Review Reports

Round 1

Reviewer 1 Report

This is an interesting and structurally good looking paper. I have only few recommendations. First, the language could still be polished in order to improve readability and second a consideration of relatively close indices values in Shannon and Batty numbers. They seem very close to each other and perhaps also consideration regarding alternative ways of analyzing urban sprawl could be considered. As the results show, the used methods are in some cases not the best possible ones. Finally, a critical and more extensive consideration of the limitations and benefits of the used indices could be helpful.

Author Response

Thank you for your constructive comments. We revised the manuscript to convey its meaning more clearly. We think there is no best a single index representing urban sprawl. We tried to point out the strengths and weaknesses of the indices and sugget a better index. We rewrite the results to provide the reader with a more critical interpretation of the results. We hope the revised manuscript’s readability has improved.

Reviewer 2 Report

 

 

Comments for author File: Comments.pdf

Author Response

Thank you for your constructive comments.

We revised the manuscript to convey its meaning more clearly. The following revisions were made according to our interpretation of your comments:

1. Rationalization

We think that entropy is a useful index to measure the urban sprawl as both concepts are related to the entity’s order/disorder. In addition to the conceptual compatibility, it has good strength as an index, such as requiring minimum information (e.g., land cover maps) and being easily calculated using basic software. We hope our study provides not only information about entropy indices but also the pitfall or precautions of the indices (results).

2. Method

We think the administrative boundary is important in urban sprawl because it is the basic unit of planning and developing an urban area. Although the effects of urbanization extend far beyond the boundary, the city’s actual development occurs within them. As we showed, the adjacent cities have been developed differently. Changwon expanded after merging with neighboring cities, Masan and Jinhae, in 2010. The old Changwon area has maintained its characteristics as a planned city in contrast with Masan and Jinhae that developed naturally

3. Execution

We revised the method section extensively to convey the meaning clearly.

 

Introduction

We revised the introduction for better readability.

The reviewer asked why the reason Shannon’s index is prevailing despite Batty’s old critique. It is an interesting question, and we want to know it as well. Although the concept of spatial entropy was suggested more than 40 years ago, it had gained less attention until recently, partly due to computation loads and lack of qualified spatial data. More importantly, we think this delay is related to “academic inertia”. Researchers are kin to use widely referenced models, which provide safe shelter for defense.

 

Methods

Entropy is calculated based on the built-up area, not considering other types of land coverage. In this case, the p_i means that the amount of built-up area (cell number) in an i^th zone over the total built-up area. We modified the manuscript to convey these considerations more clearly.

As the reviewer kindly indicated, inappropriately defined zones can mislead the interpretation of results. It is a well-known problem of sensitivity to zone boundaries. It is also mentioned in many documents and our manuscript. It is a crucial issue in dealing with entropy, and we agree that a detailed urban sprawl study must be considered. We intend to show more general characteristics of entropy but mentioned it briefly as well.

The city center may not be the most important topic, but it is still worth mentioning. The concentric ring zoning is prevailing in urban sprawl research, and the center of the ring can seriously affect the result. Nevertheless, how to define the city center is controversial, and there is no consensus. We chose the center of mass as an objective way to define the city center in urban sprawl research.

The decadal land cover map was created based on the multi-year images and the provider does not specify the year of the map. Therefore, we cannot indicate the specific year for the map.

 

Results

We revised the results and discussions to convey the key messages more clearly. We hope the manuscript is more readable.

Once more, thank you for your constructive comments.

Round 2

Reviewer 2 Report

The article is improved. The main issues are with the clarity of the language and the overall contribution of the research.

On the first, there are a few quick changes that could improve readability further:

• Avoiding passive voice.
• Breaking large paragraphs into more manageable chunks with clear points (p.6)
• Carefully reviewing syntax (potentially by a copy-editor)

On the second point, the authors can better convey the interpretation of the entropy index. Readers will want to ascribe meaning to the index values (Table 3). Entropy indexes are notoriously difficult to interpret on their own; they gain significance in comparison. This is exactly what the authors do and I think it merits a clear explanation to avoid misunderstanding. Basically, explain that the indexes on their own have limited interpretation, but that they are useful for comparing cities, hence the need to be confident that we are using the right index.

I agree with the authors that the entropy index is one of the simplest measures of sprawl and researchers will, therefore, continue to use it. As such, this study is a useful reference doing to the ground work of establishing one index over another. To the extent that the authors can insure that their paper comes up when researchers look for methods to measure sprawl, the article could be a useful one indeed.

Author Response

Thank you for your constructive comments.

We have rechecked the manuscript again to convey its meaning more clearly. The revisions were made according to our interpretation of your comments.

We hope the manuscript is more readable.

Once more, thank you for your constructive comments.