Restoration Of Landsat-7 SLC-OFF Image And Its Application On Analysis Of Dynamic Variation Of Vegetation

On April 15,1999,National Aeronautics and Space Administration(NASA)launched the Landsat 7 satellite(Landsat-7)which carries the Enhanced Thematic Mapper Plus(ETM+)sensor.Compared with Landsat-5,Landsat-7 not only adds the panchromatic band(PAN)whose spatial resolution is 15 m,but also increases a lot of new features,so it has been widely applied.Landsat-7 scan-line corrector(SLC),a mechanism designed to correct the undersampling of the primary scan mirror,failed on May 31,2003.With the SLC now permanently turned off,the ETM+ is losing approximately 22%of the data due to the increased scan gap.It greatly limits the use of data.However,the data itself still retains some good radiometric and geometric properties;it can be used in some special purposes if they are properly repaired.First,this paper makes a comparison with the different restoration methods of Landsat-7 SLC-OFF image and selects the best method to restore these images.Secondly,it uses these restored images to inverse the vegetation coverage change of Cha-Kou Small Watershed in 2000-2010.Finally,it analyzes the response of vegetation coverage to the climate change and the topography change with meteorological data and topography data during the same period.Main research results are as follows:(1)Adaptive local regression match not only solves the interference of distant pixels to pending-restore pixel in global restoration methods,but also avoids the influence of sample being too much or too less.So,Adaptive local regression match can gain the best effect.(2)The average vegetation coverage of study area was 0.51 during 2001-2010.The vegetation coverage in the west of study area is higher.Moreover,the vegetation coverage of wood land,plain land and dam land are relatively higher than the rest.(3)During 2001-2010 the vegetation coverage of study area,whose average rate of change is 0.013/year,exhibit an increasing trend,especially in eastern and southern regions.(4)There is a positive correlation between vegetation growth and temperature or rainfall,and rainfall is the main climate factor limiting vegetation growth.The influence of rainfall but not temperature on the vegetation growth shows an obvious time lag.(5)As the highest altitude in study area is not up to the critical value limiting vegetation growth,vegetation coverage increases with the increase of altitude.And vegetation coverage increases with the increase of slope until the slope is up to the critical value when vegetation coverage decreases with the increase of slope.