Cloud filtering Landsat collection 2 over specific regions

Question

I'm trying to filter clouds over a specific region for an NDVI time series using Landsat collection 2.

I tried filtering with simple cloud score but it doesn't seem to work (maybe because there is no simpleCloudScore?).

Here's part of my full code:

var extent = 
    /* color: #44c239 */
    /* displayProperties: [
      {
        "type": "rectangle"
      }
    ] */
    ee.Geometry.Polygon(
        [[[35.66951628813774, 33.212344469176244],
          [35.66951628813774, 33.18720738523013],
          [35.69560881743462, 33.18720738523013],
          [35.69560881743462, 33.212344469176244]]], null, false);
          
// Applies scaling factors for LS 457.
function applyScaleFactors457(image) {
  var opticalBands = image.select('SR_B.').multiply(0.0000275).add(-0.2);
  var thermalBand = image.select('ST_B6').multiply(0.00341802).add(149.0);
  return image.addBands(opticalBands, null, true)
              .addBands(thermalBand, null, true);
}

var startdate = '2000-08-01';
var enddate= '2021-08-01';

var LS7Collection = ee.ImageCollection('LANDSAT/LE07/C02/T1_L2')
  .filterBounds(extent)
  .filterDate(startdate, enddate)
  .map(applyScaleFactors457);

//filer clouds by region ????
var c = LS7Collection.filterBounds(extent);

var withCloudiness = c.map(function(image) {
  var cloud = ee.Algorithms.Landsat.simpleCloudScore(image).select('cloud');
  var cloudiness = cloud.reduceRegion({
    reducer: 'mean', 
    geometry: extent, 
    scale: 30,
  });
  return image.set(cloudiness);
});

var LS7Collection = withCloudiness.filter(ee.Filter.eq('cloud', 0));
print(LS7Collection);

Link to the full code: https://code.earthengine.google.com/?scriptPath=users%2Ftomcol%2Fpersonal%3ANDVI%20SERIES%20LANDSAT%207

Answer 1

ee.Algorithms.Landsat.simpleCloudScore() won't work because the input for this algorithm is a TOA image:

Arguments:

- image (Image): The Landsat TOA image to process.

Since your product is SR, you can use SR_CLOUD_QA (bitmask):

• Bit 0: Dark Dense Vegetation (DDV)
• Bit 1: Cloud
• Bit 2: Cloud Shadow
• Bit 3: Adjacent to Cloud
• Bit 4: Snow
• Bit 5: Water

This layer will help you to define the cloud

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);
};

var clouds = function(image) {
  // Select the QA band.
  var QA = image.select(['SR_CLOUD_QA']);
  // Get the internal_cloud_algorithm_flag bit.
  return getQABits(QA, 1,1, 'Clouds').eq(1);
};

Full example code for one cloudy date: https://code.earthengine.google.com/46592b18ddb7ed11b4986f2f0698d70f