Fusion of UAV Hyperspectral Imaging and LiDAR for the Early Detection of EAB Stress in Ash and a New EAB Detection Index—NDVI_(776,678)

Round 1

Reviewer 1 Report

Authors present a complete research study on fusion of UAV hyperspectral and LiDAR data for early detection of EAB stress on ash. In this study the sensitive wave band at 678 nm was identified and a new EAB detection index, NDVI(776,678), was created and evaluated. The improvement is obvious in comparing with other possibilities. This manuscript has been well written technically and in English expressions. The technical procedure is clear and the results and conclusion are convincing. I would suggest to accept it as is to let readers, especially from those doing similar area of research to benefit. Thanks!

Author Response

Dear Reviewer,

Thamks for your suggestion for minor editing of English language and style. The manuscript has been carefully reviewed by an experienced editor whose first language is English. Next are point by point responses to your comments.

Reviewer 2 Report

The research work "Fusion of UAV hyperspectral and LiDAR for early detection of EAB stress on ash and a new EAB detection index -NDVI(776,678)" does not make it easy to separate methods from results, and the methods are not well explained which makes it hard to understand the research topic.

The authors' topic "Fusion of UAV hyperspectral and LiDAR for early detection of EAB stress on ash and a new EAB detection index -NDVI(776,678)" is an interesting topic with respect to the use of state of the art remote sensing technologies and other equipment to measure the forest trees physiochemical parameters such as LAI and chlorophyll content. However, the manuscript is written in a way similar to a technical report than a normal research work the following remarks may help in fixing some of the major issues.

1- In the abstract no need for the sentence from lines 27 to 29

2-Keywords are very long reduce them, please

3- In the introduction try to add a small paragraph describing in general the dilemma of pests that attacks forests internationally and the damages that it causes and the methods to detect them and eliminate them.

4-support the sentences between 79 and 85 with references

5-What is the area size of the study area

6-In the methods section the authors mixed the methods and the results. They should separate them i.e. in subsection 3.3 describe Savitzky-Golay filter and PLS-VIP in more detail. The details about selecting the most sensitive bands should be in the experimental results.
The same applies to other sub-sections such as 3.4 where the authors calculated OA from the confusion matrix and the Mean Decrease Accuracy.

7- The authors indicated in subsection 3.4 how to select the highest and lowest sensitive bands for stress, but it is not clear how the authors obtained equation 1 and why it should be like the NDVI equation 

8-The comparison with other vegetation indices should be in the experimental results and not in sub-section 3.5

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript presents methods to fuse UAV hyperspectral and LiDAR imager for early detection of EAB stress on ash and a new EAB detection index -NDVI(776,678). The experimental site is in Beijing, the authors should discuss the pros and cons of transforming the technology and methodology to similar or different areas across the globe. There are several minor comments listed below. I would also suggest a thorough revision of the writing style. The article can be considered for publication in Remote Sensing after addressing the comments.

Line 10: Consider replacing “imported” with “exotic”

Fraxinus pennsylvanica Marsh (ash) or F. pennsylvanica or ash.  Should be consistent in use, especially in the abstract.

Line 19: Should elaborate on the stages.

Line 26-27, do you mean the accuracy decreased when combining different data sources?

Introduction: The introduction is very good; the authors demonstrate a thorough knowledge of the published literature and highlight the importance and background to carry out this investigation.

References for the climate data are missing in the study area.

Fig 1. Add a location map of the study area in a global context.

Line 129: How the SIF and LAI were measured? Which instruments were used?

Material and Methods: Methods are technically strong and well explained.

Results and Discussion. Results are presented well and discussed in detail.

Conclusion: NO Comment

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have fulfilled all the requested modifications by the reviewers except adding more information about the use of LIDAR and optical images for the enhancement of the information to be extracted.

• It is better if the authors can create a separate section for the state of the art (literature review)
• Authors are urged to add the following references in the introduction as how LIDAR and optical images are used to help in enhancing the extracted information such as forests and urban features.

A-Toward Robust Segmentation Results Based on Fusion Methods for Very High Resolution Optical Image and LiDAR Data, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 10,  N0.  5, Print ISSN: 1939-1404, Online ISSN: 2151-1535, DOI: 10.1109/JSTARS.2017.2653061, 2017.

B-How to combine lidar and very high resolution multispectral images for forest stand segmentation?, 2017 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 2017, pp. 2772-2775, doi: 10.1109/IGARSS.2017.8127572.

C-Combining LiDAR data and airborne imagery of very high resolution to improve aboveground biomass estimates in tropical dry forests, Forestry: An International Journal of Forest Research, Volume 92, Issue 5, October 2019, Pages 599–615

Author Response

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Author Response File: Author Response.pdf