| Since the 16 th National Congress of the Communist Party of China will be "the urbanization with Chinese characteristics" is raised,the urban construction upsurge in the country,in 2020,our country's urbanization rate is about 64%,the urban population accounted for about 45%,in the process of the development of the urbanization,big cities have very strong leading role of radiation,driving the development of small and medium-sized cities around concentrated,formed the urban agglomeration,Urban agglomeration becomes a new engine of regional development by virtue of perfect industrial cluster and large economic volume.In 2016,Ha-Chang urban agglomeration,one of the national city clusters,was formally born as an important starting point for the revitalization of northeast China,and planned the long-term goals for it.However,urbanization not only promotes social progress and improves national material living standard,but also inevitably has negative impact on ecological environment.Therefore,only by accurately understanding the dynamics and patterns of urban expansion in the process of urbanization,and timely preventing and solving the ecological and environmental problems in the process of urban expansion,can sustainable development be achieved.At present,the development of satellite remote sensing technology is outstanding,and its characteristics of high efficiency,intuitive and objective have unique advantages for the study of long-term series of large regional urbanization.The spectral characteristics of remote sensing images can also be used for the inversion study of ecological factors.Based on this,this study uses Google Earth Engine cloud computing platform to process NPP/VIIRS,Landsat 8,MODIS and other large data remote sensing images.By constructing VBANUI index and combining statistical data,the urban built-up area of Ha-Chang urban agglomeration from 2013 to 2020 is extracted.Changes from urban expansion,city scale and transfer trajectory of the center of gravity of the three angles explores the ha long urban agglomeration spatial pattern evolution,and through the inversion of the green degree of heat,moisture,dryness,and four ecological elements to construct ecological index,remote sensing quantitative grading evaluation,long the change of urban agglomeration in the process of development of ecological quality.The achievements of the above research work are as follows:(1)Extraction of urban built-up area.Through GEE cloud computing platform,using NPP/VIIRS and Landsat 8 remote sensing images,based on the understanding that the urban built-up area is inversely correlated with NDVI and positively related with NDBI,VBANUI method is established to extracted the urban built-up area of HaChang urban agglomeration from 2013 to 2020.After statistical data testing,High precision of urban built-up area extraction is obtained.(2)Study on the evolution of spatial pattern.From the perspective of urban expansion,the urban built-up area of Harbin-Yangtze urban agglomeration increased continuously from 2013 to 2020,but the change degree was small,mainly occurring around the main urban area.From the perspective of city scale change,the total amount of light in Ha-Chang urban agglomeration increased significantly during the eight years from 2013 to 2020.According to the total amount of light at night,11 cities in Ha-Chang urban agglomeration were divided into three echelons,and the change degree was ranked according to the growth rate and increment.From the perspective of the change of development gravity center,the development gravity center has always been located at the junction of Harbin and Changchun from 2013 to 2020,and the development gravity center of Ha-Chang urban agglomeration has moved toward the southeast as a whole in the past 8 years.(3)Ecological quality evaluation.Based on GEE cloud computing platform,using MODIS remote sensing data retireval 4 kinds of ecological factors.Through principal component analysis,remote sensing ecological index was constructed to quantitatively evaluate and spatially display the ecological quality of Ha-Chang urban agglomeration from 2013 to 2020,and the changes of ecological grade were statistically analyzed.The results show that the ecological quality of the eastern part of the Ha-Chang urban agglomeration is better than that of the western part.53.25% of the regional ecological environment deteriorates,while 46.75% of the regional ecological environment remains unchanged or improves.The improvement of ecological environment mainly occurred in the eastern part of urban agglomeration and on both sides of the river,mainly in Mudanjiang City,Yanbian City and Daqing City.The deterioration of ecological environment mainly occurred in the central and western regions,with Changchun City,Siping City,Liaoyuan City and Harbin City experiencing significant environmental degradation.The research results of this paper can provide some references for the government departments to make development plans scientifically,adjust development direction in time and make rational spatial layout. |
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