Method Of Automated Extraction Of Urban Water Bodies From ZY-3 Multi-Spectral Imagery

As an important component in the urban ecosystem,water bodies play a critical role in maintaining stability of the urban ecosystem.Their changes are closely related with people's life.Negative changes may lead to disasters,pollution,water shortage,surface subsidence,or even epidemics.Therefore,understanding the distribution and changes of urban water has become focus attention.Aiming at the problem of automatic extraction of urban water body,ZY-3 multispectral image is taken as the research object,we refine the Normalized Difference Water Index(NDWI)algorithm to construct two new water indices,namely New Normalized Difference Water Index 1(NNDWI1),which is sensitive to turbid water,and New Normalized Difference Water Index 2(NNDWI2),which is sensitive to the water body whose spectral information is interfered by vegetation,and pre-extraction for urban water.A new normalized difference water index(NNDWI)model is proposed.Aims at the problem that the shadow of high-rise building is difficult to distinguish from the water body,we using a simple traditional spectral relationship to describe the shadow and water object and class small area object generated by NNDWI,we proposed a shadow detection and removal method based on ground object's pixel spectrum statistical feature.Combining NNDWI model and a shadow detection and removal method to obtain the final extraction results of urban water body,experimental results show that proposed algorithm has greater water extraction accuracy compared with NDWI and the Maximum Likelihood Method.In addition,and exhibit greater accuracy when detecting water edge and small rivers.It can effectively distinguish shadows of high buildings from water bodies to improve the overall accuracy.More importantly,the proposed algorithm has more stable detection accuracy than NDWI has when the threshold changes.This method can be used to the extraction of urban water body from ZY-3 images,servicing in urban water resources investigation.