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I am trying to use the functions proposed at Creating Sentinel-2 cloud free, cloud-shadow free composite or scene on Google Earth Engine (GEE)? to mask out clouds in a collection and display the results.

However, when I display the images, clouds are not masked.

What am I doing wrong?

Here is my code:

var aoi = <br />
    /* color: #d6cfcd */<br />
    /* shown: false */<br />
    /* displayProperties: [<br />
      {<br />
        "type": "rectangle"<br />
      }<br />
    ] */<br />
    ee.Geometry.Polygon(
        [[[19.11805207896173, 68.89159582156138],
          [19.11805207896173, 68.53463738722539],
          [20.46937043833673, 68.53463738722539],
          [20.46937043833673, 68.89159582156138]]], null, false),<br />
    s2H = ee.ImageCollection("COPERNICUS/S2_SR_HARMONIZED");

//Cloud masking function using QA image<br />
// Adapted form http://www.gisandbeers.com/generar-imagenes-satelite-sin-nubes/<br />
function mask_sentinel2(image) {<br />
  var qa = image.select('QA60');<br />
//exclude opaque and cirrus clouds from image<br />
  var opaque  = 1 << 10;<br />
  var cirrus = 1 << 11;<br />
  var mask = qa.bitwiseAnd(opaque).eq(0)<br />
      .and(qa.bitwiseAnd(cirrus).eq(0));<br />
  return image.updateMask(mask);<br />
}<br />
  <br />
//Center on the study area<br />
Map.setCenter(19.84, 68.68, 8); <br />
<br />
// Select all images within the aoi with specified cloud % (per scene), year and month range<br />
    var sdata = s2H.filterBounds(aoi)<br />
                  .filterMetadata('CLOUDY_PIXEL_PERCENTAGE', 'less_than', 20)<br />
                  .filterDate('2017-07-01','2022-09-30')<br />
                  .filter(ee.Filter.calendarRange(7,9,'month'));<br />
<br />
// Print collection to the Console to check number of images, dates etc<br />
print(sdata); <br />

//Mask clouds in the data and print masked collection to the console <br />
var sdata_masked = sdata.map(mask_sentinel2);<br />
print(sdata_masked);<br />

//The following displays all images in true colour, it can take a while<br />
function addImage(image) { // display each image in collection in true colour<br />
  var id = image.id;<br />
  var image = ee.Image(image.id)<br />
  Map.addLayer(image.clip (aoi), {bands: ['B4','B3','B2'],min:0, max:12000, gamma:2.4 });<br />
}<br />

sdata_masked.evaluate(function(sdata_masked) {  // use map on client-side<br />
  sdata_masked.features.map(addImage);<br />
});<br />

1 Answer 1

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I would suggest using this tutorial to filter clouds for Sentinel 2 imagery: https://developers.google.com/earth-engine/datasets/catalog/COPERNICUS_S2_CLOUD_PROBABILITY

The QA band of Sentinel 2 masks out of lot of clear imagery as cirrus and misses many obvious clouds.

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    Commented Jul 26, 2022 at 20:14

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