function maskL8sr(image) { // The third bit is cloud and the fourth bit is cloudshadow。 var cloudShadowBitMask = 1 << 4; var cloudsBitMask = 1 << 3; // Get QA_PIXEL band. var qa = image.select('QA_PIXEL'); // Set the cloud mask to zero var mask = qa.bitwiseAnd(cloudShadowBitMask).eq(0) .and(qa.bitwiseAnd(cloudsBitMask).eq(0)); // Update the cloudmask return image.updateMask(mask) .select("SR_B.*") .copyProperties(image, ["system:time_start"]); } // Map the function over 3 months of data and take the median. // Load Landsat-8 surface reflectance data. var landsat8 = ee.ImageCollection("LANDSAT/LC08/C02/T1_L2") .filterBounds(table) .filterDate('2019-1-01','2020-1-1') // Pre-filter to get less cloudy granules. .filter(ee.Filter.lte('CLOUD_COVER',5)) .map(maskL8sr) .median() .clip(table); landsat8 = landsat8.uint16(); print(landsat8);// visualize the datasets var rgbVis = { min: 8400, max: 15000, gamma:1.5, bands: ['SR_B4', 'SR_B3', 'SR_B2'], }; Map.addLayer(landsat8,rgbVis,'landsat8'); var imgselect = landsat8.select('SR_B2','SR_B3','SR_B4','SR_B5'); //Export image to google drive and then download Export.image.toDrive({ image:imgselect, description:'2019yaogan', scale:30, region:table, folder:"result", crs: "EPSG:4326", maxPixels: 1e13 });将这一段利用Landsat的代码改写成使用哨兵2

Sure here's the modified code to use Sentinel-2 instead of Landsat:

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 the masked image, scaled to reflectance, without the QA bands.
  return image.updateMask(mask)
    .select('B.*')
    .multiply(0.0001)
    .copyProperties(image, ['system:time_start']);
}

// Load Sentinel-2 surface reflectance data.
var sentinel2 = ee.ImageCollection('COPERNICUS/S2_SR')
  .filterBounds(table)
  .filterDate('2019-01-01', '2020-01-01')
  .map(maskS2clouds)
  .median()
  .clip(table);

sentinel2 = sentinel2.uint16();
print(sentinel2);

// Visualize the datasets
var rgbVis = {
  min: 0.0,
  max: 3000.0,
  gamma: 1.5,
  bands: ['B4', 'B3', 'B2'],
};
Map.addLayer(sentinel2, rgbVis, 'Sentinel-2');

var imgselect = sentinel2.select('B2', 'B3', 'B4', 'B8');

// Export image to Google Drive
Export.image.toDrive({
  image: imgselect,
  description: '2019yaogan',
  scale: 10,
  region: table,
  folder: 'result',
  crs: 'EPSG:4326',
  maxPixels: 1e13
});

Note that Sentinel-2's surface reflectance data has a different band naming convention and scale factor compared to Landsat, so the code has been modified accordingly.