Agricultural Monitoring Using Polarimetric Decomposition Parameters of Sentinel-1 Data

Round 1

Reviewer 1 Report

Estimating crop physical and chemical parameters using remote sensing technology is an important means of crop growth monitoring. At present, the research in this area is mainly based on the visible near infrared band. In this paper, the potential of temporal profiles of polarimetric decomposition parameters of Sentinel-1 to monitor crop parameters on agricultural fields was analyzed. I think this is a meaningful attempt and worth publishing in this journal.

However, there were some issues with the manuscript：

1)      Abstract: The current way of expression makes it difficult for readers to read. It needs further refinement. After introducing the relevant research methods, the paper should briefly introduce the conclusions obtained, and finally explain the significance of this study.

2)      Figure 4：Figure 4 shows the graph of different growth periods of wheat and barley, but does not combine the analysis of two different crops. It is suggested that the crop growth law revealed by the graph should be analyzed briefly.

3)      Section 5.1: In this paper, the time profiles of polarization decomposition parameters of wheat and barley are described respectively. This is too cumbersome. It's better to describe and analyze comprehensively and highlight the key points of this paper.

4)      Section 6: This paper makes a lot of analysis, but the result is not particularly clear. It is suggested to sort out the logical relationship, simplify the content and summarize the conclusion of this paper.

5)      Figure 12: The coefficients of determination in other parts of this paper are in the form of tables, which are expressed by graphs here. What is the reason for this?

6)      Lines 28: “independence”. Initial lowercase.

7)      Line 302: “does no”. Spelling mistakes.

8)      Generally speaking, the author has carried out a detailed study, but the collation of the paper needs to be further strengthened. For example, The form of discussion is adopted in each part of the result and analysis. The advantage is that each specific research detail can be described clearly; the disadvantage is that the discussion does not play its function, that is, to comprehensively and deeply explore the meaning revealed by the research results of the article combined with the literature. It is hoped that the author will further straighten out his thinking and adjust the structure of the paper.

Author Response

Dear Reviewer,

we would like to thank you very much for reviewing our research article “Agricultural Monitoring Using Polarimetric Decomposition Parameters of Sentinel-1 Data” authored by Katharina Harfenmeister, Sibylle Itzerott, Cornelia Weltzien and Daniel Spengler.

We carefully read your suggestions and questions and revised our manuscript accordingly.

Main structural changes have been made concerning the results and discussion parts. As one reviewer suggested, we combined the subsubsections of each results part to have a cleaner structure and a more focused presentation of key findings. The three discussion sections at the end of each results part (former sections 5.1.4, 5.2.3 and 5.3.4) were combined into a new single discussion section 6.

Furthermore, we rewrote abstract and conclusion to concentrate on main results of the study, which was suggested by both reviewers. A new Figure 13 was included to show regression results on a map.

Please find attached the point-by-point responses to your comments as well as the revised manuscript with highlighted changes. Cited line numbers always refer to the revised manuscript.

Sincerely,

Katharina Harfenmeister

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled "Agricultural Monitoring Using Polarimetric Decomposition Parameters of Sentinel-1 Data" is submitted for publication in Remote Sensing (MDPI) journal as a scientific article. The subject involves the use of multitemporal Sentinel-1 data over two crop types and two study sites in NE Germany. The subject involves the use of polarimetric decomposition over dual-polarization acquisition mode of the Sentinel-1 for characterizing growth and reproductive stages as well as the retrieval of biophysical properties. The subject is therefore of great interest for researchers of vegetation, agriculture, change detection, food security, and insurance among other fields. The manuscript tries to explain data processing and make use of field measurements that are costly and time-demanding. However, I faced some difficulties in trying to follow the research in a way to reproduce it. I am also not that confident about all the processing steps and I feel somehow lost in understanding how field measurements were conducted and how long and in which period.

