Measurements of the Thickness and Area of Thick Oil Slicks Using Ultrasonic and Image Processing Methods

Round 1

Reviewer 1 Report

The observation of oil spill quantity and oil film thickness has always been the focus of remote sensing oil spill monitoring. In this article, a method was proposed to access the volume of oil slick by simultaneously obtaining the thick oil slick thickness and area using ultrasonic inspection and imaging processing methods, respectively.The oil slick thickness was obtained by multiplying the speed of sound with the ultrasonic traveling time within oil slick, which was calculated using the cross-correlation method. The images of oil slick were captured by an optical camera using an airborne drone.The average oil slick volume was less than 10% higher than the added oil, a result which demonstrates the high measurement accuracy of the proposed method. The proposed method has been experimentally verified for accurately measuring the thickness, the area and the volume of oil slick in the laboratory experiments. This is an interesting experiment.

Suggestion:

1.The second section is about materials and methods. The oil types and steps of the experiment are explained here.

2.The area of oil slick was changed by the driving force generated by a water pump which was placed at the bottom of the tank to pump water up to the surface to make the surface water flow.However, the experiment is outdoors, the influence of temperature and wind field should be considered.

3.The crude oil with the density around 0.89 g/ml will emulsify.Emulsification will increase the thickness, volume and tension of the oil film, which will affect the experimental results.The time of the experiment also affects the emulsification.

4.The calculated volume of oil slick was nearly synchronizing increasing/decreasing with the measured thickness when the pump was alternatively turned on/off, a result which implies that the volume measurement is more dependent on the thickness measurement than the area measurement. This is because the area of the tank is fixed during the experiment.

This is not the case in real sea conditions.

5.It is not clear which remote sensing observation or multi-means oil spill observation the author designed this experiment to serve.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors,

In chapter 2. "Methodology" it is necessary to explain how this proposed method is different than the cited ones and what was the motivation for this work (hypothesis is missing, motivation for conducted research). The novelty of the proposed method needs to be explained in more detail and validate it with previous research and established models. In the Conclusion the future research should be described.

Sincerely,

Reviewer

Moderate editing of English language is needed. 

Author Response

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Reviewer 3 Report

General assessment:

In this study, the volume of oil slick is calculated by multiplying the thick oil slick thickness, observed using the ultrasonic immersion transducers installed in a ROV, by the oil slick area, observed using the optical camera installed in an airborne drone. The volume of oil slick is obtained by the observations above and below the sea surface, it is interesting. I think the manuscript is suitable for Remote Sensing, but there are several aspects to be improved.

Comments:

(1) The thick oil slick thickness and the oil slick area are observed using two different instruments from different sides of the oil slick at sea surface. Is it possible to simultaneously observe the thick oil slick thickness and the oil slick area in one instrument? For example, only use drone or only use ROV.

(2) As shown in the manuscript, only one ROV was used and only the oil slick thickness at one point was observed, which will cause large observation errors. If possible, please use several ROVs to observe the oil slick thickness.

(3) In Line 2 of Page 10, the RGB thresholds were set as (60, 60, 60). Is this threshold fixed or changed with the environments? When the method is used in the actual case of oil spill accident, how to set this threshold?

(4) What is the difference between this study and Du et al. (2023, IEEE Trans. Instrum. Meas)? Is the measurement of the oil slick thickness using ROV in this study the same as Du et al. (2023)?

(5) All the numbers of the references in the text of manuscript are strange. It should be [number].

Author Response

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Reviewer 4 Report

the abstract effectively summarizes the key aspects of the proposed method, highlighting its potential significance in addressing the challenges of oil spill response and volume estimation.

The author has done a comprehensive job in addressing the key aspects of the topic, providing relevant background information, and outlining the proposed method for measuring oil slick thickness and area. The abstract effectively highlights the importance of this measurement for oil spill response strategies and evaluating disposal efficiency. The inclusion of a Remotely Operative Vehicle (ROV) and the use of ultrasonic inspection and imaging processing methods demonstrate the practical implementation of the proposed method. The paper mentions the verification of the method through laboratory experiments, showcasing its accuracy. Overall, the paper is well-structured, concise, and provides a clear overview of the proposed method's potential applicability.

English is undderstandable.

Author Response

Thanks for your comments. The English was carefully edited and revision was marked in yellow.