Ground Moving Target Imaging via SDAP-ISAR Processing: Review and New Trends
Round 1
Reviewer 1 Report
Ground moving target imaging has found its main applications in both military and homeland security applications. This paper revisits the latest findings in the area of ground moving target imaging that see the joint application of Space-Time Adaptive Processing and Inverse Synthetic Aperture Radar Imaging. The theoretical aspects analyzed in this paper are supported by practical evidence and followed by application-oriented discussions.
On the whole, this paper is well written, with in-depth theoretical analysis and close connection with practice, which has important theoretical and practical significance for ground moving target imaging research. I would like to recommend that this paper be accepted after English language and style are fine / minor spell check required.
Author Response
The authors would like to thank this reviewer for his/her comments. We have further checked the English usage and corrected some errors/typos throughout the paper.
Reviewer 2 Report
The paper provides readers some insights on moving target indication (MTI) algorithms and could be pretty useful for many of them. The paper is well-written and has organized structure.
I have only one minor comment on this paper: the topic, covered by this paper, is extremely wide which makes the information provided there suitable for book chapter or, at least as an invited paper for an specific journal issue. The majority of techniques, presented in this paper, have been already published by authors (they have 16 self references out of 55) and the authors just combined them all together as one solid block of information.
I'm not sure if the paper's format is suitable for submission as a regular scientific paper, but it will definitely work for any invited papers or overall review .
Author Response
The authors would like to thank this reviewer for his/her comments.
In response to the main comments raised by this reviewer: This is a review type of paper. It is intended to provide a comprehensive review of a large amount of work previously done by the authors. The paper is organized in a way that provides the reader with a lot of elements, including latest trends, in the field of ground moving target imaging.
Reviewer 3 Report
Main suggestions
It would be of great benefit to the readers if the authors would include a detailed description of the organization of the paper. Perhaps at the end of the into. In a separate section.
Due to the amount of symbols defined, it may be useful to also have a table of mathematical symbols.
In addition, the intro is missing a description of the contributions of this paper. Specifically, the authors should describe any novel aspects of this paper (theory, and/or experiments) as well as describe in detail what purpose this review serves.
Minor suggestions
- Line 21: ISAR is undefined in the first page.
- Line 22: "easier to detect that ground": that --> than
- L.29: PRF is used here before it is first defined.
- See the papers [1, 2] below, where in a fashion similar to SAR, motion is exploited to provide improved imaging resolution of hidden objects and scenes. The paper [1] exploits motion of occluders for improving resolution and sensoring noise, while [2] exploits the motion of controllable illumination to obtain high-resolution imaging through a small effective aperture.
- L.48, the acronym PRI is used here but is only defined on Page 11 (just before eq (25)).
- Just before equation (3), rotation is by angle \theta, however the rotation matrix M given in (3) depends on \alpha not \theta.
- Equation (4) is awkward to read because \sin and \cos functions are italicized (use \sin and \cos instead).
Same issue in (8). - Issue with y(k) in last line of page 4. I'm guessing this should be y^{(k)}
- Line 108: please define CPI
- Line 134: "An conversion" --> "Conversion"
- Not sure about Line 413 "QUI!!!"
Refs
[1] Saunders, C., Murray-Bruce, J., & Goyal, V. K. (2019). Computational periscopy with an ordinary digital camera. Nature, 565(7740), 472-475.
[2] Rapp, J., Saunders, C., Tachella, J., Murray-Bruce, J., Altmann, Y., Tourneret, J. Y., ... & Goyal, V. K. (2020). Seeing around corners with edge-resolved transient imaging. Nature communications, 11(1), 1-10.
Author Response
The authors would like to thank this reviewer for his/her comments.
It would be of great benefit to the readers if the authors would include a detailed description of the organization of the paper. Perhaps at the end of the into. In a separate section.
The introduction has been modified to provide a clearer motivation that pushed us towards writing this review paper. In additiona, and to address this reviewer’s comment, we have added a full description of the paper content (at the end of the introduction).
Due to the amount of symbols defined, it may be useful to also have a table of mathematical symbols.
This is a very good point and we acknowledge that it should have been introduced in the original paper. We have added a list of symbols (at the end of the paper, this may be moved to the beginning of the paper according to the editor’s style).
In addition, the intro is missing a description of the contributions of this paper. Specifically, the authors should describe any novel aspects of this paper (theory, and/or experiments) as well as describe in detail what purpose this review serves.