In general, the manuscript is well written and can be recommended for publication after some changes, most of them of Editorial nature. My major concerns are related to the introduction section that is too short. This section could provide a bit more details of the state of the art of research by explaining better (even if shortly) the sensors, frequency, culture, and goals of the studies rather than just citing numbers (references) after a generic sentence. Additionally, the results could explore better the physical mechanisms that occur during the timeframe as the authors did for the ascending and descending modes adding some additional information in brackets. It would be great and very useful if authors could link a bit better the responses to the surface characteristics upon the sensor perspective that were surely noted by the field measurements such as texture pattern, roughness, and moisture. The explanation could also explore more about precipitation events and their impact on the SAR parameters. Finally, I am also missing some SAR subsets and also the retrieved maps generated.

Minor concerns

L15: explain shortly r2 meaning;

L16a: just add a mention of which variables were ranked/selected;

L16b: regression of what?

L19: how much improvements when faced with intensity backscattering alone?

L30: add twin satellites;

L35: I do not like citing papers like this; please add very briefly what references 12 to 18 investigate;

L42: add "although with some limitations";

L56-57: describe better such event in the region (given some numbers, for example, precipitation records);

L67: add general reference for the geological background;

L78: describe better the characteristics of the agricultural fields in terms of their sizes (in hectares);

L79: what do you mean by conventionally? please detail;

L80: what is the the spatial representativity of these fields?

L84: please add the station code for each site and mention the distance from the selected fields;

L101: from all acquisition modes, right?

L103: I did not follow correctly how the biophysical parameters were collected; and how good was GNSS signals and locations;

L108: please detail the sources;

Figure 4: increase the font size of the X- and Y- axis; also the legend; it is quite impossible to read it after printing it;

L126: describe briefly the strategy of data collection and also steps for obtaining these variables;

L136: please detail better "growing degree";

L142: I am just missing a description of where your performed all these steps (100% in SNAP);

L176: add the proper reference;

L178: which DEM was used and where you performed this step? SNAP? Did you use GCPs to assure good overlapping? please comment on co-registration as well;

Figure 5: this figure is not referenced in the main text (I guess somewhere in L190); how confident points and geolocation of the SAR scenes are?

L208: correlation coefficient is R and coefficient of determination is R^2; please add the equations, also for RMSE and RMSE%;

L212: add the equation;

L216: it would be worth to have the comments on the use of intensity backscattering as well; this would show how good polarimetric decomposition methods are in face of direct use of the intensity backscattering alone;

L230: why it tends to rise? please comment on those physical aspects (also for other paragraphs) to better follow the physical mechanisms;

L328: how much this decrease represents?

L380: I get confused from L212;

Table 6: add a note that Table 2 contain the description of the parameters;

L505: add the [44] immediately after the authors; same for other citations;

The conclusion section could be shortened and list all minor findings into a broader perspective. Additionally, the discussion about further research perspectives could be shifted to the discussion section.

Thank you for the opportunity to evaluate this nice and interesting research.

Author Response

Dear Reviewer,

we would like to thank you very much for reviewing our research article “Agricultural Monitoring Using Polarimetric Decomposition Parameters of Sentinel-1 Data” authored by Katharina Harfenmeister, Sibylle Itzerott, Cornelia Weltzien and Daniel Spengler.

We carefully read your suggestions and questions and revised our manuscript accordingly.

Main structural changes have been made concerning the results and discussion parts. As one reviewer suggested, we combined the subsubsections of each results part to have a cleaner structure and a more focused presentation of key findings. The three discussion sections at the end of each results part (former sections 5.1.4, 5.2.3 and 5.3.4) were combined into a new single discussion section 6.

Furthermore, we rewrote abstract and conclusion to concentrate on main results of the study, which was suggested by both reviewers. A new Figure 13 was included to show regression results on a map.

Please find attached the point-by-point responses to your comments as well as the revised manuscript with highlighted changes. Cited line numbers always refer to the revised manuscript.

Sincerely,

Katharina Harfenmeister

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

It has been revised as required and can be published.