| Urban agglomeration is an important carrier of the transfer of world economic gravity,it's the core area of China's economic development strategies and the main body of new urbanization,also the key gateway for China to participate in economic globalization.Nighttime light data,as a new data source for the urban agglomeration studies,has strong application and analysis ability.At present,the two generation of main night light data such as DMSP/OLS and NPP/VIIRS have different resolution,spectral response and other parameter information,the mismatch of parameter information leads to the fault of time series in nighttime light data.Firstly,based on the DMSP/OLS nighttime light data,this paper combined the image processing methods such as fitting and filtering,and using the NPP/VIIRS data to simulated the DMSP/OLS data,so as to integrated nighttime light data and built up areas of the Main Urban Agglomeration of the Yangtze River Economic Zone(MUAYREZ)was further extracted.Then,from the three aspects of the scale,form and structure of those cities,we selected ten indexes or models such as the total value,standard deviation ellipse,fractal dimension,rank-size rule and so on to analyse the built up areas extraction results,and summarized the development characteristics of MUAYREZ.Finally,based on MODIS NDVI data and WESTDC2.0 land cover data,we estimated the average vegetation cover changes and the losses of ecosystem services value,and analyzed the impact of urban agglomeration development process on the internal and external ecological environment.The main conclusions are as follows:(1)It is feasible to integrate the two classes of night light data resources for the need of urban agglomeration research.The similarity between the DMSP/OLS data simulated from NPP/VIIRS data and the real DMSP/OLS data is high,the correlation coefficients of Pearson in 2012 and 2013 is 0.87 and 0.86 respectively,and the standard errors were reduced to 7.24 and 6.27,respectively.The total area error of the built-up areas extracted from the integrated nighttime light data set is only 7.81%.All this show that the method of data integration is feasible and has achieved good results.(2)The integrated nighttime light data successfully applied to characteristic analysis of the Urban Agglomeration development process.During the study period,MUAYREZ developed rapidly,the total value of nighttime light scale increased by 3.6 times,the shape of the built up areas tended to be complex and concentrated.Large cities,such as Shanghai,Wuhan and Chongqing,were important power sources for the growth and development of this urban agglomerations.Because of the differences in the base of development,the natural environment,and other factors,the Yangtze River Delta Urban Agglomeration(YRDUA),the Yangtze River Middle Urban Agglomeration(YRMUA)and the Chengdu-Chongqing Urban Agglomeration(CCUA)have different development characteristics.(3)The integrated nighttime light data successfully applied to the ecological environment impact analysis of the Urban Agglomeration development process.During the development process of 2001~2016 years,the average vegetation coverage in the built-up area was gradually increased from 37.86% to 45.28%,the expansion of the built-up areas to the outside cause a loss of about 2 billion 748 million Yuan in the ecological services value,in MUAYREZ.In conclusion,this study took the MUAYREZ as a case,and obtained high quality data integration results,development characteristics analysis results,and ecological environment impact analysis results.Data integration extends the time series of the urban agglomeration researches that based on nighttime light data,it is useful for exploring the potential application of nighttime light data in other research fields.It has important reference value for the development,the planning,the formulation and implementation of the policy of each urban agglomerations that analysis and comparison results of nighttime light data in MUAYREZ. |
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