As mentioned earlier, we have completed the introduction with a motivation. This paper is a review paper and it does not introduce any novel algorithm. Nevertheless, merging together several concepts and results in a logical order into a single review paper provides a comprehensive view of the author’s approach to the problem of ground moving target imaging.
MINOR SUGGESTIONS
- Line 21: ISAR is undefined in the first page.
Corrected
- Line 22: "easier to detect that ground": that --> than
Corrected
- 29: PRF is used here before it is first defined.
Corrected
- See the papers [1, 2] below, where in a fashion similar to SAR, motion is exploited to provide improved imaging resolution of hidden objects and scenes. The paper [1] exploits motion of occluders for improving resolution and sensoring noise, while [2] exploits the motion of controllable illumination to obtain high-resolution imaging through a small effective aperture.
These two papers have been cited in the introduction
- 48, the acronym PRI is used here but is only defined on Page 11 (just before eq (25)).
Corrected
- Just before equation (3), rotation is by angle \theta, however the rotation matrix M given in (3) depends on \alpha not \theta.
Corrected
- Equation (4) is awkward to read because \sin and \cos functions are italicized (use \sin and \cos instead).
Same issue in (8).
Corrected
- Issue with y(k) in last line of page 4. I'm guessing this should be y^{(k)}
Corrected
- Line 108: please define CPI
Corrected
- Line 134: "An conversion" --> "Conversion"
Corrected
- Not sure about Line 413 "QUI!!!"
Corrected
Reviewer 4 Report
Dear authors,
I reviewed the paper entitled “Ground moving target imaging via SDAP-IFSAR processing: review and new trends” by Marco Martorella et al. This feature paper deals with a review of the techniques for ground moving target imaging involving space-time adaptive processing and inverse SAR, with the aim of producing a useful image of moving targets suppressing the ground clutter. The authors review the different techniques using single and multi-channel radar systems supported by a strong mathematical framework. In addition, they propose a novel approach based on Space-Doppler Adaptive Processing using virtual SDAP for making ground moving target imaging applicable to single-channel radar systems. They also review the cognitive SDAP algorithm and its advantages over the non-cognitive version.
The paper is in general well written with a correct English grammar and style. It seems to be written using British English so be careful with no mixing American and British English. There are some –ization –ized endings that should be changed by –isation –ised. You can check in the paper searching these words. There are several cases along the manuscript. In line 22 replace “that” with “than”.
The paper is well structured with a very detailed treatment of the theoretical aspects. No objections to the described formulation and description of the different systems and algorithms. The introduction section should indicate at its end a description of the goals of the paper and how is structured. It is very long and particularly I had to make a summary of the different sections to have a better idea of its contents and structure, so including this dissection of contents and the end of the introduction will help the reader to better follow the thread of the paper.
In line 21, add the meaning of ISAR as it is the first time it is introduced apart from the abstract.
Review equation numbers as in some places they appears as Eq. ? You can check searching through the manuscript. Also, in this version of the paper some changes were made that the order of equations was lost. If you read the text, it makes reference to an equation number that are not correct. Please, carefully review the manuscript and in special from page 28 on. In addition, also check in some parts where you make reference to subsection 3.3 which does no exits.
Check line 413. QUI!
There is also a mess with figure numbers. In this version of the manuscript some figures were missing from a previous version so the numbers in the text where they are called, are not correct. Check from page 15 on. For example, in page 15 you make reference to Fig. 9 and 10 and it should be 7 and 8.
Use IS units. Replace GHZ by GHz, KHz by kHz.
At the end of pag. 12, “Eq” is missing before (39). Also in line 309. In pag. 28 and 29 the number of equation is not between brackets.
In line 108, indicate the meaning of the acronym CPI
In Figure 2, indicate that the subplot b) is a zoom-in of subplot a)
In Figures 5 and 13, indicate the type of SAR system.
In Figure 9, indicate what every color box represents.
In Figure 11b, use the same colors as in 11a for the targets.
Enlarge Figure 18 a little bit.
Use an acronym for cognitive SDAP (C-SDAP) the first time it appears in the text (page 34?) and use it along the manuscript. Currently you introduced the acronym in the conclusions.
Author Response
The authors would like to thank this reviewer for his/her comments.
We have made sure that only British English words are used throughout the paper.
The paper is well structured with a very detailed treatment of the theoretical aspects. No objections to the described formulation and description of the different systems and algorithms. The introduction section should indicate at its end a description of the goals of the paper and how is structured. It is very long and particularly I had to make a summary of the different sections to have a better idea of its contents and structure, so including this dissection of contents and the end of the introduction will help the reader to better follow the thread of the paper.
