Research On The Status Quo And Forecast Analysis Of Main Urban District Expansion In Nanchang City Supported By RS And GIS

At present,our country is experiencing rapid urbanization.Research on urban expansion with GIS and RS as technical support that can provide decision-making basis for urban planning and management.This paper takes the main urban area of Nanchang City as the research object and adopts six periods of Landsat TM/ETM+/OLI remote sensing image as data source.Then it uses satellite remote sensing technology and GIS spatial analysis methods to study the change of urban construction land from 1991 to 2016.By extracting land-use type information,we can grasp the spatial-temporal characteristics of its expansion.Combining regional physical geography and socio-economic development data to analyze the extended impact factors.Last the CA(Cellular Automata)model based on artificial neural network was used to predict the land use change trend in the main urban area of Nanchang City in 2021.The main research contents and achievements of this article are as follows:1)In the face of the extraction of urban land use information over a span of 25years,image data from six periods(1991,1996,2001,2007,2011,and 2016)were selected.The CBI(Combinational Build-up Index)was used to extract building features and combined with the SEaTH(separability and thresholds)algorithm for image classification.Compare the classification results with the classification results of the three supervised classifications(maximum likelihood,neural network,support vector machines).It was found that the image classification effect based on the CBI index and the SeaTH algorithm was better.With high extraction accuracy,the status of city expansion in six periods was finally obtained.2)Using GIS technology to extract the built-up land area of the main urban area of Nanchang City,and analyze the time characteristics of urban expansion according to the expansion speed and intensity index.It was found that the main urban area of Nanchang City experienced a low speed-medium speed-high speed-high speed-rapid expansion process.Combined with quadrant analysis and buffer analysis methods to study its spatial characteristics,the spatial characteristics of the main urban area of Nanchang City are characterized by internal filling and epitaxial expansion.3)From a qualitative and quantitative perspective,a detailed analysis of the driving forces of expansion was conducted.Eleven indicators were selected,and two common factors were extracted using principal component analysis.Regression analysis was used to construct a regression model of urban built-up area change,and the impact factors were determined.Qualitatively elaborated the influencing factors of social economy,population,transportation,natural conditions and government-related policies.4)Using the artificial neural network CA model,improve the expression of the traffic factor in the CA model.Considering the neighborhood environment,terrain conditions,accessibility of traffic road networks,and obtaining conversion rules through neural networks,the land use in the main urban areas of Nanchang City in2007 and 2016 was simulated.According to the point-by-point comparison method,the Kappa coefficient for two years is 0.82 and 0.85.Based on this simulation of land use in the main urban area of Nanchang City in 2021,the built-up area of the main urban area of Nanchang City in 2021 was 661.58 km~2,an increase of 66.17 km~2from2016.Among them,the expansion of newly constructed areas is the most prominent,while the expansion of Qingyun District and Wanli District is relatively slow,indicating that the development space in urban areas has reached a certain degree,and the urban expansion mainly shifts to XinJian District,followed by Wanli District.