Abstract
The world is rapidly urbanizing, but there is no single urbanization process. Rather, urban areas in different regions of the world are undergoing myriad types of transformation processes. The purpose of this paper is to examine how well data from DMSP/OLS nighttime lights (NTL) can identify different types of urbanization processes. Although data from DMSP/OLS NTL are increasingly used for the study of urban areas, to date there is no systematic assessment of how well these data identify different types of urban change. Here, we randomly select 240 sample locations distributed across all world regions to generate urbanization typologies with the DMSP/OLS NTL data and use Google Earth imagery to assess the validity of the NTL results. Our results indicate that where urbanization occurred, NTL have a high accuracy (93%) of characterizing these changes. There is also a relatively high error of commission (42%), where NTL identified urban change when no change occurred. This leads to an overestimation of urbanization by NTL. Our analysis shows that time series NTL data more accurately identifies urbanization in developed countries, but is less accurate in developing countries, suggesting the need to exert caution when using or interpreting NTL in developing countries.
Highlights
Researchers in a range of fields including economics, sociology, and geography have developed urbanization typologies to categorize cities into different classes in order to understand their similarities and differences [1,2,3,4,5]
Only a few studies monitor urbanization dynamics with time series nighttime lights (NTL) data [20,27,28,29]. Differing in their approaches and scopes, these analyses commonly suggest that time series NTL data have enormous potential to characterize urbanization processes at national, regional and global scales
We systematically examined the ability of NTL time series data to characterize urbanization and further analyzed cases of “successes” and “failures”
Summary
Researchers in a range of fields including economics, sociology, and geography have developed urbanization typologies to categorize cities into different classes in order to understand their similarities and differences [1,2,3,4,5]. One of the most common urbanization typologies is based on population size. In addition to a demographic transition, urbanization is a process that simultaneously involves the transition from a rural, agricultural-based economy to an industrial, services-based economy [6,7], and land cover change from more natural ecological systems to the built environment [8,9]. Figures on demographic changes alone are insufficient for providing information about other dimensions of urbanization. Urban areas may change their economic base from agriculture to manufacturing or services. In terms of urban form and structure, urbanization may result in the built environment becoming more linear, dispersed, or compact
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