We have modified the introduction by adding a clearer motivation for writing this paper and highlighted its intended contribution. Also we have added a description of the paper contents at the end of it, as suggested by this reviewer
In line 21, add the meaning of ISAR as it is the first time it is introduced apart from the abstract.
Done
Review equation numbers as in some places they appears as Eq. ? You can check searching through the manuscript. Also, in this version of the paper some changes were made that the order of equations was lost. If you read the text, it makes reference to an equation number that are not correct. Please, carefully review the manuscript and in special from page 28 on. In addition, also check in some parts where you make reference to subsection 3.3 which does no exits.
Done
Check line 413. QUI!
Removed
There is also a mess with figure numbers. In this version of the manuscript some figures were missing from a previous version so the numbers in the text where they are called, are not correct. Check from page 15 on. For example, in page 15 you make reference to Fig. 9 and 10 and it should be 7 and 8.
Corrected
Use IS units. Replace GHZ by GHz, KHz by kHz.
Corrected
At the end of pag. 12, “Eq” is missing before (39). Also in line 309. In pag. 28 and 29 the number of equation is not between brackets.
Corrected
In line 108, indicate the meaning of the acronym CPI
Corrected
In Figure 2, indicate that the subplot b) is a zoom-in of subplot a)
Corrected
In Figures 5 and 13, indicate the type of SAR system.
It is a generic side-looking multi-channel SAR systems. Both captions modified.
In Figure 9, indicate what every color box represents.
Corrected
In Figure 11b, use the same colors as in 11a for the targets.
This figure has been regenerated with the same colorsEnlarge Figure 18 a little bit.
Done
Use an acronym for cognitive SDAP (C-SDAP) the first time it appears in the text (page 34?) and use it along the manuscript. Currently you introduced the acronym in the conclusions.
Nice suggestion. We have implemented it. Thanks.
Reviewer 5 Report
Title:
Ground Moving Target Imaging via SDAP-ISAR processing: Review and New Trends
General description:
In the present work, the latest results of theoretical and practical meaning in the domain of ground moving target imaging with joint application of Space-Time Adaptive Processing and Inverse Synthetic Aperture Radar Imaging are discussed. The article is well written and organized. The ground moving target imaging problems are solved with application of different radar instruments and technologies. The article discloses the huge experience of the authors in matter.
Remarks:
Row 413: There is a word in Italian qui (hear). Remove this word. It is not necessary.
Rows 102-103: in the expression (16) 2D is not defined, and the expression is not correct as it is written.
In expression “SDAP processing”, the word “processing” appears twice.
In expression (2) the frequency f is clearly defined, whereas in (16, 18, 19, …) is not. Define lambda as lambda = c/frequency.
The article must be read carefully and remove some mistakes of that kind.
An interesting approach for SAR ground moving target imaging with inverse SAR scenario is suggested in:
A. D. Lazarov. Ch. Minchev. SAR Imaging of a Moving Target, Recent Advances in Space Technologies RAST 2007, Istanbul, Turkey, 14-16 June, 2007, pp. 366-372.
I would like to recommend the authors to cite the aforementioned article.
Author Response
The authors would like to thank this reviewer for his/her useful suggestions and comments.
Row 413: There is a word in Italian qui (hear). Remove this word. It is not necessary.
Removed
Rows 102-103: in the expression (16) 2D is not defined, and the expression is not correct as it is written.
We have defined the meaning of 2D- and corrected the sentence with 2D Inverse Fourier Transform as the formula indicates continuous variables and not discrete ones. 2D-IFFT is actually implemented in ISAR processors once the signal is digitized.
In expression “SDAP processing”, the word “processing” appears twice.
“processing” removed
In expression (2) the frequency f is clearly defined, whereas in (16, 18, 19, …) is not. Define lambda as lambda = c/frequency.
Done
The article must be read carefully and remove some mistakes of that kind.
We have checked the entire paper.
An interesting approach for SAR ground moving target imaging with inverse SAR scenario is suggested in:
A. D. Lazarov. Ch. Minchev. SAR Imaging of a Moving Target, Recent Advances in Space Technologies RAST 2007, Istanbul, Turkey, 14-16 June, 2007, pp. 366-372.
We have cited this paper in the introduction.
Round 2
Reviewer 3 Report
Suggestions have been appropriately addressed by the authors.
