in the text, while it is not specified. This does not allow for evaluating the results obtained by manual vectorization of the water reservoir boundaries.
• Row 319 "Evaluation of the spatial distribution of gravel pits using Sentinel 2A datasets". Do you analyze gravel pits or gravel pits lakes?
• Row 350 "An analysis of the direction of the dominant winds ..". Could the authors specify where such analyses have been shown?

English writing should be checked, and improve the connection between sentences and paragraphs.

The manuscript should be rebuilt and corrected to improve its scientific level. I recommend considering the publication after major revision.

Author Response

Review Report Form

Open Review

(x) I would not like to sign my review report
( ) I would like to sign my review report

English language and style

( ) Extensive editing of English language and style required
(x) Moderate English changes required
( ) English language and style are fine/minor spell check required
( ) I don't feel qualified to judge about the English language and style

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	( )	(x)	( )
Are all the cited references relevant to the research?	( )	( )	(x)	( )
Is the research design appropriate?	( )	(x)	( )	( )
Are the methods adequately described?	( )	(x)	( )	( )
Are the results clearly presented?	( )	( )	( )	( )
Are the conclusions supported by the results?	( )	(x)	( )	( )

Comments and Suggestions for Authors

The use of remotely sensed data for environmental and ecological assessment has recently become an active area of research in water research and management. Satellite imagery has emerged as another tool for monitoring lakes and water reservoirs, providing high spatial and temporal resolution. However, their use is affected by many organizational and technical problems. The presented manuscript concentrates on using remote sensing methods for analyzing the morphometric characteristics and the spatio-temporal distribution of gravel pit lakes. The authors have acquired satellite images from various missions and proposed a methodology to process them. The authors put much effort into creating this paper, and the results can be interesting. However, the overall presentation requires further work to improve the presented work's structure and clarity. In the current form, the paper seems more like a description of a conducted technical project than a research paper. Unfortunately, when reading the entire paper, it was still unclear what research question this paper was trying to answer. The Introduction is too general. There is only a small discussion about similar research utilizing photogrammetric images with RGB, multispectral, or hyperspectral bands. To date, many articles have been published on detecting shorelines and monitoring spatio-temporal water changes using remote sensing, GIS and Artificial Intelligence (AI) methodology. I would recommend adding this information to this section of the article. In this section, the novelty of this article against others on the topic should also be clearly described.

Answer: Thank you very much for your comments that helped us to improve our original manuscript. We added more info’s in section Introduction and Methods

The process of describing the data processing methodology is missing details. The authors should improve this section. The text lacks details on the process of data acquisition and technical specification of satellite images used in the measurement. It is not clear how the data was analyzed. It will be good for readers if the authors include a new figure which explains the processing strategy (flow chart).

Answer: Thank you for suggestions - we added a flowchart and more info’s in the section Methods (please see the track changes)

Other doubts are related to data sources. The author declares that true-color satellite images provided by Google Earth were used. The images displayed on Google Earth usually are adjusted to their best visual appearance. Contrary to other commercial satellite imagery products, images provided by Google Earth are true-color visible spectrum satellite imagery without the original multispectral band data. This is a significant limitation to object recognition. Without non-visible bands, such as infrared or near-infrared, it could be hard to distinguish objects and changes. Should the author explain this issue and describes acquisition/preprocessing steps for all images (color balancing, geometrical registration, warping, mosaic processing).

Answer: From Google Earth, gravel pit lakes contours were extracted through manual vectorization, exported in .kml format and transformed into shapefile in ArcGIS 10.8  (this is the reason for the title of manuscript – manual vs. automatic).  The resolution of the images (given the large layout of the study area) is uneven and depends on the sources used by Google Earth (Landsat / Sentinel / CNES / Airbus / Maxar Techologies from 30-2.5 m).

The authors briefly presented LAI analysis. This is now a standard procedure both in industry and academia. The text lacks an explanation of why and how the coefficient was calculated. There is no information on how LAI indices can be used in spatio-temporal analyses. The authors have only shown some preliminary results, while they declare vegetation analysis as one of the research issues in the title. Please consider rewriting this section.

Answer: Following your recommendations, we have improved the LAI description both in introduction and methodology.

We have extended the previous analysis by including MODIS and PROBA-V assessments of LAI.

