Mapping Canopy Cover in African Dry Forests from the Combined Use of Sentinel-1 and Sentinel-2 Data: Application to Tanzania for the Year 2018

Round 1

Reviewer 1 Report

This manuscript addresses a challenging mapping problem and suggests much potential for utilization of multiple global sensors now online. I found the study to be well conceived and the manuscript to be clear and well written. 

I just have several minor comments to recommend improvements to the manuscript.

Line 340 - after indicating these components of the proposed legend, this brief reference to "testing" and and then not using them leaves the reader wondering why. Either expand on this explanation of perhaps remove reference to them in Table 2.

Line 508 - typo "...data cannot be handled.."

Line 533 - as the measurement of dry forest degradation is quite significant, some expansion on this discussion is warranted, so I encourage more discussion on how this methods might be combined with other methods for that objective. 

Author Response

This manuscript addresses a challenging mapping problem and suggests much potential for utilization of multiple global sensors now online. I found the study to be well conceived and the manuscript to be clear and well written. 

We thank the reviewer for his/her time reviewing our paper. We addressed the comments raised by the reviewer as detailed in our answers.

I just have several minor comments to recommend improvements to the manuscript.

Line 340 - after indicating these components of the proposed legend, this brief reference to "testing" and and then not using them leaves the reader wondering why. Either expand on this explanation of perhaps remove reference to them in Table 2.

We understand the comment, we removed the reference to the unused elements in Table 2

Line 508 - typo "...data cannot be handled.."

We thank the reviewer for spotting this typo

Line 533 - as the measurement of dry forest degradation is quite significant, some expansion on this discussion is warranted, so I encourage more discussion on how this methods might be combined with other methods for that objective. 

Regarding the monitoring of dry forest degradation, we have further developed this discussion point as suggested by the reviewer. Our aim is mainly to suggest that the resulting map of our study can be used as reference map (for year 2018) to monitor future degradation processes (post 2018) using appropriate approaches. Revised section reads as follows:

It is important to note that the maps in this study do not distinguish open natural forest from degraded ones (e.g. landscape where tall trees are removed). Forest degrada-tion is a process of changes within the forest which negatively affect the structure or func-tion of the stand or site, and thereby lower the capacity to supply products and/or services [65]. An exhaustive assessment of past degradation would need to be based on long time series of satellite imagery such as conducted in tropical moist forests [6]. Methods target-ing the monitoring of forest degradation and forest disturbances [19,66] could be used in combination with the forest cover maps presented in this study to assess and map forest degradation that happened in following years (i.e. post 2018).

Reviewer 2 Report

Dear Authors,

I have reviewed the paper "Mapping canopy cover in African dry forests from combined use of Sentinel-1 and Sentinel-2 data: application to Tanzania for year 2018". The aims of the paper are germane with Remote sensing applications topic, in this form of article fits with the international scientific standards. The paper is written with a moderate English level. The contribution of this paper to the scientific knowledge is good. Although, in my opinion, there some important flaws and I suggest the corrections in the  following comments.

Keywords: I suggest to avoid keywords already used in the title, moreover remove the comma after “machine learning”

Reference formatting to be corrected according to the journal’s guidelines

Line 49-50: add references for these challenges

Lines 97-113: this part of the section is clear and the written concepts are very meaningful and important, however the link between the need of developing more user-friendly procedures for remote sensing of forests and the aim of your study is not clear, in which way this manuscript and the followed approach is answering to the need of making remote sensing monitoring user-friendly?

Discussion section: I think authors should highlight in a clear way for the readers what are their innovative findings and most of all the advantages in the optic of management.

Conclusion section: please rephrase the conclusion linking it with the aims of the study and also giving hints for future research in the topic and practical implications and benefit from both the obtained results and the applied approach.

Author Response

Dear Authors,

I have reviewed the paper "Mapping canopy cover in African dry forests from combined use of Sentinel-1 and Sentinel-2 data: application to Tanzania for year 2018". The aims of the paper are germane with Remote sensing applications topic, in this form of article fits with the international scientific standards. The paper is written with a moderate English level. The contribution of this paper to the scientific knowledge is good. Although, in my opinion, there some important flaws and I suggest the corrections in the  following comments.

We thank the reviewer for his/her time reviewing our paper. We addressed the comments raised by the reviewer as detailed in our answers.

Keywords: I suggest to avoid keywords already used in the title, moreover remove the comma after “machine learning”

Thanks for this comment. We think there is a usefulness to repeat some of the words already used in the title. As far as we are aware, this rule is not mentioned in MDPI guidelines for authors: https://www.mdpi.com/journal/remotesensing/instructions#preparation, but we can modify accordingly. We also added some additional keywords not already mentioned in the title.

Reference formatting to be corrected according to the journal’s guidelines

We modified the reference formatting accordingly

Line 49-50: add references for these challenges

We added references accordingly

Lines 97-113: this part of the section is clear and the written concepts are very meaningful and important, however the link between the need of developing more user-friendly procedures for remote sensing of forests and the aim of your study is not clear, in which way this manuscript and the followed approach is answering to the need of making remote sensing monitoring user-friendly?

One of the objective of the study is to demonstrate that open Copernicus data such as Sentinel-1 and Sentinel-2 can be used in combination to existing tools such as Collect Earth and Google Earth and state of the art classification algorithms to map dry forests in East Africa in a replicable way. We are addressing that in the introduction, and we highlighted more in the abstract, objective and discussion parts.

Discussion section: I think authors should highlight in a clear way for the readers what are their innovative findings and most of all the advantages in the optic of management.

We modified the discussion accordingly

Conclusion section: please rephrase the conclusion linking it with the aims of the study and also giving hints for future research in the topic and practical implications and benefit from both the obtained results and the applied approach.

We modified the conclusion accordingly

Round 2

Reviewer 2 Report

Dear Authors, with the changes made the paper is greatly improved. 

It seems  that a good job has been done