Efficient SAR Azimuth Ambiguity Reduction in Coastal Waters Using a Simple Rotation Matrix: The Case Study of the Northern Coast of Jeju Island
Round 1
Reviewer 1 Report
Considering the fact that the signal powers of azimuth ambiguities are concentrated in narrow bands and those of vessels or other true ground targets are dispersed over broad bands, the authors discussed a method to suppress azimuth ambiguities or ghosts in SAR single-look complex (SLC) images in this paper. The suppression of azimuth ambiguities is very important for SAR. Generally speaking, the method is well described. However, this paper lacks of comparison, which makes the authors’ conclusion unconvincing.
- The reviewer wanders to know the meaning of ‘Ψ; λ/2/v*mPRF’ in Equ. (2). The reviewer cannot understand the semicolon here. Overall, the authors should check similar equations in the whole paper.
- Why to choose this value 0.5 in Eq. (6). Besides, the reviewer wanders to know how to determine this weight. Does this weight influence the performance?
- In section 3, the authors tested their method based on real data. It seems that the authors’ method is efficient. However, the readers cannot find the advantage of authors’ method compared to traditional method. Therefore, the authors should compare their method to other traditional methods such as methods in [16, 17, 5, 25] in detail. With this operation, the superiority of authors’ method can be highlighted.
- In the paragraph below Eq. (7), the authors said that ‘The main advantages of the proposed method are its high performance and computational efficiency.’ In general, this paper did not discuss the computation load at all. Therefore, this conclusion is not convincing. The authors should obtain the conclusion based on comparison including computation complexity analysis and processing time.
- Both θ andΨ in Eq. (3) are fixed to 45°. Can both angles choose other angles? Do both angles affect the resultant results? The authors should discuss the influence of both angles on results.
Author Response
- Authors are sincerely grateful for your insightful comments. We appreciate the time and effort that you dedicated to providing feedback on our manuscript which helps make valuable improvements to our paper.
- We have incorporated most of the suggestions made by you, and hope the manuscript after careful revisions meet your high standards.
- A point-by-point response to the reviewer’s comments is in the attached PDF file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors present an interesting paper on a unique approach for the reduction of azimuth ambiguities or ghosts in SAR single-look complex 12 (SLC) images using a simple rotation matrix. The manuscript is well written and should be of great interest to the readers. More clearly results. All figures with charts could be bigger. They are not clear.
Author Response
- Authors are sincerely grateful for your insightful comments. We appreciate the time and effort that you dedicated to providing feedback on our manuscript which helps make valuable improvements to our paper.
Reviewer 3 Report
Dear authors,
You work is interesting and promising, although it is actually an application of a rather simple methodology in a single SAR image. First of all, if you wish to continue trying to publish your work as is, you need to change your title so as to include the specific case study. An indicative title could be: "Efficient SAR Azimuth Ambiguity Reduction in Coastal Waters using a Simple Rotation Matrix: The case study of the northern coast of Jeju Island"
Moreover, you need to make additional effort to prove that your methodology is efficient/effective. You must prove that the weights you used are the most efficient. I provided some examples in the attached document regarding ways to measure the performance of your proposed methodology. One example is the ROC analysis. There are many others that you can use.
Additionally, it is preferable to apply the proposed methodology in other case studies and in a time-series of images so that you fine-tune the weights of 0.5 used in X and Y, and generalize your methodology in order to calibrate and validate your suppression algorithm.
Lastly, boats/ships conducting illegal activities usually turn off AIS. This is not taken into account in your research. You only mention this vaguely in your manuscript. Think of other ways of eliminating ghosts or proving that some items detected are vessels although they were not detected through AIS. You should investigate the use of VHR optical images. There are plenty of examples of optical and radar image fusion in literature.
Please see the rest of my comments/suggestions in the attached document.
Comments for author File: Comments.pdf
Author Response
- Authors are sincerely grateful for your insightful comments. We appreciate the time and effort that you dedicated to providing feedback on our manuscript which helps make valuable improvements to our paper. We have incorporated most of the suggestions made by you as much as possible.
- We have incorporated most of the suggestions made by you, and hope the manuscript after careful revisions meet your high standards.
- A point-by-point response to the reviewer’s comments can be found in the attached PDF file.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Dear authors,
Thank you very much for your effort in incorporating my suggestions to your manuscript. I believe that it has now improved significantly. Your results are now supported by the ROC analysis you carried out and you proved that your methodology worked in your case study, as stated in the revised title of your manuscript. I do not have any further suggestions/comments to make.
