Urban Impervious Surface Automatic Extraction And Spatio-temporal Evolution Process Analysising Arid Areas Based On Light Remote Sensing

With the acceleration of urbanization,impervious surface in the city has expanded rapidly,turning cultivated land,forest land,and water areas around city into impervious land,causing a series of negative impacts on human living environment,air quality,and regional climate.Based on DMSP night light data and NDVI data,this paper took arid areas in our country as research area and established VAISI index applicable to impervious surface extraction in arid areas.Referring to classification results of impervious surface in some cities,we used SVR regression method to construct a regression model between VAISI and reference data,estimated ISP of arid cities,and extracted impervious surface areas in arid regions from 1992 to 2013.Cluster analysis method was used to classify impervious surface changes of arid cities and areas during 22 years.Spacial-temporal changes of impervious surface in arid regions from 1992 to 2013 were quantitatively analyzed according to classification results as well as speed,range,and intensity of urbanization.The main conclusions were as follows:(1)DMSP/OLS night light image and NDVI data performed well in impervious surface extraction process in arid areas when combined with VAISI index constructed by area vegetation coverage,which could meet the requirements of large-scale impervious surface monitoring and serve as a reference for large-scale city impervious surface research in the future.(2)Arid cities could be classified into all-around type,one-way type,and two-way type according to the direction of impervious surface expansion.All-around type included Urumqi and Yinchuan,impervious surface expanded from old city center to the surrounding.One-way type included Karamay and Shihezi,impervious surface expanded in one main direction.Two-way type included Aksu and Bayannur,impervious surface expanded in two main directions.(3)Impervious surface of arid areas kept expanding,but range and speed varied greatly among cities or regions.According to statistical results of impervious surface area in arid areas from 1992 to 2013,they could be classified into high-speed type,rapid type,medium-speed type,and low-speed type.Urumqi,high-speed type,had an area of 67.54 square kilometers in 1992,expanded 13.81 square kilometers per year with an expansion rate of 8.37%.It expanded to 357.46 square kilometers in 2013 and became the largest arid city;Low-speed type included Kezilesu,Wujiaqu and eight other cities and regions,in 1992,the average impervious area was only 1.31 square kilometers with an expansion rate of 8.37%,expanding 0.57 square kilometers per year,in 2013 it expanded to 28.03 square kilometers with an expansion rate of 24.93%,very much different from high-speed type.The impervious area and expansion range of rapid type and medium-speed type were between that of the above two types.