Detecting Water Hyacinth Infestation in Kuttanad, India, Using Dual-Pol Sentinel-1 SAR Imagery
, Vahid Akbari 2, Armando Marino 1, G. Nagendra Prabhu 3, Deepayan Bhowmik 2, Srikanth Rupavatharam 4, Aviraj Datta 4, Adam Kleczkowski 5, J. Alice R. P. Sujeetha 6, Girish Gunjotikar Anantrao 6, Vidhu Kampurath Poduvattil 6, Saurav Kumar 7, Savitri Maharaj 2 and Peter D. Hunter 1
Round 1
Reviewer 1 Report
This manuscript focuses on detecting water hyacinth in Vembanad Lake, Kuttanad, India. The authors first determined the best SAR detector and corresponding threshold to identify the water hyacinth, then generated the heat map to present the occurrence of water hyacinth during 2019-2021. The overall idea for this study is well. However, the most issue I concern is the innovation. As far as I know, there is little difficulty in technology for distinguishing the water hyacinth from clean water, the only two targets in this study. It is easily to discriminate water hyacinth with a simple and clear threshold as the figure 5 and 6 present. Therefore, the innovation, the contribution, and technologically advance should be strengthened in every place of the manuscript. Besides, the manuscript was organized awkward, represented by some unreasonable contents, tables and figures (see below). Therefore, from my point of view, at least a major revision is needed.
(1)Line 73-74: this sentence should be placed to the previous paragraph instead of an individual point.
(2)Line 110: author name should be given here instead of a reference number only, other places also have the same problem, please check and modify.
(3)Line 119 and 123: this part mainly focus the optical systems, however, some studies (combined) using ENVISAT image (SAR). These studies are suggested to place to the next part of Radar system. Optical image time-series references should be added here. Some typical references are provided below:
[1] Sun C, Li J, Liu Y, et al. Plant species classification in salt marshes using phenological parameters derived from Sentinel-2 pixel-differential time-series[J]. Remote Sensing of Environment, 2021, 256: 112320.
[2] Campbell, Anthony Daniel, and Yeqiao Wang. "Salt marsh monitoring along the mid-Atlantic coast by Google Earth Engine enabled time series." PloS one 15.2 (2020): e0229605.
[3] Zhang, Xi, et al. "Quantifying expansion and removal of Spartina alterniflora on Chongming island, China, using time series Landsat images during 1995–2018." Remote sensing of environment 247 (2020): 111916.
(4)Line 178-201: this part is suggested to place to the section of material and methodology
after satellite data
(5)Line 257-258: does the values from the pixel obey a normal distribution? the authors should provide the details
(6)Line 264-265: the formula should be numbered, other places also have the same problem, please check and modify.
(7)Figure 2: why there are two individual workflows? and some steps from the two worflows is identical, which can be combined
(8)Figure 5 and 6: the extents for (a) and (b) are suggested to be consistent for finding out the location of the polygon samples easily.
(9)Table 2: I wonder that the difference between table 1 and table 2, I think the contents these table presented are similar
(10)Figure 10: I don't see the enough curves corresponding to the legend in the figure
(11)Figure 10 and 11: I wonder that the difference between figure 10 and figure 11, I think the contents the two figure presented are similar. One of them could consider to be removed, or at least, combining the two figures into one
(12)Line 486 and 523: the titles are very strange, please change.
(13)Figure 12 and 13: the same problem to (11)
(14)Figure 15 and 16: the same problem to (11)
(15)Figure 16: I just miss the distribution of water hyacinth from each phrase.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Author,
I have reviewed the paper "Detecting Water Hyacinth Infestation in Kuttanad, India, Using Dual-Pol Sentinel-1 SAR Imagery". The aims of the paper are germane with Remote sensing applications topic, in this form of article fits with the international scientific standards. The paper is written with a moderate English level. The contribution of this paper to the scientific knowledge is good. Although, in my opinion, there some important flaws and I suggest the corrections in the comments in the attached file.
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
None.
Author Response
As there are no comments or suggestions here, we thank you very much for your comments in the previous reviews that have helped improve this paper. We kindly appreciate it.
Many thanks,
Morgan
