| The expansion of urban construction land is the inevitable result of continuously promoting the urbanization construction.The continuous expansion will lead to the transformation of other land use types,and the competition among various land use types will lead to tension between man and land.We should rationally and effectively control or plan the expansion process of urban construction land or it will cause a lot of social and environmental problems,resulting in unnecessary losses.Since the implementation of the strategies for the development of the western region and the Guanzhong-Tianshui Economic Zone,the urban development pattern with Xi'an as the center and Baoji as the sub-center has gradually emerged.With the implementation of the urban agglomeration development plan in Guanzhong Plain,a new pattern of taking Xi'an as the national central city will be gradually formed.Optimizing the urban scale structure,raising the level of population and economic agglomeration and building a fully functional urban system will become the most important part of the urban construction of various cities in Guanzhong Plain.And Baoji City will usher in a larger and faster urbanization development.The terrain of Baoji municipal district is complex,the space for urban development is insufficient,and the carrying capacity of resources and environment is gradually weakened.Therefore,how to optimize the development pattern and carry out scientific simulation and predictions for the expansion of urban construction land,and how to promote the rational expansion of urban construction land has become the focus of research.Based on the logistic cellular automata(LCA)model,genetic algorithm and variable weight synthesis theory,this paper proposes a variable weights logistic cellular automata(VW-LCA)model,combined with the development law and characteristics of Baoji municipal district.The VW-LCA model is developed on the.NET platform based on the ArcObjects.The data used to simulate or analyze is based on the land use and multi-source,multi-temporal data,including natural and environment data,social and economy data.After the simulation of Baoji municipal district,the feasibility and effectiveness of the improved model are verified.Finally,the situation of urban construction land expansion in Baoji municipal district on 2020 is simulated,and the characteristics of future urban construction land expansion and development trend in Baoji municipal district are analyzed.The main conclusions of this study are as follows:(1)LCA model is a powerful tool to study the expansion of urban construction land,and it can simulate the reasonable boundary of urban construction land expansion according to the effective influence factors.The LCA model is used to simulate the urban construction land expansion from 2010 to 2015.The overall accuracy and Kappa coefficient are 98.77%and 0.982,the value of FoM is 0.042.These indicators indicate that the LCA model is suitable for studying the expansion of urban construction land in Baoji City municipal district.(2)The combination of genetic algorithm and variable weight synthesis theory can be used to implement and improve the LCA model,as well as integrating multi-source,multi-temporal data.Compared with VW-LCA model and LCA model,the results show that VW-LCA model can better reflect the expansion of urban construction land in Baoji municipal district.In the simulation,the two models were set up with the same parameters.The overall accuracy and Kappa coefficient of the VW-LCA model for simulating the expansion of urban construction land in Baoji municipal district from 2010 to 2015 were 98.79%and 0.983,and the value of FoM is 0.150.From a numerical point of view,the overall accuracy of the VW-LCA model is 0.02%higher than that of the LCA model,as well as the Kappa coefficient is 0.001 higher than that of the LCA model,and the FoM accuracy value is 0.108 higher than that of the LCA model.Whether the LCA model or the VW-LCA model,the overall accuracy and Kappa coefficient of the simulation are relatively high,the reason is that the area of urban construction land in Baoji City area is only 3%of the total area,while the forest land,grassland and cultivated land that are dominant,have relatively changed little.Since the FoM accuracy value represents the information of the change region,its value can accurately reflect the accuracy of the model simulation under the scenario.It can be seen that the simulation effect of the VW-LCA model is better than that of the LCA model.(3)The expansion of urban construction land in Baoji municipal district experienced a rapid to slowing process,with growth rates of up to 20.17%between 2010 and 2015.The pattern of "one belt,two wings" development along the banks of the Weihe River is prominent.But from 2015 to 2020,the expansion of urban construction land in all districts will gradually slow down.The mean center of expansion of urban construction land gradually shifts to the east and south.The trend of expansion has driven the entire western region to move closer to the coast of the Weihe River,which has promoted the balanced development of the two districts of Jintai and Weibin,while the eastern and central regions have expanded eastward along the Weihe River.In addition,the trend ellipse gradually shrinks inwards,indicating that urban spatial development in Baoji municipal district has placed more emphasis on optimization and agglomeration.The results of landscape pattern analysis showed that the number of patches of urban construction land in Baoji municipal district increased first and then decreased.In the period of rapid development,new industrial parks gradually formed,and the development characteristics of the area were obvious.In the later period,the emphasis on optimizing the layout reduced the number of patches.The largest patch index and Contagion degree of urban construction land gradually decreased,and the Shannon's Evenness Index gradually increased,indicating that the expansion of urban space in Baoji municipal district not only has obvious effects but also pays more attention to the balance.(4)Using the VW-LCA model to simulate the expansion of urban construction land in Baoji municipal district in 2020,the results show that the future development of Baoji municipal district will pay more attention to structural optimization and layout,and the expansion speed will gradually slow down.Through the statistics and trend analysis of future urban construction land in the area of Baoji municipal district,it can be seen that the development of Baoji's downtown area has gradually changed from "faster" to "better",the urban space has become more and more concentrated,and the urban center gradually moving southward,The development of urban space can be characterized by"eastward expansion and southward shift" and is in line with the urban development strategic objectives.Through the gradual adjustment of the Baoji municipal district,it will develop into a development belt in the central urban area of the municipality and lead the coordinated development of other regions. |
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