Water and Vegetation as a Source of UAV Forest Road Cross-Section Survey Error

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The document to be evaluated deals with an important aspect of forest management, namely the methods for collecting data on the technical condition of the forest road infrastructure. At a time when manpower is scarce, the search for efficient and, above all, effective, largely automated solutions is of particular importance. Only with up-to-date and truthful inventory data can the forest manager plan and implement suitable and rational management measures.

I find that the prepared article is thorough, clear and factual and meets the standards of a scientific text. However, to make it more meaningful, I would suggest including the following comments:

• “Abstract” should be expanded to include the main conclusions of the research conducted – only the results are mentioned;
• ensure that the abbreviations used in the text are explained for the first time, including those that we consider common knowledge, also in the figures, which makes the text easier to understand for those who have little to do with the research methods used;
• in the first part "Introduction" emphasize that the forest manager must have up-to-date information on the technical condition of the road infrastructure, including for the purposes of rescue and firefighting operations;
• the description of the survey section, the research conditions would be worth supplementing with some photos, especially if such photos are available to the authors;
• line 128-130 (“The coordinates of the points for georeferencing the total station were determined using a GNSS device in RTK mode according to the instructions explained in Mihelič et al. [50]”): Information about the GNSS device used (Stonex S900A?) should already be given here;
• it is advisable to complete the information on the characteristics of the forest near the surveyed road: tree stand structure, deciduous/evergreen broadleaf species, height, canopy closure and others;
• it would be advisable to add information about the surveying conditions: the tachymetric survey was carried out in February 2024, let's assume there was no snow or ice cover (?), what about dead vegetation? None, just bare ground?
• it is advisable to complete the information: type of road surface, slope gradient – the data can be entered on prepared drawings, how the height of the vegetation cover was determined – the drawing shows that this was not the maximum height;
• it can be seen that the measurement errors in spring were influenced by the tree canopy cover; what were the parameters of the vertical road clearance and could its proper maintenance significantly improve the quality of the measurement results in the cross-section?
• the available results of the statistical analyzes assume the normality of the distribution of the investigated variables; were the appropriate tests performed?
• with the knowledge and experience of the authors, it is worth expanding the conclusions with suggestions for the direction of further research.

Finally, I would like to congratulate the Authors on the important research topic that you have undertaken and to point out that it was a real pleasure to read the fruits of Your labor.

Author Response

First, we would like to thank the reviewer for the comments that will certainly make this article better. We appreciate the time and knowledge invested in reviewing our article.

 

Comment 1:

• “Abstract” should be expanded to include the main conclusions of the research conducted – only the results are mentioned.

Authors response: Thank you for your comment. We added most important conclusions in Abstract.

Comment 2:

• Ensure that the abbreviations used in the text are explained for the first time, including those that we consider common knowledge, also in the figures, which makes the text easier to understand for those who have little to do with the research methods used;

Authors response: Thank you for your comment. We added abbreviation explanations for all abbreviations in text. For the pictures, as we believe abbreviations are explained good in text, so we didn’t add explanations in captions or pictures.

Comment 3:

• in the first part "Introduction" emphasize that the forest manager must have up-to-date information on the technical condition of the road infrastructure, including for the purposes of rescue and firefighting operations;

Authors response: Thank you for your comment. We added additional line in Introduction.

Comment 4:

• the description of the survey section, the research conditions would be worth supplementing with some photos, especially if such photos are available to the authors;

Authors response: Thank you for your comment. As the other reviewer requested less graphic in article, we didn’t add photos of research conditions.

Comment 5:

• line 128-130 (“The coordinates of the points for georeferencing the total station were determined using a GNSS device in RTK mode according to the instructions explained in Mihelič et al. [50]”): Information about the GNSS device used (Stonex S900A?) should already be given here;

Authors response: Thank you for your comment. Corrected.

Comment 6:

• it is advisable to complete the information on the characteristics of the forest near the surveyed road: tree stand structure, deciduous/evergreen broadleaf species, height, canopy closure and others;

Authors response: Thank you for your comment. We added additional information about research area.

