前言：

一个工程的前期预实验，水体提取比较粗糙，可以改进。

结果展示：

 

 

 

 

一、 研究区范围

var geometry = 
    /* color: #98ff00 */
    /* displayProperties: [
      {
        "type": "rectangle"
      }
    ] */
    ee.Geometry.Polygon(
        [[[133.39612274412107, 45.73460678862749],
          [133.39612274412107, 45.68402125013954],
          [133.51422577146482, 45.68402125013954],
          [133.51422577146482, 45.73460678862749]]], null, false)
Map.centerObject(geometry);

 去云函数

//去云的算法
var cloudMaskL457 = function(image) {
  var qa = image.select('QA_PIXEL');
  // Bit 3 is cloud
  var mask = qa.bitwiseAnd(1 << 3)
            .not();
  return image.updateMask(mask);
};

选择数据集与去云和裁剪：

// M选取Landsat5地表反射率数据
var composite = ee.ImageCollection("LANDSAT/LT05/C02/T1_L2")
    .filterDate('1990-04-01', '1990-10-01')
    .filterBounds(geometry).filter(ee.Filter.lte('CLOUD_COVER',30))
var pixelArea = ee.Image.pixelArea();
var dataset= composite
    .map(cloudMaskL457)
    .map(function(image){
                      return image.clip(geometry)//裁剪
                  })
print("dataset",dataset)

 计算NDWI

var calcNDWI = function(image) {
  var ndwi = image.normalizedDifference(['SR_B2', 'SR_B4']).rename('NDWI'); 
    // var ndwi = image.normalizedDifference(['B4', 'B6']).rename('NDWI'); 
// 在Landsat5中，B2是绿光波段，B4是近红外波段
  return image.addBands(ndwi);
};

// 在数据集中的每个图像上应用NDWI计算
var withNDWI = dataset.map(calcNDWI);

// 设定NDWI阈值，将NDWI大于0的地方判定为水体(可以改)
var yuzhi = function(image){
  image = image.select(['NDWI'])
  var water = image.gt(0);
  
  return water.updateMask(water);
}
var water = withNDWI.map(yuzhi)

计算总区域面积

var totalArea = ee.Image.pixelArea().reduceRegion({
        reducer:ee.Reducer.sum(),
        geometry:geometry,
        scale :30,
        maxPixels:1e13
        }).getNumber('area');
print('totalArea',totalArea)

计算水体面积

var calculateWaterArea = function(image) {
  var waterArea = image.multiply(ee.Image.pixelArea()).rename('WaterArea');
  return waterArea;
};
var waterAreaCollection = water.map(calculateWaterArea);

var extractWater = waterAreaCollection.map(function(image){
  var waterArea = image.reduceRegion({
    reducer: ee.Reducer.sum(),
    geometry: geometry,
    scale: 30,
    maxPixels: 1e13
  }).getNumber('WaterArea');
  var waterAreaProportion = ee.Number(waterArea).divide(totalArea).multiply(100);
  return ee.Feature(null, {
    'WaterArea': waterArea,
    'WaterAreaProportion':waterAreaProportion,
    'Date': ee.String(image.get('system:index')).slice(-8)
  });})

var featureCollection = ee.FeatureCollection(extractWater);

按水体面积降序排序并获取水体面积最大的影像和日期信息

var sortedFeatures = featureCollection.sort('WaterArea', false);
var maxWaterAreaFeature = sortedFeatures.first();
var maxWaterAreaDate = ee.String(maxWaterAreaFeature.get('system:index')).slice(-8);

var data = ee.Date.fromYMD(
  ee.Number.parse(maxWaterAreaDate.slice(0, 4)),
  ee.Number.parse(maxWaterAreaDate.slice(4, 6)),
  ee.Number.parse(maxWaterAreaDate.slice(6, 8))
);
print("data",data)
var nextDay = data.advance(1, 'day');
var maxWaterAreaImage =  withNDWI
    .filterDate(data,nextDay)
    .filterBounds(geometry).first()

输出结果

var waterAreaProportion = ee.Number(maxWaterAreaFeature.get('WaterArea')).divide(totalArea).multiply(100);
print('最大水体面积日期:', maxWaterAreaDate);
print('最大水体面积:', maxWaterAreaFeature.get('WaterArea'));
print('最大水体面积比例:', waterAreaProportion);
// // 在地图上显示结果
Map.centerObject(geometry, 10);
Map.addLayer(maxWaterAreaImage,{min:0, max:30000, bands:['SR_B4', 'SR_B3', 'SR_B2']},'yanmo');

 导出比例结果

// 导出比例EXCEL结果
Export.table.toDrive({
  collection: sortedFeatures,
  description: 'water_area_statistics'+ maxWaterAreaDate.getInfo(),
  fileNamePrefix:'water_area_statistics'+ maxWaterAreaDate.getInfo(),
  folder: 'GEE/kuche/',
  fileFormat: 'CSV'
});

// 导出水体影像
var waterMask = yuzhi(maxWaterAreaImage);
waterMask = waterMask.toInt16();
Export.image.toDrive({
  image: waterMask,
  description: 'max_proportion_water' + maxWaterAreaDate.getInfo(),
  fileNamePrefix: 'max_proportion_water' + maxWaterAreaDate.getInfo(),
  folder: 'GEE/kuche/',
  scale: 30,
  region: geometry,
  crs: "EPSG:4326",
  maxPixels: 1e13
});

Map.addLayer(waterMask, {min: 0, max: 1, palette: ['white', 'blue']}, 'Water');
maxWaterAreaImage = maxWaterAreaImage.toInt16();
// 导出原始影像
Export.image.toDrive({
  image: maxWaterAreaImage,
  description: 'max_proportion_image' + maxWaterAreaDate.getInfo(),
  fileNamePrefix: 'max_proportion_image' + maxWaterAreaDate.getInfo(),
  folder: 'GEE/kuche/',
  scale: 30,
  region: geometry,
  crs: "EPSG:4326",
  maxPixels: 1e13
});

结尾：随便写写，如果能帮到的话，就太好啦