Monitoring Three-Decade Expansion of China’s Major Cities Based on Satellite Remote Sensing Images

Round 1

Reviewer 1 Report

This manuscript presents three decades of urban expansion in China’s major cities using remotely sensed satellite images. The manuscript presents good work, complemented by detailed explanations, tables, and figures. I have some minor concerns and suggestions.

-The authors must clarify the research question/s and the novelty of their study in the introduction section.

-Line 58 “The previous studies have discussed a lot on the dynamics and the related factors of China’s urbanization”. The authors focused their literature review only on China. I would suggest discussing some recent work on urbanization causative factors in other countries such as:

>Maimaitijiang, M., Ghulam, A., Sandoval, J.S.O., Maimaitiyiming, M., 2015. Drivers of land cover and land use changes in St. Louis metropolitan area over the past 40 years characterized by remote sensing and census population data. Int. J. Appl. Earth Obs. Geoinformation 35, Part B, 161–174. https://doi.org/10.1016/j.jag.2014.08.020

>Mustafa, A., Rompaey, A.V., Cools, M., Saadi, I., Teller, J., 2018. Addressing the determinants of built-up expansion and densification processes at the regional scale. Urban Stud. 55, 3279–3298. https://doi.org/10.1177/0042098017749176

>Traore, A., Watanabe, T., 2017. Modeling Determinants of Urban Growth in Conakry, Guinea: A Spatial Logistic Approach. Urban Sci. 1, 12. https://doi.org/10.3390/urbansci1020012

-Line 153: “In particular, we focused more on the “boundary” around urban and rural.” How did you set this boundary?

-Line 167: “For each target pixel, searching in its eight-neighborhood, the target pixel and its neighborhood pixels whose ISA fraction was greater than 0.5 (i.e. high-density) were assigned as the…” How did you decide the thresholds for urban densities (for example 0.5 for high-dens)? Why did you consider the neighborhood as eight cells and not cells that have a shared boundary with the target cell? Did you perform any sensitivity analyses?

-In the results section, the authors must list and discuss the image classification accuracy assessment. I found some information on this regard in the Discussion section but I would like to see this as a part of the results.

-Line 315: “The Ordinary Least Square (OLS) regressions between ISA and GDPPC, and between ISA and TP show that the determination coefficients (R2) for most cities are greater than 0.9 (Table S2).” What about the regression's residuals?

-English needs moderate changes.

-I hope this helps.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Very excellent assessment of urban growth patterns. I enjoyed the use of the sprawl trajectory curve types and investigate of patterns in old city zones.

line 85 - spell out GDP and GCT, then provide abbreviations for future use in text.

Figure 5: please add a bit more detail to caption to help the reader determine what the different shades mean in each bar.

Figure 8: looks like the letters are missing from the graphic boxes.

I'd like to see the content in the discussion split up and moved into 1) the methods - how did you assess accuracy, and 2) results - how accurate was the ISA assessment. Then you can include a bit more information in the discussion about the limitations and strengths of the research and how it compares to other studies. Some of these elements currently are included in the conclusion. I recommend moving those pieces into the discussion and making the conclusion a more concise summary of your work.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The study aim is to present the Research on “The three-decade expansion of China’s major cities as recorded in satellite images” The manuscript is presented clearly and nicely. However, to have scientific merit, the following comments should be addressed. I would like to suggest a Major revision for this paper. Pls, see attach Pdf for more details. 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Dear Authors, I would like to thank you for having accepted and implemented our comments and suggestions. I’ve found the manuscript deeply improved, good job!

Author Response

Thanks for your helpful advices again!