Impervious Surface Extraction Based On Multi-scale Remote Sensing Images

With the fast development of urbanization,the vegetation and water-dominated natural landscape is gradually replaced by impervious surface area.This has a significant negative impact on urban environment.Timely understanding of spatiotemporal information of impervious surface has become more and more urgent as it is important for monitoring dynamics of impervious surface and evaluating the corresponding impact on urban environment.Taking Fuzhou Basin as a case,this thesis investigated the extraction techniques of impervious surface and the effects of impervious surface on thermal environment based on multi-scale remote sensing images.Firstly,the linear spectral mixture analysis(LSMA)model and the normalized difference impervious surface index(NDISI)were used to extract impervious surface from images with a medium resolution.Secondly,for high resolution images,stratified classification and object-oriented classification were tested,respectively.Accordingly,this thesis revealed the dynamics of the impervious surface coverage in the study area during a 25-year period from 1989 to 2014.Furthermore,the thermal environmental effects of the impervious surface was discussed both in residential units scale and in Fuzhou Basin scale.Finally,the evolution of the thermal environment in Fuzhou Basin and its causes were analyzed and some suggestions were put forward to improve the thermal environment.For images with medium resolution,a sharpened land surface temperature and the Soil Adjusted Vegetation Index(SAVI)were applied to modified the Normalized Impervious Surface Index(NDISI).The modified NDISI are found to have been in an improved resolution.Compared with the LSMA,the modified NDISI is a better choose for the fast extraction of impervious surface in a large region.During the impervious surface extraction of high resolution images,a blue roof index(BRI),the Normalized Difference Mountain Vegetation Index(NDMVI),the Normalized Difference Water Index(NDWI)and the H component of IHS transform,were constructed respectively,in order to enhance the blue roofs,vegetation,water bodies,and bare soils.A multi-band image was formed based on the four index and the original image bands.In the new multi-band image,vegetation(both in shadow and non-shadow areas),water,bare soils,and blue roofs were well enhanced,which benefited the extraction of various impervious surfaces.The impervious surface areas of 1989,1996,2006 and 2014,were extracted with the modified NDISI,and its dynamic changes were analyzed subsequently.The result showed that in the 25 years from 1989 to 2014,Fuzhou Basin experienced a rapid expansion centered on the old urban down town.The impervious surface increased by 2.3 times,from 6150.68 hm2 to 20413.70 hm,with an average annual growth area of 570.52 hm.In the period of 1989 to 2006,both the expanding in size and expansion velocity reached the maximum of the 25 study years.The combined effects of economic,demographic,transportation,government decision-making and natural geographical factors are supposed to be the main driving force for the impervious surface expansion of Fuzhou Basin.The impervious surface growth from 2006 to 2014 is much slower than that of the previous phases,due to the decrease of available space for the expansion of the impervious surface.Moreover,the thermal environment effect of impervious surface was studied.It was found that impervious surface percentage(ISP)and land surface temperature(LST)were in a significant exponential relationship.A high ISP could accelerate the LST rise.On the contrary,vegetation and water show a cooling effect on thermal environment.In the fine residential units scale,a multiple regression analysis was processed to test the influence of impervious surface,water and vegetation on local thermal environment.The result suggested that impervious surface was still a major factor in the thermal environment of residential areas.Change analysis of Fuzhou Basin thermal environment showed that,from 1989 to 2014,Fuzhou Basin was on the trend of warming up and the overall thermal environment of the Basin deteriorated,but in the urban area some local improvement still existed.To improve the thermal environment of Fuzhou Basin,some measures should be taken,for example,improving the greening rate of urban areas,the reconstruction of old urban areas.