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I have tried to apply a cloud mask for a landsat 8 collection using code1, code2, and code3 but none will work.

code1 encounters the error of not working even after changing

var mask = img.select(['cfmask']).neq(4) to

var mask = img.select(['pizel_qa_bands']).neq(3)

code2 encounters the problem of not being a time series dataset. I want to be able to extract pixel values for each image over a period of time but this code only gives one output of pixel values.

and I can't adapt my script to code3.

Here is my script and all i want to do is remove the clouds and cloud cover from a Landsat8 image collection

var l8_mayo = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA')
  .filterDate('2000-01-01', '2018-12-31')
  .filter(ee.Filter.eq('WRS_PATH', 208))
  .filter(ee.Filter.eq('WRS_ROW', 23));

var visParams = {bands: ['B4', 'B3', 'B2'], max: 0.3};
Map.setCenter(-9, 53, 8);
Map.addLayer(l8_mayo, visParams, 'l8_mayo collection');`

marked as duplicate by Kersten, nmtoken, whyzar, BERA, tinlyx Mar 13 '18 at 18:55

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • There is no cloud mask included in the Top-of-Athmosphere TOA product. Have you tried the Surface Reflectance SR collection with its associated quality band and cloud masks? – Kersten Mar 13 '18 at 17:01
  • The above link encounters the problem of not being a time series dataset. I can't extract pixel values for each image over a period of time. – Walshe_d Mar 13 '18 at 17:29
  • Working with a time series just entails using .map() to apply the function to each image within the collection. – Kersten Mar 13 '18 at 18:16
1

code2 works. Adapt it properly with right parameters (Always check metadata):

var l8_mayo = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA')
  .filterDate('2000-01-01', '2018-12-31')
  .filter(ee.Filter.eq('WRS_PATH', 208))
  .filter(ee.Filter.eq('WRS_ROW', 23));

var visParams = {bands: ['B4', 'B3', 'B2'], max: 0.3};
Map.setCenter(-9, 53, 8);
Map.addLayer(l8_mayo, visParams, 'l8_mayo collection');

var getQABits = function(image, start, end, newName) {
    // Compute the bits we need to extract.
    var pattern = 0;
    for (var i = start; i <= end; i++) {
       pattern += Math.pow(2, i);
    }
    // Return a single band image of the extracted QA bits, giving the band
    // a new name.
    return image.select([0], [newName])
                  .bitwiseAnd(pattern)
                  .rightShift(start);
};

// A function to mask out cloudy pixels.
var cloud_shadows = function(image) {
  // Select the QA band.
  var QA = image.select(['BQA']);
  // Get the internal_cloud_algorithm_flag bit.
  return getQABits(QA, 7,8, 'Cloud_shadows').eq(1);
  // Return an image masking out cloudy areas.
};

// A function to mask out cloudy pixels.
var clouds = function(image) {
  // Select the QA band.
  var QA = image.select(['BQA']);
  // Get the internal_cloud_algorithm_flag bit.
  return getQABits(QA, 4,4, 'Cloud').eq(0);
  // Return an image masking out cloudy areas.
};

var maskClouds = function(image) {
  var cs = cloud_shadows(image);
  var c = clouds(image);
  image = image.updateMask(cs);
  return image.updateMask(c);
};

var l8_mayo_free = l8_mayo.map(maskClouds);

Map.addLayer(l8_mayo_free, visParams, 'l8_mayo collection without clouds');

Link: https://code.earthengine.google.com/44cb99f8210800462da56640a275e674

There are some areas with cloud borders in image collection. Is a very cloudy area. BQA isn't perfect

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