Also, we included the missing reference: Gitelson, A.A. and Merzlyak, M.N. (1998) Remote Sensing of Chlorophyll Concentration in Higher Plant Leaves. Advances in Space Research, 22, 689-692.
http://dx.doi.org/10.1016/S0273-1177(97)01133-2

We have cited more relevant papers and resources from literature.

Thank you!

The authors often use the terms lakes and ponds interchangeably in the text. In practice, a body of water is called a pond when it is small and enclosed, while a lake is large and open. Could the authors standardize the convention of using these terms in the text?

Answer: Thank you for comment. We use the same term in all manuscript: gravel pit lakes

The maps in the figures are not of good quality. The area of interest is too small (it should be zoomed in more). The labels are too small. Please consider changing size and location to improve readability. Bright, flashy colors such as on the map should not be used.

Answer: We tried to improve the readability of the maps following your recommendations. We included more information from 2 other missions (PROBA-V and MODIS) to supplement the previous data. We hope that the current version is reaching your expectations.

Some specific comments, including the addition and modification of figures and table, are listed below.

• Figure 1. This figure is unreadable. The maps and objects of interest are too small. Bright, flashy colors such as on the map and the following figures should not be used.
• Row 273. (fig. 1c) – missing caption a, b, c, d in Figure 1.

Answer: thank you - We changed the figure and we added figure caption a, b, c

 

• Rows 294-295 "The validation of the surface size was done crosswise using 209 lakes chosen randomly whose contours were similar". Could the authors explain why they chose a sample of 209 water bodies for the analysis?

Answer: It was difficult in some situations because the number of lakes extracted is different. The difficulty was mainly for the lakes extracted from Landsat because the lakes with very small areas and short distances between them were transformed into a single polygon.

 

• The authors refer/use the expression "resolution of Google Earth images" in the text, while it is not specified. This does not allow for evaluating the results obtained by manual vectorization of the water reservoir boundaries.

Answer: The resolution of the images (given the large layout of the study area) is uneven and depends on the sources used by Google Earth (Landsat / Sentinel / CNES / Airbus / Maxar Techologies from 30-2.5 m) and zoom in / out. We use the best resolution available at that moment (<10 m).

• Row 319 "Evaluation of the spatial distribution of gravel pits using Sentinel 2A datasets". Do you analyze gravel pits or gravel pits lakes?

Answer: thank you for comment, we correct the errors (gravel pit lakes)

• Row 350 "An analysis of the direction of the dominant winds ..".Could the authors specify where such analyses have been shown?

Answer: Thank you – we add info about wind speed and direction on figure 2a

English writing should be checked, and improve the connection between sentences and paragraphs.

Answer: We have made an extended editing and we hope that the current version is reaching the required standards.

The manuscript should be rebuilt and corrected to improve its scientific level. I recommend considering the publication after major revision.

Thank you for your valuable comments!

 

Submission Date

06 April 2022

Date of this review

21 Apr 2022 21:31:39

Author Response File: Author Response.docx

Reviewer 3 Report

First of all, this draft does not comply with the MDPI submission guidelines.

This study is a kind of regional application since it is hard to find the academic novelty of the contents and results in the research. It is difficult for the general reader to understand the local features of the study area.

The application of optical satellite imagery does not reflect the recent trend, the application of SAR imagery to detect water bodies.

The contents of Figure 3 are not meaningful ones in the satellite image processing.

The calculation of the LAI is essential, but it seems that the formula used in this study is not a suitable LAI extraction scheme. As well, there is no description of the LAI coefficients. The cited article by Gitelson & Merzlyak (1998) does not appear in the reference.

Author Response

-

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

 

The manuscript “Automated versus manual mapping of small gravel pit lakes from south-eastern Romania for detailed morphometry and vegetation” has been significantly improved after major revision.

I would recommend publishing it in Water.

Author Response

Thank you so much for reviewing our manuscript.

 

Respectfully,

the authors.

Reviewer 3 Report

Overall, the paper's content is distracting, so it is not easy to understand what is novelty and originality.

In Figure 1, there is no explanation for which preprocessing of the satellite image was done.

The main results are visually presented in Figures 8, 9, and 10, but quantitative analysis of results such as a sort of cause-effect analysis or correlation analysis is insufficient.

There are 113 references, too many. It needs to be reduced.

