A Study Of Urban Expansion Characteristics Of Ten Big Cities In The Five Central Asian Countries Based On RS And GIS

The five Central Asian countries are important nodes of “The Belt and Road”,which refer to Kazakhstan,Kyrgyzstan,Uzbekistan,Turkmenistan and Tajikistan.In order to smoothly advance the construction of “The Belt and Road” it is necessary to have a more comprehensive study on the economic development of the above-mentioned countries and master the laws of development.Cities carry the national economy,and national economic development will inevitably lead to urban expansion;urban expansion manifests itself as changes in the urban spatial form.Studying the spatial and temporal evolution rule of urban expansion in the five Central Asian countries is an important part of studying the economic development and changes of these countries.Therefore,this paper takes the Landsat remote sensing images of 10 big cities in the five Central Asian countries in 2000,2010 and 2018 as the base of the data and extracts the urban land of 10 big cities.Use urban expansion rate and expansion intensity index to analyze the dynamic changes of urban land,and explore the influence factors of urban expansion.Select urban spatial analysis methods such as compactness index,change of gravity center,equal segmentation method and combine with the three landscape pattern indexes of patch density,landscape shape index and aggregation index to analyze the spatial expansion characteristics.The main conclusion are as follows:(1)The result forms the urban expansion rate indicate that difference in expansion rate of the 10 big cities,Nursultan has the fastest expansion rate among them,and the expansion rate of capital faster than another big city.From the analysis of expansion intensity,Nursultan is the high-intensity growth city among 10 cities;Almaty and Dushanbe are medium-intensity growth cities;Bishkek?Osh?Toshkent?Samarkand?Ashgabat?Turkmenabad and Khujand are steady growth cities.It shows that urban expansion will be affected by natural factors,GDP and population factors.(2)Analysis on the urban spatial expansion characteristics from 2000 to 2018.The compactness of Nursultan,Almaty,Ashgabat and Khujand is continuously increasing,and their urban expansion spatial form developed into compact;but the compactness of Osh is continuously decreasing;the compactness of Bishkek,Toshkent,Samarkand,Turkmenabad and Dushanbe presents“compact-dispersed-compact” pattern.Different cities have different directions ofgravity movement in different study periods.From 2000 to 2018,the urban gravity center of Nursultan moves to the longest distant reached 2294.68 m,and accounting for 50% of the total number of cities moves to east;however,the gravity center of Khujand moves to East with the shortest distant of 521.8m.The urban expansion orientation indicated that the majority cities are dominated by multi-directional expansion.(3)According to the analysis of the landscape metrics,the landscape characteristics of 10 major cities are different.Results show that the PD values of Almaty,Bishkek and Dushanbe had been increasing during the entire study period,it's indicates that the degree of fragmentation of these cities had been increasing year by year with the patch of urban area increasing;the patch density values of Almaty,Bishkek and Khujand are increasing,and the PD values of Samarkand,Ashgabat and Turkmenabad were in a state of fluctuation.The LSI of Nursultan shows that the shape was regular and the urban development is relatively concentrated.Conversely,the shape of Almaty and Turkmenabad was irregular and the degree of aggregation had been decreasing.The shape index continues to increase,with the aggregation index decreases.