// 去云

var maskL8 = function(image) {

var qa = image.select('BQA');

var mask = qa.bitwiseAnd(1 << 4)

.or(qa.bitwiseAnd(1 << 8));

return image.updateMask(mask.not());

};

// 增加水体指数

var addVariables = function(image){

var awei= image.expression(

'4*(green-SWIR1)-(0.25*NIR+2.75*SWIR2)',{

green:image.select('B3'),

NIR:image.select('B5'),

SWIR1:image.select('B6'),

SWIR2:image.select('B7'),

}).float().rename('AWEI')

var ndwi = image.normalizedDifference(['B3','B5']).rename('NDWI')

var mndvi = image.normalizedDifference(['B3','B6']).rename('MNDWI')

var lswi = image.normalizedDifference(['B5','B6']).rename('LSWI')

return image.addBands([awei,ndwi,mndvi,lswi]);

}

// 研究区域

var roi = ee.FeatureCollection("users/comingboy1118/China/CH_shi");

var roi = roi.filter(ee.Filter.eq("市","杭州市"))

Map.addLayer(roi,{"color":'red',},"roi")

Map.centerObject(roi, 8)

var landimg= ee.ImageCollection('LANDSAT/LC08/C01/T1_RT_TOA')

.filterBounds(roi)

.filterDate('2019-01-31','2019-12-31')

.map(maskL8)

.map(addVariables)

.mosaic()

.clip(roi)

// 真彩色

Map.addLayer(landimg, {bands: ['B5', 'B4','B3'],min: 0, max: 1,gamma:3,opacity:1},'landimg');

//显示水体指数

var visParams = {min: -0.8, max: 0.8, palette: [ 'green','white','blue']};

Map.addLayer(landimg.select('AWEI'),visParams,'AWEI');

Map.addLayer(landimg.select('NDWI'),visParams,'NDWI');

Map.addLayer(landimg.select('MNDWI'),visParams,'MNDWI');

Map.addLayer(landimg.select('LSWI'),visParams,'LSWI');

// 通过阈值提取水体

var ALOSDEM = ee.Image("JAXA/ALOS/AW3D30_V1_1");

var slope = ee.Terrain.slope(ALOSDEM.clip(roi));

var AWEI = landimg.select('AWEI');

var water=AWEI.gt(-0.005).updateMask(slope.lt(10)); //snow and shadow mask by DEM data

var water=water.updateMask(water.gt(0.5));

Map.addLayer(water,{min: 0, max: 1,palette: ['white','blue']},'water');

//其它监督学习方法提取然后进行检验--

// 哎呀，接下来我也不会了，要不有读者给我讲讲