Limiting External Absorptivity of UAV-Based Uncooled Thermal Infrared Sensors Increases Water Temperature Measurement Accuracy

Round 1

Reviewer 1 Report

The authors designed an experiment to test the hypothesis that modifying the surface absorptivity of uncooled TIR sensors can reduce thermal drift by limiting absorptance and associated microbolometer heating. The paper is interesting for readers and the experimental results showed a good performance. It is recommended for acceptance in the current version.

Author Response

Thank you for your review. 

Many thanks, 

Antóin and Barret

Reviewer 2 Report

Thank you for the opportunity to review the manuscript titled “Limiting external absorptivity of UAV-based uncooled thermal infrared sensors increases water temperature measurement accuracy”. I enjoyed this paper and I think it is a valuable addition to the literature in this fast-evolving field.

The authors test three hypotheses:

·         Reduced surface absorptivity of uncooled microbolometers would limit thermal drift

·         Clear sky conditions would increase the signal-to-noise ratio of the microbolometer thereby limiting thermal drift, and

·         Increase in air temperature would lead to an increase in thermal drift.

The manuscript provides a brief review on the history of TIR technology and recommendations for increasing the accuracy of uncooled UAV-based TIR mapping.

Comments to the Author

General comments:

The manuscript is well written, easy to follow and well organized. One main suggestion is to add a flow chart to describe each step to be considered to minimize drift. For example, depending on light conditions at site (e.g., maybe shading from canyon or canopy); how many light sensors to deploy, what is an appropriate number of temperature loggers to capture enough variability of water temperature. Do you place temperature loggers near places where emissivity may be different (e.g., substrate of different of color)? This type of information would be useful for a practitioner.

Specific comments:

Abstract: font in second paragraph seems larger  

Lines 53-54: include spatial resolution here

Lines 57-58: mentions high resolution here (what ranges?)

Figures 1, 5 and 10: extra period at the end of caption

Line 344: I would say that both correlations are weak. The Rf sensor’s correlation, maybe moderate?

Lines 383-385: remove “that” from each of the hypotheses

Line 452: “This relationship was true for both sensors” I don’t agree that there is a relationship between light and sensor deviation for the D sensor with an R²=0.13  Is this significant? Maybe you can say there is a trend?

Line 487: I say that air temperature is moderately correlated with sensor deviation just for the R sensor.  I don’t see a strong relationship for the D sensor. That relationship seems to be driven mostly by one point. Same here as with light. The relationship for the D sensor doesn’t seem to be significant.

 

Author Response

First, thank you for taking time to review our paper.  Your comments have strengthened the paper, and we truly appreciate your time.

 

We provide responses to your comments in the attached .docx.  Our responses are in the blue font.

Best,

Antóin and Barret

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript titled "Limiting external absorptivity of UAV-based uncooled thermal infrared sensors increases water temperature measurement accuracy", submitted by O'Sullivan and Kurylyk is well within the scope of the Journal. This study proposes to alter the surface absorptivity of uncooled TIR to reduce Thermal drift.

The study is interesting. The literature review is quite comprehensive and up-to-date. Most of the figures are good. The rationale behind the different parts of the experiments is well explained. Authors can provide a methodology flowchart to explain the methodology. Another healthy aspect was the discussion on the limitation of the experiments. 

In my opinion, the manuscript lags behind in presenting data from a day when the overcast was there. Data similar to that of figure 9 can be present and make the case stronger for section 4.2

Authors can also use the following paper's help to strengthen their manuscript.

Mokhtari, A., Ahmadi, A., Daccache, A., & Drechsler, K. (2021). Actual evapotranspiration from UAV images: a multi-sensor data fusion approach. Remote Sensing, 13(12), 2315.

Mishra, P. K., & Rai, A. (2021). Role of unmanned aerial systems for natural resource management. Journal of the Indian Society of Remote Sensing, 49(3), 671-679.

