Landsat Satellite Data Based On Cloud Platform Research On Water Extraction Methods

The limited and uneven distribution of water resources and the impact of global climate change and human activities,water shortages and deterioration of water quality are even more common problems.As the source of the san jiang yuan of "China water tower",the importance of surface water research is self-evident.With the continuous development and improvement of remote sensing,there are more and more researches on the accurate and rapid extraction of surface water from satellite remote sensing images.This paper uses the remote sensing big data cloud platform——GEE(Google Earth Engine)and the Landsat TOA(Top of Atmosphere Reflectance,TOA)images stored on it to extract water bodies in the san jiang yuan area from 2001 to 2018.The surface water extraction method is studied in detail,the main contents are as follows:The research of adaptive threshold water extraction method considers that the accuracy is not high when the fixed threshold is used to extract water body in the san jiang yuan.Therefore,on the basis of NDVI and NDWI,an adaptive threshold water body extraction method combining Canny edge detection,morphological expansion operation and Otsu algorithm is used to merge the extraction results of the two kinds of percentile composite images,so as to achieve a high precision annual maximum surface water extraction in the san jiang yuan area,and use the global surface water monthly scale of the joint research center of the European Commission(JRC)with the same resolution.The accuracy of the extraction results is verified by the water body with watered frequency greater than 0 synthesized by monthly history and vectorized image with manual interpretation.It shows that the union of two types of percentile synthetic extraction water bodies can represent the largest surface water body in a year.;The dynamic change of surface water area was analyzed,and the spatial and temporal distribution and area dynamic change of the largest surface water in the san jiang yuan from 2001 to 2018 were presented in the form of mapping and tabulation.Combined with the annual precipitation and annual average temperature interpolated by ANUSPLIN software,the dynamic change of surface water area is analyzed by driving response of climate factors;The results show that the adaptive threshold water extraction method can effectively extract small rivers and other water bodies in the source area of the san jiang yuan with high accuracy.Compared with the JRC monthly history synthetic product,the average annual error of classification is less than 3%,and the average annual leakage error is less than 20%.Eight water bodies in three years are selected for artificial vectorization,and the average annual positive extraction rate is 98.74%;There is a significant positive correlation between the annual maximum surface water area change and the annual average temperature,but the correlation between the annual maximum surface water area change and the annual precipitation is not very significant,so the annual maximum surface water area change is greatly affected by the annual average temperature change.