Comparison of Forest Inventory Methods at Plot-Level between a Backpack Personal Laser Scanning (BPLS) and Conventional Equipment in Jeju Island, South Korea

Round 1

Reviewer 1 Report

Dear Authors,

I have finished my review on your manuscript. The attempt is interesting and could enhance our knowledge on the topic. However, there are many inconsistencies and points to be addressed before a potential publication. Please refer to my specific comments in the following.

Best regards,

R.

 

Title: needs some improvement to lose some of the particularity such as the location. Results of the international studies need to have a wider applicability.

Abstract: the background is too narrowly given and the justification of the study is missing. Font type needs to be carefully checked. It should be checked and corrected also to remove or explain the abbreviations given and to clarify what a “pattern” is. Not clear what the time includes and the term “approximately” is usually associated to a single figure. Otherwise it is a range.

Keywords: break them in less words.

 

Introduction

First sentence: the authors need to be careful here. The data is not rudimentary by any means, while the inventories would benefit from continuously collected data to be able to detect dynamics.

Second sentence: what is major?

S4: find a synonym for “garnering”

S5: maybe the authors could explain how the traditional methods are invasive…

Approximately 300-2 mil. >>> see the above comments

There is also a lack of proper software for high-den-sity point cloud processing >>> Check PointCloud

SLAM is rather a concept and not a technology

In my opinion the current version of the Introduction is rather a history and description of the existing scanning technology and procedures, failing to give the reader an insight to the importance of the problem pursued by the authors. What are the limitations we have and could be solved by your approach? What is the reason for your study? Answers to these questions should be proeminet in your introduction.

 

Materials and methods

Enhance figure 1 to help the reader understand it.

2.1 says about location but nothing about the materials and in my opinion it could be improved by adding more descriptive data.

Table 1: how was the wind speed measured?

2.3.1. Needs to be rephrased for clarity. Add a table to explain the elemental time consumption and to compare the two approaches in terms of work tasks.

Table 5 adds no relevant information. One could state in a sentence that all the trees from all the plots were detected, as you did in the following sentence.

Following sentences: that’s why you need a more detailed description of the forests. Would your approach work on a forest showing a well-developed understory, shrubs and seedlings. The statements that follow are purely comparative and add no value to your discussion. They should be merged in one sentence explaining the performance metrics and conditions related to your findings.

Methods are insufficiently described to allow repeatability…

Results and discussion

3.2. ????? What Tables?

A stand is more of an oval shape than a circle >>> what is a stand?

Although the value using BPLS is undervalued in the field survey value, the RMSE in the range of 1.223 to -1.401 cm is negligible in the forest man-agement plan, which rounds off at 2 cm, the NFI(National Forest Inventory) rounds off at 1 cm. >>> but it is important. Otherwise we could use the traditional way.

Discussion that follows has the same problems as above.

Table 8. The amount of the spent by pattern, and the number of point clouds. >>> amount of what?

pattern 5 had the longest distance of 9.2 m/min >>> distance is measured in meters. Speed is measured in m/min.

the scan time using ground ra-dars was 130–200 min/ha >>> time is measured in minutes. Efficiency could be measured in min/ha

Conclusions

Seem to be excessively long. First couple of sentences of the second paragraph are purely results and not conclusions.

Author Response

We appreciate your review of our manuscript. Prepared are responses and a revised manuscript in accordance with these comments. Revisions to our manuscript are indicated in red font. Please refer to the line number.

please refer to the attachment for our responses.

Respectfully,

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors present usage of BPLS in forest conditions for the sample plot inventory. The general idea is clear and can be valuable because such devices are not commonly used in forest practice. However, in the text, I found many errors and misunderstands which should be cleared. Most of my comments are presented below. I also put some final conclusions to the end of the review. I want to emphasise that I’m not perfect in English so please consider to send this text to native spear after corrections because in my opinion it must be improved.

Detailed comments:

