Analysis And Research On Urban Dynamic Expansion Based On Landsat And DNISP Images

Since the reform and opening up,the level of urbanization in China has been accelerating,and urban construction has brought a certain impact on natural resources,the environment,and ecological balance.How to balance the relationship between urban expansion and social development has become the focus of research by experts and scholars.In this paper,using remote sensing and GIS technology,based on the Landsat data and DMSP/OLS night light data of 1992,1996,2000,2004,2008 and 2012 as research data,the maximum likelihood classification and optimized dynamic threshold dichotomy were used to extract the built-up areas,then,overlay the data to further obtain the precise built-up area.On this basis,the expansion area,expansion speed,and expansion dynamic index are selected from the amount of space-time in the built-up area,select the expansion trend,fractal dimension,and compactness index from the perspective of spatial pattern,to analysis of the dynamic changes in the pattern of urban built-up areas in Qingdao.At the same time,from the two aspects of natural environment and human driving,the driving force behind the urban expansion of Qingdao is studied.Among them,the slope,the altitude,the topography,the distance from the sea are selected in the natural environment,and the human driving factor is the number of population,the total economic volume,the investment in fixed assets,and the number of tourists.The main conclusions of this paper are as follows:(1)From the analysis of spatial and temporal changes,the built-up area of Qingdao has been on an upward trend from 1992 to 2012.Among them,the area of urban built-up area was 120.41km~2in 1992 and the area of urban built-up area in 2012 rose to571.11km~2,close to five times the area of the urban built-up area in 1992.The area of the built-up area of the urban area is ahead of other counties in various periods,and the expansion area of each county varies in size in different periods.From the perspective of expansion speed(V),the built-up area of Qingdao from 1992 to 2012 can be regarded as undergoing the"fast-slow-fast-fast-slow-high-speed"expansion process.The expansion curve of the built-up area in the urban area fluctuates uniformly.To some extent,the expansion speed of the built-up area in the urban area determines the expansion speed of Qingdao.Based on the natural break method in Arc GIS,the threshold is selected,combined with the previous research and the actual situation of Qingdao City,Qingdao expansion is divided into 5 expansion types according to the expansion dynamics(K),high-speed expansion type(K>50%),rapid expansion type(20%<K<50%),moderate expansion type(10%<K<20%),low expansion type(0<K<10%),negative expansion type(K<0).In the same period,the types of expansion in different cities are not the same,and the expansion rate is different;in different periods,the types of expansion in the same city are also different.From an overall point of view,the expansion of built-up areas in Qingdao experienced a development process from fast to slow and then from fast to slow.The expansion of built-up areas developed in a volatile manner.(2)From the analysis of spatial pattern changes,the expansion trend of built-up areas in Qingdao from 1992 to 2012 showed a"spreading pie"pattern,but the expansion trend was not uniform in terms of stages and counties.The fractal dimension(S)of urban construction is basically maintained at about 1.2,fluctuating in different periods but the fluctuation range is not large.The urban built-up area realizes the sprawl growth by combining the external expansion and internal filling,but the city outline is still relatively simple.The compactness(C)of urban built-up areas is generally low.Among them,from1992 to 1996,the compactness of cities did not change significantly.The increase in urban compactness in 2000-2004 and 2008-2012 indicates that the urban built-up area during this period was dominated by internal filling.From 1996-2000 and 2004-2008,urban compactness decreased,indicating that this stage is dominated by external expansion.(3)In the analysis of the driving factors for the urban expansion of Qingdao City for a total of 20 years from 1992 to 2012,in the natural environment,slope,elevation,and topography have an impact on the urban built-up area.In particular,urban built-up areas tend to expand in coastal areas with smaller slopes,lower elevations,and flat terrain.That shows that slope,elevation,topography and the distance from the sea are important factors that affect the expansion of urban built-up areas.In terms of human driving factors,through the correlation analysis of population,economic aggregate,fixed asset investment,number of tourists and urban built-up area,it can be found that the relationship can be expressed in linear terms,and the correlation is high.The judgment coefficient R~2is basically greater than 0.8,only a few counties are less than 0.8.Therefore,it was determined that the number of population,total economic volume,investment in fixed assets,and the number of tourists played an important role in the expansion of Qingdao from 1992 to 2012.