Urban Expansion Analysis Based On Cellular Automata And Data Assimilation

In the current wave of rapid global economic development,urbanization development emerged as an inevitable phenomenon of social and economic development.In order to seek a better harmonious development path between man and nature,build a rational and effective urban living environment,and study urban expansion.The situation is particularly important.At the same time,the study of urban expansion has become one of the major research topics in urban development planning in China and the world.At present,China's urban development is in the stage of rapid expansion and development.The city is facing an irreconcilable problem in the rational planning of urban land development,the supply and demand of production and life,and the effective use of environmental protection and resources.Urban expansion studies have played a key role in rational urban planning and in coordinating the relationship between humans and the environment.The current urban expansion is mainly based on urban geography.It predicts urban expansion from a qualitative perspective.There are few quantitative models combined with predictive models to expand urban phased changes.This paper uses remote sensing data and GIS to study urban development.And use the forecasting model to carry out urban expansion forecasting research,quantitatively analyze urban expansion characteristics and driving factors analysis,and achieve the purpose of guiding urban sustainable development and rational planning urban land use.This paper takes 11 central districts and counties under the jurisdiction of Chengdu,one of the six central cities in China,as the research area.Based on the Landset+ETM remote sensing data of 1985,2000 and 2015,the urban land use space in downtown Chengdu Distribution information extraction.Based on the remote sensing interpretation data and the existing research area data,combined with the multi-level constraint conditions of geographic elements,the relevant logical parameters are used to establish the cellular automata(CA)model transformation rules,and the geographic information spatial analysis technology is used.Urban land expansion model coupled with CA model and data assimilation algorithm(EnKF).And the simulation result correction model is established to improve the accuracy of data assimilation-CA simulation prediction.Then use Matlab software to carry out the simulation results by using CA iteration to implement the model running code,and realize the urban expansion result on ArcGIS software.The traditional logistic autonomic machine model and the cellular automaton model based on data assimilation are used to simulate and compare the models.The model with better simulation accuracy is used to predict the urban development changes in the study area in 2030.Finally,the simulation results are analyzed for urban variation characteristics and influencing factors.The main conclusions are as follows:(1)The results of urban expansion forecast show that from 1985 to 2000,the downtown area of Chengdu has been concentrically expanding to the periphery,and the rapid development of satellite cities has occurred in individual areas far from the city center.The results predicted by the Logistic-CA model indicate that the development of downtown Chengdu and the trend of actual urban changes are consistent.From 2000 to 2015,the degree of urban change in Chengdu was more obvious,and the area of the central city more than doubled,extending radially around the satellite city.From the prediction of the EnKF-CA model from 1985 to 2000,the newly added land is mainly concentrated in the existing urban fringe areas,which are mainly distributed in the west and southwest of the central city,while the small patches are scattered.The spatial distribution is not obvious.From 2000 to 2015,the expansion of urban construction land is more obvious,and the area of change is relatively large.The large-scale plots mainly develop along the urban radial roads along the satellite urban areas that extend farther to the edge,mainly concentrated in the middle and double streams of Wenjiang District.The changes in construction land in the southern and southwestern parts of the district,the central part of Longquanyi District,the central part of Xindu District and the central part of the Yudu District are consistent with the actual urban development.(2)Prediction accuracy by comparing results show EnKF-CA model in both areas of the city complete block prediction effect,right at the far edge of the city of distance of the city the variances of the simulation of the land for construction of small towns and Kappa coefficients is superior to Logistic-CA model,the Kappa coefficient was 0.128 and 0.059,the reason of the respectively is that EnKF-CA model by iterative calculation and model correction for many times to reduced the accumulative error and improve the simulation accuracy.(3)Spatial variation characteristics of land use in the central urban area of Chengdu:From 1985 to 2015,the urban land area of the research area was on the rise especially the fastest of 2000 to 2015,and was close to the total area of the previous two periods.The expansion intensity of urban land in the past 30 years is 0.910km~2/year,and the expansion type is medium-speed expansion,and the dynamic attitude of expansion is 8.13%,and the dynamic attitude of expansion is medium-speed expansion.Among them,the urban expansion from 2000 to 2015 is obvious,which is a type of rapid expansion.Among them,the urban expansion from 2000 to 2015 is obvious,which is a type of rapid expansion.According to the analysis of the change of land use type transfer in the research area,the urban construction land in the central area of chengdu is mainly converted from the cultivated land type,and the cultivated land type transfer accounts for 94.40%of the total transfer amount,while other types are relatively few.The main center of gravity of the city shifted to the southeast direction,the center of gravity transfer distance is large.Through the analysis of buffer zone of urban land,it can be seen that the increase scope of construction land in the research area is mainly concentrated in the range of 20-40km from the city center,while other areas are expanded,but the expansion area is not large.(4)According to the analysis of the factors influencing the change of urban land use,the main reasons for the current urban change in Chengdu are the development of regional economy and population in terms of social and economic factors,which lead to the continuous expansion of urban area.To some extent,government decisions also play a role in urban planning and development.Natural factors of urban road traffic and terrain also play a role in the establishment of the city to a certain extent,the urban form and outward expansion of the directional factors are mainly restricted by the traffic and transportation.Especially the urban expansion from 2000 to 2015,it indicates that the transportation conditions in this period have become the main natural factors for urban development.