1. What does it mean „artificial forest”. The definition is a little bit confusing.
2. Change the format of the location to N 33° 23’ 31.8″, E 126° 40′ 17.8” in this way you can easy paste it in maps Google.
3. Figure 1 should be improved. In the corner of the map put the location map with the Korean Peninsula with the extend rectangle of the area of interest. Put the names of seas. On the main map, the background map should be added because there is nothing now. I do not understand the line which dived the island into two parts. Think about some Open Street map background or Corrine land covers layers, hillside map or something because now it completely not clear.I would suggest to put also additional map with detailed plot locations. It could help to understand the amount of filed work.
4. Table 1 should be the number of trees – I think so
5. Table 1. Correct the units. I think it should be in [] and spaced from the name.
6. The wind speed value is really strange for me because the differences are very small and I do not consider this parameter as important. I would suggest putting the information about wind conditions in the text. By the way, you do not consider this parameter in conclusions.
7. Table 2. You repeat the Number of trees – it was in table 1. I would consider combining table 1 and 2.
8. “group of three researchers” I do not understand what is this number. Better to focus on how many people were necessary for BPLS and how many for classic surveying. In the chapter 2.3.2. many senates start with the “each” word. Definitely my English is far away from perfect but in my opinion this chapter is hard to read.
9. “The indoor tasks using a BPLS are defined as the following “ why there is a black dot at the beginning of this sentence?
10. 2.4. Statistic Test – in this chapter there is no statistic tests. The statistic test can be for example Wilcoxon-Mann-Whitney test, ANOVA, sample t-test etc. This chapter is completely not informative. I do not understand it at all. What measure stays for X? Why there is not detail description for every of x used in the equations?
11. Table 6 and 7 – is it needed to write “pattern” so many times? Are you absolutely sure you want to present the accuracy of DBH expressed in one-thousandth of a centimetre? This is a crazy small value. Did you measure the reference with this same scale?
12. “As for estimating height, the LS methods are less accurate” what LS stays for? I know Laser Scanning but it should be explained.
13. To be honest, comparing the results of BPLS to standard field measurements is a bad idea. If you want to be correct you have to cut the tree or use ALS data as a reference. Otherwise, your results are not reliable.
14. I do not know how the height was asses from BPLS
15. Figure 4 – it is not stem extraction but tree extraction. Generally, I think that nadir view of the point cloud would be more interesting. This could present the possibility of assessing the crown size which is important. By the way, for me, the good idea would be to make orthomosaic from UAV for your plots in order to compare the scanning results with reality.
16. “Table 8. The amount of the spent” - the amount of what?
17. Table 8 should be reconstructed. What for is the Area column? You cannot present the time in decimal values! Does such a big accuracy of values tell me something more? In my opinion not. I do not understand the last two columns. What do they represent?
18. Why the number of plots in table 9 are different for the Field survey and BLSP? Again remove area.
19. Definitely, you cannot tell researches around the world that when they want to measure 1 ha of the forest with the BPLS they will spend 162 and a half minute  Please try to be more general in your conclusions a specially in this matter because the amount of time is very sensitive considering the forest conditions or even the wheatear conditions. Now in my country we have half a metre of snow – so what will be the time in that case?
20. The figure 5 should be improved. Looks unclear and unprofessional.
21. Generally, the number of decimal places in your research is impressive. Please reduce it to the values which are really needed in the forest inventory.
22. “we showed that work ac-curacy or efficiency may vary depending on other LiDAR equipment and computer specifications” where did you show it?

There is no doubt that BPLS is the future of accurate sample plot inventory. However, as you mentioned in the text, it is very expensive and in my opinion, only reach countries can use it in the field. The thousands of researches proved that ALS is the most efficient and accurate data source for assessing the forest resources. Of course, it needs calibration base on the sample plots but I’m not sure that BPLS will be commonly used in that price. The potential BPLS reseller must offer the ready to use app for assessing the parameters. Lidar360 is not the solution.

In this research, I fell lack the parameters which can be extracted from the point could comparing to classic measurements. You do not mention at all about trees locations on the sample plot – we should remember that measuring tree location by the classic filed methods is not accurate. You should mention that BPLS is valuable because you can record the state of the forest in time and you can return to this after many years. This is not possible with raw values stored in Excel. Generally, I think this is valuable and interesting work but it should be improved and compared also with other reference data a specially height of the trees. Most of the errors are not big and can be easily improved.

I wish you good luck and I’m jealous you have so sophisticated equipment :-)

 

 

Author Response

We appreciate your review of our manuscript. Prepared are responses and a revised manuscript in accordance with these comments. Revisions to our manuscript are indicated in red font. Please refer to the line number.

please refer to the attachment for our responses.

Respectfully,

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors,

Thank you for this improved version of the manuscript.

I have found it much better written. However, I would suggest an additional English check of the manuscript as well as some corrections to some minor issues I have found.

For instance,

Section 2.3.1. Title needs to begin with a capital letter.

Lines 175-177: point cloud & value of x, y, z >>> needs rephrasing since a point cloud refers to a set of point having such values.

Line 176: by the delta>>>please improve this.

Line 183: The office works>>>work in the office phase or work at the office consisted of...

Table 7 & 8: consuming time >>> time consumption; survey process efficiency & survey coverage... >>> just state "Efficiency as the (first column) distance covered per minute and )second column) the area covered per minute

L289: Consuming the time>>>time consumption

Line 290: was approximately >>> was between

Line 294: travel distances >>> distances traveled (also in the rest of the text)

Line 303: approximately >>> in between.

Author Response

Thank you for reviewing my thesis.

 

My thesis has improved a lot because of the good comments.

Fixed additional modifications requested by Reviewer.

The modified content was displayed using the "Track Changes" function in Microsoft Word.

Thank you.

 

Respectfully,

Author Response File: Author Response.docx

Reviewer 2 Report

I read your text and it is improved. However:

• The tables should be better organized.
• Remove the space before the degree sign in the location latitude and longitude.
• You omit some of my comments. Maybe it is not important so much. I do not know.

I wish you good luck.

Author Response

Reviewer 2.

 

Thank you for reviewing my thesis.

 

My thesis has improved a lot because of the good comments.

Fixed additional modifications requested by Reviewer.

The modified content was displayed using the "Track Changes" function in Microsoft Word.

Thank you.

 

Respectfully,

Author Response File: Author Response.docx