 

Comment 7:

• it would be advisable to add information about the surveying conditions: the tachymetric survey was carried out in February 2024, let's assume there was no snow or ice cover (?), what about dead vegetation? None, just bare ground?

Authors response: Thank you for your comment. We added additional information about research conditions.

Comment 8:

• it is advisable to complete the information: type of road surface, slope gradient – the data can be entered on prepared drawings, how the height of the vegetation cover was determined – the drawing shows that this was not the maximum height;

Authors response: Thank you for your comment. We added additional information.

Comment 9:

• it can be seen that the measurement errors in spring were influenced by the tree canopy cover; what were the parameters of the vertical road clearance, and could its proper maintenance significantly improve the quality of the measurement results in the cross-section?

Authors response: Thank you for your comment. We added information on vertical road clearance. We believe that with branch cutting, quality of the measurement for furthest cross section points would increase. One can question is it necessary to do this kind of maintenance as those branches don’t go over forest road and don’t affect trafficability as forest road clear area is very wide (horizontal 30m, vertically min 15 m).

Comment 10:

• the available results of the statistical analyzes assume the normality of the distribution of the investigated variables; were the appropriate tests performed?

Authors response: Thank you for your comment. Kolmogorov-Smirnov and Shapiro – Wilk test showed that data is normally distributed.

Comment 11:

• with the knowledge and experience of the authors, it is worth expanding the conclusions with suggestions for the direction of further research.

Authors response: Thank you for your comment. We added suggestions for the further research in conclusions

Comment 12:

Finally, I would like to congratulate the Authors on the important research topic that you have undertaken and to point out that it was a real pleasure to read the fruits of Your labor.

Authors response: Thank you for your kind comment and contribution to this article!

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Reviewer's Notes

1. The authors write (lines 82-83) "Furthermore, it is necessary to establish a fast and reliable survey method for the forest road cross section..." but nowhere in the introduction or other chapters of the article (results, discussion) do they present a description and analysis of the time required to process the photos from the raid. Only the time taken to take the photos is given (line 143). Since the conclusions refer to this (lines 365 and 401), it requires supplementation.
2. 92 cross-sections were assumed and according to Fig. 2 each had 13 measurement points, which gives a total of 1196 field points, but 1108 were given (line 132).
3. The description of the studied section does not include any information about the tree stand (species, age, etc.) or how far it is from the road. This is very important for taking photos at a height of 60 m. If the ditches were analyzed, why weren't flights made at a lower level between the tree stand (road strip)?
4. Fragments of text that describe the equipment (even the computer) in great detail are unnecessary because they contribute nothing substantive to the content of the article (e.g. lines 148-151).
5. Some of the drawings can be removed without losing the value of the article, as well as table 1; Fig.1 - very general and does not show the specifics of the given road, Fig.3 - even when very enlarged it is illegible and it is not known what can be read from it.
6. Were the obtained results distributed close to normal, that parametric ANOVA tests were used? This requires explanation in the paper.
7. The discussion needs improvement. In many parts it is a repetition of results, e.g. lines 318-332.
8. The conclusions were written in a very descriptive manner, and there was no clear indication of what resulted from the authors' research. Some of the statements do not result from the analyses conducted by the Authors, nor from discussions in the literature (e.g. line 365) "Unmanned aerial vehicles enable fast and cheap measurement of cross-sections of forest roads, ..." and (line 401): ... RGB cameras offer many advantages and quick solutions for field surveys ...".
9. In the literature descriptions, in several cases there is no https://doi..., and e.g. in items 7, 19, 25, 28-30 and others, no access to these materials is provided.

 

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

First, we would like to thank the reviewer for the comments that will certainly make this article better. We appreciate the time and knowledge invested in reviewing our article.

Comment 1:

• The authors write (lines 82-83) "Furthermore, it is necessary to establish a fast and reliable survey method for the forest road cross section..." but nowhere in the introduction or other chapters of the article (results, discussion) do they present a description and analysis of the time required to process the photos from the raid. Only the time taken to take the photos is given (line 143). Since the conclusions refer to this (lines 365 and 401), it requires supplementation.

