Study On Urban Expansion In China Based On Nighttime Light Data

Since the reform and opening up in 1978,the rapid economic development and the increasing population have led to the rapid expansion of China's cities and the remarkable spatial expansion of cities nationwide.The study of urban expansion in China in recent years is of great significance to the rational and scientific planning and construction of cities and the promotion of coordinated development of various regions.This article selects China as the research area,and selects the data between the national "Ninth Five-Year Plan" and the "Twelfth Five-Year Plan",namely the DMSP/OLS lighting data in 1995,2000,2005,and 2010 and and the NPP /VIIRS lighting data in 2015 as the basic data,extract the built-up areas of Chinese cities in these five periods,and use Landsat TM images as auxiliary data for accuracy verification,from urban expansion speed,expansion intensity,standard deviation ellipse,center of gravity change and urban external shape The spatial pattern changes of various regions in China from 1995 to 2015 are analyzed in terms of compactness and other aspects.The main conclusions of this study are as follows:(1)This study uses the statistical data comparison method to extract the extent of built-up areas in each region of China.After the comparison and verification with statistical data and the accuracy verification of Landsat data,it is proved that the extraction of built-up areas using nighttime light data is feasible and can be used in the study of urban spatial expansion in China.(2)Analysis of the changes of the extracted built-up areas in China in each year shows that the area of urban built-up areas in China increased exponentially from 1995 to 2015,and the expansion rate of East China and South China was relatively fast from2000 to 2015,while the urban expansion rate of Northeast China was relatively slow,and the expansion rate of the rest of the regions was less different in each year.The expansion intensity in Central China,Northwest China and Southwest China increased year by year,and the rest of the regions alternated between increasing and decreasing expansion intensity.(3)In terms of the standard deviation ellipse,the direction of the standard deviation ellipse is northeast-southwest in all regions except for northwest,east and central China.The standard deviation ellipse in Northeast,Central,East and Southwest China does not change much,and is relatively stable within the region;the largest increase in ellipse area in Northwest China indicates that the expansion intensity is large after the implementation of the Western Development Strategy,and the urban development is relatively scattered;in North and South China,the two phenomena of internal urban filling and external expansion coexist.(4)In terms of the change of the center of gravity,the light center of gravity in each region is shifted by national policies,regional development differences,economic and demographic factors.In general,the change of center of gravity in northeast China is mainly influenced by the revitalization of the old industrial base in northeast China;east and south China is due to the influence of the coastal economy brought about by the superior geographical location;north China's center of gravity moves due to the driving effect of Beijing,Tianjin and other major cities;central China is influenced by the strategy of the rise of central China;northwest and southwest China are influenced by policies such as the western development and the Belt and Road.(5)In terms of compactness,except for some regions where compactness increased from 1995 to 2000,the compactness of all regions decreased in all years,indicating that urban construction tended to be discrete and gradually expanded from the center to the outside under the increasing built-up area of each region.2010-2015 saw a larger decrease in compactness,indicating that the inner cities of each region were relatively saturated in that time period,and cities favored external expansion and at a faster rate.(6)In terms of urban expansion drivers,the value of primary industry is the primary factor influencing urban expansion in Northeast,Central,Northwest and Southwest China,the primary factor influencing social fixed asset investment in North China,the primary factor influencing GDP in East China,and the primary factor influencing gross construction output in South China.