Research On Model & Method Of MODIS Water Extraction Based On Sub-pixel Unmixing And Reconstruction

Water remote sensing technology is widely used in dynamic monitoring of flood, drought,water resources,water environment,etc.There are a large number of free remotely sensed data resources with high temporal resolution,high spectral resolution and low spatial resolution,such as MODIS(MODerate-resolution Imaging Spectroradiometer), which is a better data source to large-scale and high frequent water remotely sensed applications.However,the water extraction accuracy can't meet water remotely sensed applications due to the water mixed pixel.Therefore,the study on water sub-pixel unmixing and reconstruction can effectively improve water extraction accuracy and benefit-cost ratio.The research is focused on water mixed pixel based on water spectral feature,imaging mechanism,and pixel's inner structure.It covers remotely sensed image preprocessing, water endmember selection,mixed pixel unmixing,and water sub-pixel location.In the dissertation,the author has established the model of water mixed pixel unmixing and sub-pixel mapping,and designed a series of related algorithms.They can be applied to all multi-spectral or hyperspectral remotely sensed images.The main research and findings are as follows:1) Batch algorithms of geometric correction of MODIS 1B class data is designed and implemented.Batch package is able to correct a pair of 36-band MODIS data in 20 minutes,thus significantly improving data-processing efficiency.2) The author proposes a new initial match algorithm using four-point or six-point groups and area ratio.It accelerates the counterpart points searching by area ratio of adjacent triangles.Experimental results show that it can match two images automatically without manpower intervention and other auxiliary information.3) The author proposes the algorithm of moveably resampled template matching to fine register a pair of different resolution images,which can attain 0.1 pixel precision.It resamples the high-resolution images to a sub-image by a movable template,and then uses template match method to register the sub-image and low-resoiution image. 4) A water extraction decision tree model is established by counting water spectral samples of MODIS.5) A Self-Adaptive Endmember selection algorithm is implemented to solve the problem between more endmember and less band,as well as the linear unmixing program of water mixed pixel is accomplished.6) The author proposes the model and algorithms of water sub-pixel location based on spatial look-up table:①tracking algorithm of water boundary curves;②Endmember coordinate system and its transformation algorithm;③the algorithm to establish Spatial mapping table;④evaluation index system,including curve segments' smooth criteria and minimum clustering distance within pixel;⑤matching algorithm of curve segments between adjacent pixels alone water boundary;⑥dynamic programming searching algorithm of water boundary curves and its solution procedures;⑦conversion algorithms between the serial numbers of boundary curves and endmembers distribution within pixel.