In the Introduction part, Figure 1 is not properly cited. Figure 1 tells about cost comparison, and 1 (e) is about how the research has been increasing with the year. Lines 60 and 61, "In the last decade, UAV-based TIR sensors have become increasingly common in river research and applications" (Figure 1c) is referred to this line, whereas 1 e is the most suited one. In line 65, you can give reference to figure 1 because here, the authors have talked about the cost.

Figure 6 caption can mention the acquisition of the image, i.e. from which sensor have you acquired it.

In Figure 8 (d-f), what do numbers (1200, 1300, 1400, etc.) inside the panel represent?

SI units of length should be in small letters. (Fig 4, scale). Also, try to keep the scale magnitude as an integer.

 

Author Response

First, thank you for taking time to review our paper.  Your comments have strengthened the paper, and we truly appreciate your time.  

We provide our responses to your comments in the attached .docx.  Our responses are in blue font. 

Best,

Antóin and Barret

Author Response File: Author Response.docx

Reviewer 4 Report

The manuscript presents an interesting research about using UAV-based TIR sensors in a specific case study. The results discussed find application in a wide range of disciplines for monitoring several environments. Although the purpose of the study is clear, in some parts of the text the methodology and the results are not clearly discussed.

For details:

(1) In the opening sentence of the Introduction, in order to complete the initial overview of applications in other disciplines, the authors should cite at least two other works such as the followings:

Massaro, A.; Panarese, A.; Galiano, A. Technological Platform for Hydrogeological Risk Computation and Water Leakage Detection based on a Convolutional Neural Network. In Proceedings of the IEEE International Workshop on Metrology for Industry 4.0 & IoT (MetroInd4.0&IoT), Rome, Italy, 7–9 June 2021; pp. 225–230, doi: 10.1109/MetroInd4.0IoT51437.2021.9488561

Goddijn-Murphy, L.; Williamson, B.J.; McIlvenny, J.; Corradi, P. Using a UAV Thermal Infrared Camera for Monitoring Floating Marine Plastic Litter. Remote Sens. 2022, 14, 3179. https://doi.org/10.3390/rs14133179

(2) In the section "Methods", the authors are invited to improve the form of the text, especially in subsections “Flight plans and image processing” and “Statistical analyses”. In Table 1 the columns 'Height' and '# of images' are redundant; it is sufficient to report the respective values in the caption or in the text. The authors should briefly give some details on the statistical methods used or cite some papers that do so.

(3) In the "Results" section, authors should improve the quality of the presentation. In particular, it is necessary to better explain Figure 5(f), the content of Table 2 and the caption of Figure 8. It is advisable to define the quantities used (WDs, pDs, etc.) and possibly report the formulas used in the statistical analysis in order to simplify reading for the reader.

(4) All mathematical and physical parameters used should be defined. Instead, Ds and Rs are defined repeatedly throughout the various sections.

(5) There are two different sections called " Statistical analyses", please check.

Author Response

First, thank you for taking time to review our paper.  Your comments have strengthened the paper, and we truly appreciate your time.  

We provide our responses to your comments in the attached .docx.  Our responses are in blue font. 

Best,

Antóin and Barret

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

All my comments and suggestions have been addressed except for 1.

The figures need to be revised where measurement units are written. SI unit name should be in small letters. (Fig 4, scale). In this regard I would give the reference of Bureau Internationale des Poids et des Mesures' guidance, (https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf/fcf090b2-04e6-88cc-1149-c3e029ad8232) from the SI Brochure (PDF; see p. 148 for English) clause 5.3: 

"Unit names are normally printed in upright type and they are treated like ordinary nouns. In English, the names of units start with a lower-case letter (even when the symbol for the unit begins with a capital letter), except at the beginning of a sentence or in capitalized material such as a title"

 

Also, try to keep the scale magnitude as an integer. 

Author Response

We have revised the figures.

Many thanks for your review!

Antóin and Barret

Reviewer 4 Report

I believe the manuscript has been sufficiently improved.

Author Response

Many thanks for your review.

Antóin and Barret