Author Response

Review Report Form

 

Open Review

( ) I would not like to sign my review report

(x) I would like to sign my review report

English language and style

( ) Extensive editing of English language and style required

( ) Moderate English changes required

( ) English language and style are fine/minor spell check required

(x) I don't feel qualified to judge about the English language and style

            Yes      Can be improved         Must be improved       Not applicable

Does the introduction provide sufficient background and include all relevant references?

            ( )        (x)       ( )        ( )

Are all the cited references relevant to the research?

            ( )        ( )        (x)       ( )

Is the research design appropriate?

            ( )        (x)       ( )        ( )

Are the methods adequately described?

            ( )        ( )        (x)       ( )

Are the results clearly presented?

            ( )        ( )        (x)       ( )

Are the conclusions supported by the results?

            ( )        ( )        (x)       ( )

 

Comments and Suggestions for Authors

 

Overall, the paper's content is distracting, so it is not easy to understand what is novelty and originality.

 

In Figure 1, there is no explanation for which preprocessing of the satellite image was done.

 

The main results are visually presented in Figures 8, 9, and 10, but quantitative analysis of results such as a sort of cause-effect analysis or correlation analysis is insufficient.

 

There are 113 references, too many. It needs to be reduced.

 

Submission Date

06 April 2022

Date of this review

26 May 2022 02:41:08

 

Overall, the paper's content is distracting, so it is not easy to understand what is novelty and originality.

Answer: We explained the utility of our approach below the objective of our study:

In Romania, an inventory of gravel pits is not available and our approach comes up with a solution to create a comprehensive dataset that contains useful information regarding the conformity with the Mining Law 85/2003 and specifications stipulated in GD 445/2009 that regulate their activity, the spatial extent, how long does the vegetation installed spontaneously recover after the finishing of exploitation, and the assessment of the direct or indirect impact on human settlements, flora, fauna, soil, water, air, and material goods.

 

Furthermore, we included a correlation analysis as you have suggested to compare the LAI datasets. We hope that this addition will increase the scientific merit of the manuscript. Thank you for your useful suggestions that have helped us to improve our work.

 

In Figure 1, there is no explanation for which preprocessing of the satellite image was done.

Answer:  Google Earth images were not preprocessed.

The images Landsat, Sentinel, MODIS, Proba-V were subject to usual processing: band selection, radiometric correction, projection system etc.

 

The main results are visually presented in Figures 8, 9, and 10, but quantitative analysis of results such as a sort of cause-effect analysis or correlation analysis is insufficient.

 

Answer: To fill this gap, we included the following in Methods:

 

Correlation analysis between the obtained LAI datasets from various satellite missions was performed using the following steps: 1) application of Geostatistical Analyst Tool – Simulation – Extract values to table, for each subbasin; 2) the obtained LAI indicators for each subbasin were averaged to obtain a single indicator for the study area; 3) logarithmic trendlines were plotted for each time series and correlation between the time series were performed.

 

Then, in the results section, we included Figure 11 showing the logarithmic trendlines for each dataset for March-August period and correlations between each mission.

 

The included text is “Figure 11 shows a comparison between the indicators extracted for each month using the Geostatistical Analyst Tool for each component subbasin in the entire study area. A similar logarithmic trendline was observed for each time series (PROBA-V, MODIS, Sentinel 2A) with significant R2. More analytical assessments will be performed in future approaches to improve the accuracy of indirect algorithms based on NDVI-LAI regressive models since the Sentinel 2A time series tends to underestimate the averaged integrative LAI between March and August 2019 (1.9; St. Dev. = 0.91) compared to MODIS (2.04; St. Dev. = 0.95) and PROBA-V (2.2; St. Dev. =1.01). PROBA-V time series contained the maximum integrative values of LAI.

 

Obviously, a calibration study is required using longer time series, but this was not the main purpose of this work. One of the objectives was to observe how LAI can be estimated by relevant and trustful sources of vegetation assessment from satellite missions. Based on the correlations’ results it can be seen that the trends were similar with close insights according to the field reality in the study area.  “

 

There are 113 references, too many. It needs to be reduced.

Answer:  According to your suggestion, we deleted 22 references, reducing the total under 100 references, which is suitable for a scientific article (the revised version has 92 references).

 

Thank you for your support.

 

Submission Date

06 April 2022

Date of this review

13 Apr 2022 03:59:53

Author Response File: Author Response.docx