Authors response: Thank you for your comment. We added information about photogrammetry processing time in table 2, and time required for total station survey in Materials and Methods text section. 

Comment 2:

• 92 cross-sections were assumed and according to Fig. 2 each had 13 measurement points, which gives a total of 1196 field points, but 1108 were given (line 132).

Authors response: Thank you for your comment. A minimum of 11 points were recorded on each cross-section, while on some profiles, where sudden changes in the cross-section of the terrain were observed, more points were recorded to present the terrain as clearly as possible. We added this information in Materials and Methods. In Figure 2 only red dots are total station survey points. Blue points were measured with geodetic rod.

Comment 3:

• The description of the studied section does not include any information about the tree stand (species, age, etc.) or how far it is from the road. This is very important for taking photos at a height of 60 m. If the ditches were analyzed, why weren't flights made at a lower level between the tree stand (road strip)?

Authors response: Thank you for your comment. We added requested information. Even though horizontal clearance was 13 meters on each side of the road, tree branches were above side ditches in some areas of research area. That is the reason for 60 m UAV flight height. We agree that lower flight height would maybe increase accuracy, but it was not possible on this research site.

Comment 4:

• Fragments of text that describe the equipment (even the computer) in great detail are unnecessary because they contribute nothing substantive to the content of the article (e.g. lines 148-151).

Authors response: Thank you for your comment. We removed computer characteristic from text.

Comment 5:

• Some of the drawings can be removed without losing the value of the article, as well as table 1; Fig.1 - very general and does not show the specifics of the given road, Fig.3 - even when very enlarged it is illegible and it is not known what can be read from it.

Authors response: Thank you for your comment. We removed Figure 3. We believe that Table 1, which shows the specifications of the equipment used, can be useful for the reproducibility of the research and comparison of data obtained by other authors.

With Figure 1, we tried to emphasize the characteristics of the research area, the appearance of the road network of the lowland area and the challenge of UAV survey caused by this (straight, linear road). This can also be one of the future research topic, as some authors emphasize impact of GCP placement in UAV survey missions like this one. Also, we added additional information about forest road in Materials and Methods.

Comment 6:

• Were the obtained results distributed close to normal, that parametric ANOVA tests were used? This requires explanation in the paper.

Authors response: Thank you for your comment. Data was normally distributed, Kolmogorov-Smirnov and Shapiro – Wilk test were used. We added explanation in the paper.

Comment 7:

• The discussion needs improvement. In many parts it is a repetition of results, e.g. lines 318-332.

Authors response: Thank you for your comment we have tried to compress the results repetition between the lines 318-332 but other parts remain unchanged since after every stated result follows author's explanation and discussion regarding the reasons of the obtained results. We are kindly asking reviewer for additional explanation.

Comment 8:

• The conclusions were written in a very descriptive manner, and there was no clear indication of what resulted from the authors' research. Some of the statements do not result from the analyses conducted by the Authors, nor from discussions in the literature (e.g. line 365) "Unmanned aerial vehicles enable fast and cheap measurement of cross-sections of forest roads, ..." and (line 401): ... RGB cameras offer many advantages and quick solutions for field surveys ...".

Authors response: Thank you for your comment. We have corrected highlighted parts in the lines 365 and 401 to be more adapted to the results of the investigation, shortened the parts from lines 318-332 and added additional explanations to Conclusion (in the main document highlighted yellow). We disagree with the claim that there was no clear indication of what resulted from the authors' research so kindly asking reviewer for additional explanation.

Comment 9:

• In the literature descriptions, in several cases there is no https://doi..., and e.g. in items 7, 19, 25, 28-30 and others, no access to these materials is provided.

Authors response: Thank you for your comment. We checked literature. For some of the literature there is no DOI number available. We added links to sources. Everything should be available online, except number [7] and [23]. We can provide pdf scans if necessary. For one reference DOI number is not valid, but article can be found online.

 

*The article has been re-checked and proofread by an English professor.

 

Authors:  In the end, authors would like to thank Reviewer once again for time, knowledge and excellent comments, that undoubtedly improved this article.

Author Response File: Author Response.pdf