Research And Application Of RS Estimation Of Urban Impervious Surface Extracting Based On Linear Spectral Mixture Model

The impervious surface is one of the most important components of the city, itschange can objectively reflect the urban expansion and urbanization. So there are moreand more researches on the impervious surface at home and abroad, and is wildly used inurban ecological environment monitoring, urban hydrology study, the heat island effectand thematic mapping. In this paper, we use Landsat ETM~+remote sensing image as datesources, Hefei for the study area, combined with spectral mixture analysis relatedmethods. The spectral unmixing method was respectively used on the original reflectanceimage and the normalized reflectance image of Hefei, both in summer and winter image.Select the most accurate image to extract urban impervious surface on the basis ofcomparative analysis of classification accuracy, and GIS analysis was to study the spatialpattern of the impervious surface and dynamic changes in Hefei, and so on.（1）Spectral unmixing method accompanied by restrictions was respectively usedon the original reflectance image and normalized reflectance image, both in summer andwinter image, and their classification accurancy were compared, the results show that: Insummer for the study area, The RMS(Root Mean Square) error of ETM~+image beforeand after normalized dispectively were0.002368,0.008900. The results all can meet theaccurancy of linear spectral mixture, especially in summer original reflectance image. Tofurther evaluate the precision, we use aerial imagery date in2007to choose the right kindof points, to do accurancy validation and error analysis, the R~2value is0.8363, indicatingthat the two were significantly correlated. In addition, we computed the RMS error andsystematic errors, respectively was5.23%and7.71%.（2）In this experiment, there is no obvious advantage for the normalizedreflectance image compared with the original one. And there is no significantly improvedfor the impervious surface classification accurancy in the study area. Because thenormalized method can effectively remove or reduce the brightness variation, eliminatesome redundant information, but also caused a lot of information loss. （3）Extracting the impervious surface information of Hefei based on the result ofLinear Spectral mixture method with the original reflectance ETM~+image in summer,and analysis the spatial pattern of the impervious surface in Hefei, from the impervioussurface distribution map, we drawn that: within the first ring road, the averageISP(impervious surface percentage) is73.49%; Between the first and second Ring Road,the average ISP is61.39%; Between the second and third Ring Road, the average ISP is48.63%; And outside the central old city to outward, the ISP is gradually decreasing. Theaverage ISP in LuYang District is28.49%, in YaoHai District is31.94%; in ShuShanDistrict is28.33%; in BaoHe District is24.60%. The ISP in each regions are generallybetween20%-30%, and a littler lower, which the YaoHai district has the highest ISP, only31.94%, which maybe because it has larger area and larger percent of vegetation andwater.（4）To study the expansion of urban impervious surface of Hefei from2002to2008obtain the spatial distribution characteristics and the evoluement trends of urbanimpervious surface in the six years, reveal the influences of urban development onimpervious surfaces. The ISP2008increased significantly compared with2002,especially between the first and second Ring Road, and between the second and thirdRing Road, the ISP increased by17.99%and21.70%respectively, The ISP of YaoHaiDistrict and ShuShan District increased by21.17%and15.28%compared with2002,which have an obvious increasing. Due to the contrition of the new district, the HeFeiEconomic and Technological Development Zone, Long gang comprehensive EconomicDevelopment zone, YaoHai industrial park, the built-up area of HeFei has been greatlyimproved, especially for the percentage of the high reflectance object outskirt the city.Relatively Speaking, the new city contraction area of LuYang District and BaoHe Districtare not large and have no significant increase in the ISP. Also found that the old city moatwithin the scope of the highest percentage ISP up to80%, and had a slight increase in sixyears, deserved our further attention that should increase the ecological contraction of thecentral urban greening.