Estimating Plant Pasture Biomass and Quality from UAV Imaging across Queensland’s Rangelands

Round 1

Reviewer 1 Report

The manuscript is well-written, it is apparent (and appreciated) that the authors put a lot of effort in preparing this document. 

Here are my notes:

Lines 51, 52, 53, 54, 55 and throughout the manuscript: I think it is best to use the #) notation instead of #. This clearly defines the author is listing items inline and is less likely to be confused with a period at the end of a sentence.

Line 262-263: The coefficient of determination, R2, ...

Figure 5: I suggest increasing the label font size and the graticule font size for easier reading; green/red/yellow is a difficult color scheme for many to interpret, I suggest the authors use different symbols for the three classes of quadrat locations as well as color. Are the plot labels even necessary? If not, remove them.

Figure 6: panel labels a and b are cut off but this might just be an artifact on my computer; increase font sizes of graticule labels and plot labels (are the plot labels even necessary in panels c and d?); increase symbol size and/or change symbol color for easier reading. Use another image for panel a, the glare present on the existing one is distracting.

Author Response

 "Please see the attachment."

Author Response File: Author Response.pdf

Reviewer 2 Report

This study builds on recent advances in UAV technologies and develops and tests an interesting method of mapping and monitoring pasture resources in large and diverse areas of Queensland, Australia.

From my point of view, all components of the article are well thought out, technically detailed and comprehensively presented to the readers.

I am impressed by the courage and perseverance in finding the novelty compared to the many results already published for UAV technologies for mapping for different purposes, even in pasture.

Your technical way to develop an accurate and spatially explicit measure of pasture biomass and nutrient composition that can be used both for satellite image escalation for long-term monitoring of large-scale pasture resources and for small scale measurement to improve land management of pasture resources is to be appreciated.

Every step of your study is detailed and technically consistent with both positive results and their challenges.

I have no negative comments or suggestions for your article!

Author Response

 "Please see the attachment."

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper content is aligned with AgriEngineering. The authors investigated the use of UAV-based method to estimate biomass and nutrient status. The methodology is not new, but the application is relevant. The thematic in the study area is underexplored. My main concern is regarding the non-reproducibility of the method. In general, it is not clear, and information in certain sections are missing.

Improvements in the manuscript are suggested as follows:

The abstract does not reflect the paper content. Nothing related to the used sensors was mentioned in the abstract. Machine learning methods were also used.

The first part of the abstract is very repetitive. Please, review it.

In the title,  it is used “quality” and in the abstract “nutrient”. I suggest standardizing in the text. The same with “drone”, “UAV” and “RPA”.

Lines 67-80: Why is it important to discuss the integration between UAV and satellite data? It was not adopted in the current work.

LiDAR instead of Lidar.

SfM is not a passive method. It is based on a passive sensor. Please, review it.

Only at the end of the introduction, I discovered that hyperspectral data was used. This was not mentioned in the abstract.

Hyperspectral is not a low-cost camera; however, for nutrient estimation is necessary. You can use this as motivation. Your work investigated the estimation of biomass and nutrients simultaneously.

Please, increase the font of Figure 1.

I discovered now (in section 2.3.1) that RGB images were also used. It was not mentioned previously.

Review the use of software and program: “Pix4D commercial software  [30] program”.

Only one flight in the nineteen plots was conducted? Please, inform the dates.

Lines 201-202: Why the maximum height was used?

Figure 2: Correct “independant”.

Why did RANSAC was used to estimate the biomass? To estimate biomass, in general, a simple linear regression is used. I suggest a comparison between your results with this common method.

Now, I verified that you presented the linear regression analysis in Figure 4. However, it was not mentioned in the previous section.

Section 3.1 does not present a relevant result. I suggest to include previously in the method section.

In the discussion section, it was mentioned that a “strong” correlation was achieved; however, I did not verify this in the results. 

Most of the conclusion brings future work.

Author Response

 "Please see the attachment."

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors performed most of the suggested corrections.