Analysis And Forecast Of The Expansion Characteristics Of Built-up Areas In Guangxi Province Based On Multi-source Data

China's urbanization process leads to the expansion of construction land,which has seriously squeezed agricultural and other land.However,how to attain the maximum benefit balance between construction and lien,and how to quantitatively monitor the trend of urban construction land and its expansion is an urgent scientific problem for policy makers.Based on the multi-source remote sensing image data,this paper extracted the area of construction land from 2003 to 2019,analyzed the spatial and temporal characteristics of the expansion of the built-up area,and used the gray prediction model to forecast the expansion of the built-up area,and obtained the following understandings:(1)The natural discontinuity method is adopted to determine the image threshold,and the time series of remote sensing noctilucent data with consistency is established to determine the optimal threshold by mutual correction.The maximum threshold of DMSP/OLS data is 63,but after saturation correction and invariant region method correction,its maximum threshold can reach 171 to a certain extent,so it can be mutually corrected with NPP/VIIRS to extract the optimal threshold.Combined with Landsat data and Guangxi Zhuang Autonomous Region Statistical Yearbook data,the method is borne out.The results demonstrate that the accuracy is high and the extraction results are reliable.(2)the spatial characteristics of the amount,shape,and direction of the expansion of built-up areas were analyzed from the perspectives of landscape pattern index,expansion speed,expansion intensity,compactness and fractal dimension.Being dependent on the analysis,the urbanization in Guangxi Zhuang Autonomous Region was in a period of rapid growth from 2003 to 2011,and urbanization was mainly extensional expansion.The urbanization progress slowed down obviously from 2015 to 2019,and urbanization was mainly filled expansion.On the whole,the expansion structure of the built-up areas in Guangxi Zhuang Autonomous Region belongs to the simple type,and the expansion is mainly extensional expansion,and the expansion rate decreases year by year from 2003 to2019,and the urbanization progress is relatively slow.(3)The results show that economic progress is the main driving force for the expansion of built-up areas in Guangxi Zhuang Autonomous Region through the analysis of a single factor and multi-factor.The municipal population and GDP have a significant promoting effect on the expansion of built-up areas.Policy factors and ecological factors also have a definite impact on the expansion of built-up areas.(4)The grey prediction model GM(1,1)for Guangxi Zhuang Autonomous Region from 2003 to 2019 was constructed,and its accuracy was verified by residual error,posterior error,and correlation degree test methods,which indicated that the prediction results of this model had a high accuracy,and the expansion of built-up areas in Guangxi Zhuang Autonomous Region from 2020 to 2025 was predicted.Through comparison and analysis with Guangxi Economic Development Yearbook,the prediction model of urban construction land monitored by remote sensing noctilucent image conforms to the historical data,so there is sufficient scientific basis for the expansion prediction in the next five years,and the results can provide for accurate policy implementation.