Study On The Evolution Of Urban Land Forms And Their Spatial Influence Factors In Nanjing Based On Multi-scale And Multi-models

The city is a dense combination of people and buildings with a certain area covering the surface of the Earth.Since the beginning of the 21st century,the rapid development of China’s economy has accelerated the pace of urbanization,making the issue of urban expansion and urban land distribution become the city’s geography.Studies and the hot issues of urban land use research.The influencing factors of the study on the distribution of urban land are the key issues that many scholars are paying close attention to.Urban expansion is a continuous and dynamic process of change in time.It has changes in quantity,that is,the growth of urban construction land area.It is spatially expressed as a process of continuous change in the structure and shape of the city.It is called the evolution of urban spatial form,which leads to the change of urban form and its distribution.Study the spatio-temporal changes of urban expansion,explore the temporal and spatial evolution characteristics and influencing factors of urban land use,and have certain reference significance for urban planning,land use planning,and the government’s introduction of relevant regulatory policies.This study is based on the Landsat TM remote sensing images of Nanjing City in 2004,2007,2010,2013 and 2016.The characteristics of spatio-temporal evolution of urban sprawl in Nanjing in recent years were analyzed.Multi-model research methods were used to study the impact of urban land use distribution in Nanjing on multiple scales.Potential spatial influence factors:Select the urban infrastructure and business service locations(POI points of interest data)that may affect the distribution of urban land in Nanjing and divide it into 23 spatial influencing factors at 100*100m,200*200m5 300*300m.At the scale of 400*400m and 500m*500m5 the spatial least-squares regression model,the spatial regression model(SLM and SEM)s and the geographically weighted model(GWR)were used to compare and analyze the spatial impact of urban land and its spatial influencing factors,and to explore the city of Nanjing.The potential spatial influence of land use distribution.The results show:(1)Nanjing’s internal structure tends to be stable,its external profile tends to be compact,and its main urban area expands and weakens;the expansion model mainly focuses on the development of the Yongjiang River,and Nanjing’s built-up areas gradually form a "two-belt-one-axis" urban spatial structure pattern.And it is a multi-center development trend;Nanjing’s urban expansion pattern is in a non-equilibrium space differentiation state,and the direction of urban expansion is mainly concentrated in the north,southwest,and southeast of Nanjing City,and has obvious stage characteristics.(2)The results of the spatial regression model for spatial distribution of urban land use are better than those of ordinary least-squares regression models;the road density in the 23 spatially-influencing factors affecting urban land use in Nanjing proved to be an impact on the distribution of urban land use.The largest,GDP density and distance from the company’s factory,and distance from life service facilities are important factors affecting the distribution of urban land in Nanjing;the influence coefficient of some space influencing factors shows an irregular trend with different scales and models.The scale effect is obvious,indicating that these spatial influence factors are very sensitive to the scale and model in the study of the driving mechanism of urban land distribution.(3)The results of geographically weighted regression model(GWR)estimation show obvious spatial heterogeneity,that is,the spatial influence factors have different effects on different geographical locations in Nanjing,and the direction and intensity of impact have certain differences.The analysis results of these spatial influencing factors are closely related to the distribution of urban land in the study area and the development context of the city;when choosing the research scale,we should weigh and select the appropriate spatial scale and spatial geography information that can be reflected by the research model.The level of detail,on a more elaborate scale,is more detailed in the description of the impact of urban land use distribution.When the scale is gradually increased,the large-scale smoothes the detailed differences in the adjacent areas;the GWR model can obtain other influencing factors at a certain position.The value of the contribution of urban land use distribution is horizontally compared with it.More importantly,it can obtain the influence degree of spatial influence factors in different locations and can obtain the weight of the influence of spatial influence factors on different geographical locations.This information has important reference value for guiding the rational distribution and planning of urban land.