Vessel Target Echo Characteristics and Motion Compensation for Shipborne HFSWR under Non-Uniform Linear Motion

Round 1

Reviewer 1 Report

In this paper, the authors discuss the characteristics of target echo spectrum and motion compensation methods for shipborne HFSWR. In general, the topic in this paper is very interesting. However, the methods are not comprehensively validated. More details should be presented to further validate presented method.

 

1. The system shown in Fig. 1 is used as the transmitting and receiving stations. However, the target and ship move continuously. At this point, the reviewer wanders to know whether the authors consider this influence. Do the authors consider the stop-and-go assumption on performance? If this is not considered, the authors should clarify the reason. It is better to use simulations to clarify this comment.

 

2. The symbol ‘j’ cannot be found in the exponential term of Eq. (2). The authors should delete s(t) in square brackets of Eq(4). Similar issues are often occurred in this paper. The authors should check the whole paper to avoid these errors.

 

3. From Fig. 3, the authors just consider the yaw. However, the ship often suffers from six types of motion errors, namely surge, sway, heave, roll, pitch, and yaw errors. Why do the authors just consider the yaw? Do the remaining motion errors slightly affect the performance?

 

4. Line 274: t0 -> t_0. Here, ‘0’ is a subscript symbol.

 

5. Line 272: the authors should clearly clarify how to obtain the spindle angle?

 

6. In section 5, the authors should present processing result corresponding to each motion compensation step. With this operation, the readers can easily understand the authors’ work. Besides, the readers can find which compensation step is the dominant factor for the performance improvement.

 

7. Is the unit in colorbar of Fig. 12 dB? The authors should clearly present this unit. Similar issues should also be checked in this paper.

 

8. In Fig. 13, the authors just present the results when the ship velocity is 10 knots. In order to strongly validate the authors’ method, the authors should discuss the results when the ship works with other velocity.

 

9. In Fig. 15, the authors show the compensation results. However, the readers cannot find the yaw error. At this point, the authors should clearly present the yaw error, as the yaw error is a known parameter for simulations.

 

10. Based on Fig. 26 and Fig. 27, the improvement introduced by authors’ method is somehow slight. This is not consistent to the conclusions drawn from simulations. The authors should check their data. Besides, the authors should present the ship heading and velocity.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This paper analyzes the influence of ship motion on the echo of a high-frequency surface wave radar (HFSWR) installed on a moving ship as well as on its target detection performance. When the ship velocity and yaw angle change periodically, false target echo peaks will appear in the echo spectrum, which will reduce the accuracy of target detection. To overcome this problem the authors propose a motion compensation method  that includes the heading compensation for the effect of yaw and the velocity compensation for non-uniform movement. This method is presented in a clear and mathematically consistent way in the paper. This paper has a satisfactory scientific contribution because the experimental validation of the proposed method with measured shipborne HFSWR data was performed. In order to further improve the quality of work, the authors are suggested the following:

• It is necessary to describe in more detail the hardware-software environment in which the simulations were conducted and in which the results of the simulations presented in the paper were obtained.
• It is necessary to eliminate the shortcomings in the graphical presentation of the results in order to enable a clearer interpretation of the results (In Fig. 18 and Fig. 20, the authors did not indicate which results correspond to the situation before motion compensation and which results correspond to the situation after motion compensation. In Figs 6a, 7a, 8a and 9a the variable label on the x-axis is missing).

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The work in this manuscript appears scientifically sound.  However, there are extensive changes that must be made to the English spelling and grammar, in addition to some technical questions and issues which are given in the attached and annotated PDF file, before this work can be considered for publication. 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I have carefully read the whole paper compresensively. The authors well addressed my comments. Therefore, the reviewer suggests that this paper is accepted.

Reviewer 3 Report

I have not seen the fully-revised paper, however based on the response to reviewer reports, I believe that my comments have been addressed and that the manuscript has been sufficiently improved to warrant publication in Remote Sensing.