Multi-Level Dynamic Analysis of Landscape Patterns of Chinese Megacities during the Period of 2016–2021 Based on a Spatiotemporal Land-Cover Classification Model Using High-Resolution Satellite Imagery: A Case Study of Beijing, China

Round 1

Reviewer 1 Report

This manuscript puts forward a land-cover classification method and carries out multi-scale joint analysis and evaluation based on the results of land-cover. The results of this study can be used as a reference for similar study areas. The technical aspects are well described in the correct form. The topic has merit and seems to fit well with the scope of the journal and interest of Remote Sensing readers. There are some minor concerns as follows:

 

(1)   It is mentioned in “Discussion” that the overall accuracy of the land-cover classification method proposed in this study is higher than that of medium-resolution remote sensing images. This result is predictable, after all, this study uses high-resolution satellite imagery for classification. So, compared with the studies using HRRS, how much higher is the overall accuracy of this study or what aspects of this study have been improved?

(2)   The land-cover classification method proposed in this manuscript should be the biggest highlight of this paper, but it is not well reflected in the title. If possible, it is suggested to modify the title.

(3)   In the part of “Abstract”, the first person "we" is used in some places, such as "we established a pixel-object-knowledge…". It is recommended to use the third person.

(4)   Line 73, the abbreviation "HRRS" should be fully written when it appears in the text of the manuscript for the first time.

(5)   Line 457-458, the legend of the bar chart is lack in Figure 8.

(6)   Line 474-475, Figure 9 suggests redrawing, because the green box does not indicate the location.

(7)   Line 505-507, Figure 11 suggests redrawing, because it doesn’t mark “(a)-(d)”.

(8)   Line 234 ,line 237 and line 248, Section 3.3.1 should be Section 3.2.1.

Author Response

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Reviewer 2 Report

My recommendation about the manuscript is MINOR REVISION. 

1) In the introduction, the last paragraph should be deleted. 

2) The authors should improve workflow ( Figure 2). There are some essential missing processing steps—Ex: How the authors get  urban built-up areas from orthorectified fused images. 

3) The authors should provide information about the Gram-Schmidt PS method. Why they selected this fusion method?

 

Author Response

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Reviewer 3 Report

Really interesting paper for those dealing with urban expansion dynamics of metropolitan areas. 

 

I found it rich in metrics for measuring change and also interesting in the way the results of change dynamics are presented. Lots of close-ups and figures of classified areas reported. 

 

I think it can be accepted  after some integrations, mainly at the introduction and the discussion. 

 

For example, into the overview of the space observational program that can be used for land dynamics studies isn’t complete. For example, at minimum, a mention of ESA's Sentinel2 platform should be added. 

 

I think, moreover, the choice of the satellite GF-1 should already be mentioned in the introduction, motivating its importance as an Earth Observation space program for China. There is a wide variety of high-resolution images in the world market. It is necessary to say why GF-1. For easier access to data?   

 

1)Line 138: How many images? Add also a temporal reference concerning the acquisition period. Include, if possible, a reference to the source of the data (i.e. online archive, datasets webpage). 

 

2) In 4.3, for a easier understanding of the results, I would include a reference to Table 4, that defines any calculated indices. 

 

3) Have you ever considered to integrate a vertical dimension of the BUA for a better quantifying  the expansion dynamics (considered here as external or internal expansion) and the density of the internal urban development? Consider to add this aspect in the discussion of the results reporting some relevant bibliography concerning it, if you consider it appropriate.  

 

4) I found discussion poor on references and examples that give added value to this study, in terms of analysis of landscape patterns. This is the core theme of such paper. 

Author Response

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Round 2

Reviewer 1 Report

I think my comments and suggestions have been revised in the revised version, and there are no other comments/suggestions.