Analysis Of Spatial And Temporal Changes Of Urban Development In Countries Along “The Belt And Road” Based On Multiple Remote Sensing Data

“ The Belt and Road ” strategic concept is the first great strategic vision proposed by General Secretary Xi Jin ping in 2013,which has been fully supported and responded to by various countries around the world since its submission.“The Belt and Road ” is a strategic concept of economic development,throughout the world's several countries,is the world's longest economic corridor of the word.There fore,with the continuous development of the economy,the expansion of towns and cities is accelerating.The development of towns and cities also makes the area of urban land expand and has a certain impact on ecological balance,natural environment and natural resources.The understanding of the spatial pattern and process of the town can not only provide some scientific basis for the future development planning strategy of the town,but also play a certain role in promoting the healthy development of the town.As the two core contents of remote sensing,the rapid development of sensor and satellite technology makes remote sensing have the ability to obtain the most accurate information of urban extension in the shortest time.The study of urban development has always been a major research hot topic in academic circles,and the application of remote sensing technology has made the study of urban development highly concerned by the scientific community in the study of urban expansion.In the past,the research mainly used Multiple Remote sensing Data to quantitatively analyze a certain subregion or individual country in “The Belt and Road”,but there was less research on the spatiotemporal dynamics of urban night lighting scale in the whole area of“The Belt and Road”,and the comprehensive use of multi-source remote sensing data to supplement and verify each other can further improve the accuracy of the study.In this paper,65 countries along“The Belt and Road ”are the scope of the study,selected in line with the countries and regions along the route to 2000 years,2004,2008,2013 DMSP/OLS nighttime lights data,combined with population density data and other social statistics such as MODISNDVI data,and studies the characteristics of spatial and temporal variation of cities and towns along the“The Belt and Road”in recent 13 years.The urban extension characteristics of the study area are studied and analyzed from the regional and individual urban scales by using various indexes such as the proportion of urban land use,the expansion speed,the expansion attitude,the expansion strength,the shift of center of gravity,fractal dimension and compactness,respectively.The main conclusions of the paper are as follows:(1)This paper will overlay Multiple Remote sensing Data and higher resolution Landsat8 remote sensing data,and setting up a number of threshold methods to achieve the accurate extraction of urban land space information,and extracting the urban area range,the overall accuracy can reach more than 90%.This method has great applied potential in the study of large scale urban expansion.(2)During the period 2000-2013,the countries along the “ The Belt and Road”showed an upward trend from the proportion of urban land,and the European region has obvious advantages.In terms of expansion speed,China is the fastest expanding country in the city,The Russian and Mongolian regions and West Asia are developing faster and stable,Europe are developing faster but the rate of expansion is fluctuating,and the expansion rate of Central Asia and Southeast Asia and South Asia is slow,which is closely related to the economic structure and development between regions.When the overall development base of the economy reaches a certain level,the pace of urban expansion will gradually slow down.(3)According to the urban expansion Attitude Index,this study divides the expansion of cities along the route into five types: high-speed expansion(K>20%),rapid expansion(15% <K?20%),Medium-speed expansion(10% <K?15%),lowspeed expansion(5% <K?10%)and slow expansion(K?5%).In the 2000-2013,China's urban expansion rate was the fastest in the countries along“The Belt and Road”,and countries along the route showed a circumstances as expansion of speed up after 2008.(4)In the analysis of spatial dynamic evolution,the urban center of gravity of the study area shifted 107109 m to the northwest direction during 2000 to 2004.During 2004 to 2008 years the center of gravity moves to the southeast direction of443814.1628 m.From 2008 to 2013,the center of gravity moved 452927 m to the southeast.Overall appears to be consistent with the direction of gravity shift in each region.The countries along“The Belt and Road”have remained in a more complex situation of space evolution from 2000 to 2013,with the most unstable areas being the Russian-Mongolian region.(5)According to the changes of three stages in 2000-2004,2004-2008 and2008-2013,the compactness of the whole study area showed an increase and decrease of two trends.The expansion trend of most cities along “ The Belt and Road ” is exterior extension.Overall,the urban exterior forms in Maldives,East Timor,Nepal and Bhutan are more compact and are filled.The calculation shows that China,West Asia,Central Asia,Europe,Southeast Asia,South Asia,Russia andMongolia urban compactness index on average 0.024,0.17,0.268,0.198,0.274,0.385,0.28 and,in the past 13 years have not changed much more,which indicating that the urban form in the spatial expansion of the difference tends to stabilize.