| Impervious surface is a substance that water can not permeate directly,it mainly consists of cement,metal,asphalt and other materials,such as buildings,roads,etc.It is of great significance in measuring the urbanization process,monitoring the ecological environment,changing the land use pattern and other national basic geographical conditions.With the rapid development of social productive forces,the process of urbanization has been accelerating.A large number of agricultural land has been converted into construction land,and the water impervious area has expanded rapidly.This paper chooses Chengdu as the research area,because that it is one of the representative cities of urbanization in this paperst china.In this paper,Landsat TM/OLI remote sensing images are selected as the key data sources.The main purpose of this paper is to extract impervious surface and surface temperature,and study the temporal and spatial variation of impervious surface,and its relationship with urban ecological environment.The main research results are as follows:(1)Preprocessing the multispectral data,including geometric correction,radiometric calibration,atmospheric correction,regional cutting,etc.The endmember of four types of ground objects is obtained by means of MNF and PPI,including high reflectivity,low reflectivity,vegetation and four elements of soil.LSMM uses four endmembers to decompose pixels of the image.Impervious surface images are obtained by linear spectral unmixing,but it contains some information about water and vegetation.Therefore,this paper remove these “noise information” by building water masks and vegetation masks.Finally,this paper obtains the impervious surface abundance images of the study area.In order to test the accuracy of data,this paper calculates the RMS value,and the mean variance is less than 0.01.At the same time,the result image is checked with the high resolution images,and the correct rate is higher than 80%.Therefore,impervious surface abundance images are real and effective.(2)This paper uses the radiative transfer equation to deal with the thermal infrared band and obtains the surface temperature results.At the same time,this paper compares the inversion values of surface temperature with the meteorological station measurements.The results show that the inversion value of surface temperature is close to the real temperature,and it is available.(3)Through statistical analysis and spatial analysis,the temporal and spatial variation of impervious surface in the study area is obtained.The impervious surface of the study area continued to grow from 2006 to 2015,and reached 70.51% in 2015.The impervious surface coverage of the study area decreases successively from Wuhou District,Qingyang District,Jinniu District,Jinjiang District,Gaoxing District,Chenghua District.The distribution of impervious surface in the study area is characterized by the ring from center to outside.Moreover,the expansion speed of impervious surface is the fastest in the central city,followed by the southwest and northwest of the study area,and the southern part of the study area.(4)In this paper,the relationship between impervious surface and surface temperature is studied by means of buffer analysis and regression model.Through the buffer analysis,the study area is divided into different ranges.And the impervious surface abundance values and temperature values of discrete points are analyzed at different urban scales.The correlation coefficients are greater than 0.7,which indicates that impervious surface is positively correlated with temperature.(5)On the basis of comprehensive analysis of impervious surface and surface temperature,this paper puts forward the optimization plan of urban planning and construction.It includes improving the greening area,adjusting the urban construction plan,designing the buildings reasonably,reforming the urban spatial development pattern and protecting the original ecological environment. |
