Spatial-temporal Evolution Of Urban Expansion In The Yangtze River Delta Urban Agglomeration Based On NPP-VIIRS Data

This paper selects the nighttime lighting data of NPP-VIIRS in June 2012,June2014 and June 2016,and uses the binary iteration method based on statistical data to extract and verify the precision of the built-up area of the Yangtze River Delta urban agglomeration,and use the urban land to grow.The types,urban expansion direction,and compactness of urban built-up areas analyze the laws and characteristics of urban land expansion in the Yangtze River Delta urban agglomeration.The results show that:(1)Annual changes in the area of built-up areas of the cities and towns of the Greater Triangle City Group from 2012 to 2016.The total area of ??the Yangtze River Delta urban agglomeration built-up area increased from 6912.24km2 in2012 to 6112.84km2 in 2016,an increase of 693.6km2.From 2012 to 2014,it increased by 445.14km2,and from 2014 to 2016,it increased by 248.46km2.From2012 to 2016,the area of the built-up area of the Yangtze River Delta urban agglomerations increased in quantity.The highest growth is Shaoxing.It is102.74km2,and the lowest growth rate is-1.27km2 in Chizhou City.The extent of expansion: from 2012 to 2016,the largest expansion of the built-up area of the Yangtze River Delta urban agglomeration is the largest in the B category,which is24.38%;followed by the small city,18.54%,and the medium-sized city,which is14.88%.The smallest expansion is A.Large cities,5.54%.Expansion rate: Among the four types of cities in the Greater Triangle City Group from 2012 to 2016,the expansion rate of the Big B city is the highest,at 79.67km2/a,followed by the big city of Class A,with a growth rate of 32.75km2/a;The growth rate is 18.37km2/a;the lowest growth rate is in small cities with a growth rate of 7.94km2/a.From 2012 to2016,the higher the city level in the Yangtze River Delta urban agglomeration,the higher the night light plaque area index;the lower the city level,the lower the night light plaque area index;from 2012 to 2016,the Yangtze River Delta city The higherthe level of the cities in the group,the higher the average light intensity;the lower the city level,the lower the average light intensity;the elastic coefficient of land use growth: the urban growth coefficient of the big cities in the four major cities of the Yangtze River Delta is the closest.1.12,the growth of the urban built-up area is the most reasonable.(2)Urban Distribution Center: The urban distribution center of the Yangtze River Delta urban agglomeration is located in Wuxi City,Jiangsu Province.After the latitude and longitude coordinates search and verification,the distribution center of the 2012 Yangtze Delta urban agglomeration is located near Huanghua Port,Yixing City,Wuxi City,Jiangsu Province.The distribution center of the triangular city group is located near Dagang,Yixing City,Wuxi City,Jiangsu Province.From 2012 to 2016,the distribution center of the Yangtze Delta urban agglomeration moved to the northwest by 2.82 km.The spatial pattern of urban land use: the mature triangle city from 2012 to 2016 The lowest compactness of the group outside the city is Shanghai,which is 0.12,and the highest is Chizhou,which is 0.68.Among the four major cities in the Yangtze River Delta urban agglomeration,the higher the city type rank,the lower the compactness of the city,and the compactness of various cities from 2012 to2016 is continuously decreasing;the urban expansion orientation: the Yangtze River Delta urban agglomeration The city is dominated by multi-directional expansion;the type of urban land expansion: the type of urban land expansion in the Yangtze River Delta urban agglomeration is dominated by extension-filling enhancement.The application value of this paper is to use NPP-VIIRS night lighting data to extract the built-up areas of the Yangtze River Delta city and analyze the characteristics of urban expansion.