GEE 代码片段

ImageCollection转多波段Image

// 1. 用toBands()内置函数
var ndvi = finalImage.toBands();

// 2. 遍历ImageCollection,并组合
var ndvi = CollectionToImage(finalImage);
function CollectionToImage(collection){
  var stack = ee.Image(collection.iterate(function(img, prev) {
    return ee.Image(prev).addBands(img);
  }, ee.Image(1)));

  stack = stack.select(ee.List.sequence(1, stack.bandNames().size().subtract(1)));
  return stack;
}

给feature编号

trainPoints = trainPoints.map(function(feature) {
    return ee.Feature(feature.geometry(), {'id': feature.id()})
})
print(trainPoints)

---

FeatureCollection的批量下载

https://zhuanlan.zhihu.com/p/80340644

var l8 = ee.ImageCollection("LANDSAT/LC08/C01/T1_SR"); 
var roi = /* color: #d63000 */ee.Geometry.Polygon( 
        [[[115.64960937499995, 39.112756306811285], 
          [116.28681640624995, 39.163883889810315], 
          [116.21540527343745, 39.58850167846649], 
          [115.70454101562495, 39.6054326422912]]]); 
function rmL8Cloud(image) { 
  var cloudShadowBitMask = (1 << 3); 
  var cloudsBitMask = (1 << 5); 
  var qa = image.select('pixel_qa'); 
  var mask = qa.bitwiseAnd(cloudShadowBitMask).eq(0) 
                 .and(qa.bitwiseAnd(cloudsBitMask).eq(0)); 
  return image.updateMask(mask); 
} 
var l8Imgs = l8.filterBounds(roi) 
               .filterDate("2018-1-1", "2018-3-1") 
               .map(rmL8Cloud); 
print("l8Imgs", l8Imgs); 
Map.addLayer(l8Imgs, {min:0, max:3000, bands:["B4","B3","B2"]}, "l8Imgs"); 
Map.addLayer(roi, {color: "red"}, "roi"); 

//影像集合导出方法 
function exportImageCollection(imgCol) { 
  var indexList = imgCol.reduceColumns(ee.Reducer.toList(), ["system:index"]) 
                        .get("list"); 
  indexList.evaluate(function(indexs) { 
    for (var i=0; i<indexs.length; i++) { 
      var image = imgCol.filter(ee.Filter.eq("system:index", indexs[i])).first(); 
      image = image.toInt16(); 
      Export.image.toDrive({ 
        image: image.clip(roi), 
        description: indexs[i], 
        fileNamePrefix: indexs[i], 
        region: roi, 
        scale: 30, 
        crs: "EPSG:4326", 
        maxPixels: 1e13 
      }); 
    } 
  }); 
} 
exportImageCollection(l8Imgs); 

---

FeatureCollection属性求和、导出特定属性

var yearbook = [35645.99,178861.26,3417100.00,1742220.00,3823900.00,2699308.33,4287242.00,5480666.67,1236.60,509760.00,
  63282.46,1234756.43,33053.93,47600.00,3871090.00,3818010.00,751991.20,384380.00,123140.00,596973.00,440929.20,1839360.00,
  501460.00,1802457.28,1179440.00,1000810.46,21370.00,322730.00,1051050.00,]
var predict = ee.FeatureCollection(feature_list)

predict = predict.flatten().aggregate_array("sum");
predict.evaluate(function(predict_local) {
  var result = linearRegression(predict_local,yearbook)
  print(result)
  var chart = ui.Chart.array.values(predict_local, 0, yearbook)
  print(chart)
  }
)
var Feature_Collections = ee.FeatureCollection(feature_list).flatten()
print(Feature_Collections)
// print(Feature_Collections)
Export.table.toDrive({
  collection: Feature_Collections,
  folder: '_ZonalStat',
  description: output_name,
  selectors:["PROVCODE","PROVCODE_D","PROVNAME","sum"],
  fileFormat: 'CSV'
});

下载哨兵RGB数据

var district_geometry = geometry
function maskS2clouds(image) {
  var qa = image.select('QA60');
  // Bits 10 and 11 are clouds and cirrus, respectively.
  var cloudBitMask = 1 << 10;
  var cirrusBitMask = 1 << 11;
  // Both flags should be set to zero, indicating clear conditions.
  var mask = qa.bitwiseAnd(cloudBitMask).eq(0)
      .and(qa.bitwiseAnd(cirrusBitMask).eq(0));
  return image.updateMask(mask).divide(10000);
}
var rgbVis = {
  min: 0.0,
  max: 0.3,
  bands: ['B4', 'B3', 'B2'],
};
var exportdataset = ee.ImageCollection('COPERNICUS/S2_SR')
                  .filterBounds(district_geometry)
                  .filterDate('2021-09-01', '2021-11-30')
                  // Pre-filter to get less cloudy granules.
                  .filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE', 10))
                  .map(maskS2clouds)
                  .select(['B4', 'B3', 'B2']).median();
Map.addLayer(exportdataset, rgbVis, 'RGB');
Export.image.toDrive({
    image:exportdataset,
    description:'wuhan',
    scale:10,
    maxPixels: 1e13,
    region:district_geometry,
    fileFormat: 'GeoTIFF',
    crs:"EPSG:4326",
    fileDimensions:2048,
    formatOptions: {
      cloudOptimized: true
    }
  });