Analysis Of Time And Space Change And Drivers Of Urban Expansion In Hunan Province Based On Night Light Data

In order to cope with the implementation of the new urbanization strategy and seize the opportunity of urbanization development,the paper intends to combine the advantages of rapidly developing of remote sensing technology,the spatial-temporal change mode of Hunan Province's towns in recent years is studied by using night light data and statistical data,and its driving factors are analyzed also,so as to provide empirical data for Hunan Province's urban planning.In this paper,the extraction and verification of the built-up areas of the cities in Hunan Province in 1995-2015 is done by using the DMSP/OLS and NPP-VIIRS night light data which are rectified by continuity and saturation effect correction,combined with the statistical data.Urban sprawl spatial overlay analysis,the analysis of the urban center of gravity and the level of urbanization are executed on the extraction results.At the end,the driving force behind urban expansion factors is studied,a BP neural network of the social and economic driving force model of urban expansion is created.The main research contents are as follows:(1)The correction of DMSP/OLS night light data is processed by using the constant target area method,and DN value uniqueness correction of different sensor in the same year and image pixel continuity correction in different years is done at the same time.The continuity and comparability of nighttime light images is confirmed by interpretation and quantitative verification of pixel DN values.At the same time,negative DN values and outlier in NPPVIIRS data is dealt,and continuity processing with DMSP/OLS data.(2)Plaques in the built-up areas of 14 cities in Hunan Province in 1995,2000,2005,2010 and 2015 are extracted by using support vector machine algorithm in which the training samples are selected by comparing with Google Earth images.The built-up areas are verified by using high-resolution landast-8 OLI and statistical data,and human-computer interaction is used in this process.The experiment results showed that the extracted morphological structures of external space and area size precision of Hunan Province is high,and the structural features of spatial morphology of built-up area can be better preserved.(3)In the analysis of spatial and temporal changes in urban expansion,expansion intensity,expansion speed,urban center of gravity distribution,distance of gravity shift and direction,and urbanization level are studied by making maps of urban expansion in Hunan Province and sub-regions since 1995 to 2015.The law of urban expansion in Hunan Province in the past 20 years is analyzed in this paper.The study found that the quantity of the built-up areas of 14 prefecture-level cities in Hunan Province from 1995 to 2015 has different degrees of expansion.The spatial patterns of the expansion of each city are different.The built-up areas of each city are mainly distributed at the intersection of transportation network lines and mainly based on the facet development pattern.In 2010-2015,the speed and expansion intensity of urban expansion in Hunan Province was the largest.The direction of center of gravity of the urban built-up areas in different regions is different.The direction of the center of gravity of the Changsha-Zhuzhou-Xiangtan urban agglomeration has experienced a process from south to north.The southern part of Hunan Province is mainly from the northwest to the southeast.The Xiangxi area is mainly from the northeast.In the trend of migration to the southwest,the area around the Dongting Lake is mainly migrate to southwest.The urbanization level of Hunan Province at various stages mainly shows the trend of high east and low west.Among them,Changsha has the highest level of urbanization and has always ranked first in the level of urbanization in Hunan Province.While the urbanization water in Jishou City in the western Hunan region is the lowest in normal years,it still maintains a trend of growth and change.(4)In the research of the driving factors of urban expansion,the contour method is used to study the urban internal center structure of typical representative cities in various regions of Hunan Province(Changsha,Yueyang,Hengyang,Zhangjiajie).The central structure of the city with single center or multi-center has different influence on the urban expansion.Among them,the diversification of the internal center of the city can promote the urban expansion and development.Based on the overlap analysis between growth area maps of the built-up areas in 1995-2015 and the topographic maps of Hunan Province,it is found that the influence of topographic factors on the expansion of urban built-up areas is greater,and the plains and terraces are more suitable for urban expansion in Hunan Province.The grey correlation model is used to analyze the relationship between social and economic factors and the expansion area of built-up areas in Hunan Province from 1995 to 2015.It is found that the primary socioeconomic driving force affecting the expansion of built-up areas in Hunan Province is the gross domestic product of the second and third industries,and the population density has little influence on the expansion of built-up areas.Finally,the urban expansion model based on social and economic data proves to be able to predict and simulate urban expansion in Hunan Province.