Cloud Masking for Landsat 8 (LANDSAT/LC08/C02/T1_L2) in Google Earth Engine

Question

I am trying to mask clouds in Landsat 8 surface reflectance imagery but I am getting a white output (Left image below) - the expected imagery is on the right.

Below are the lines of code.

var image = ee.ImageCollection('LANDSAT/LC08/C02/T1_L2')
   .filterBounds(CCmaine);

function maskL8sr(image) {
  var cloudShadowBitMask = (1 << 4);
  var cloudsBitMask = (1 << 3);

  var qa = image.select('QA_PIXEL');

  var mask = qa.bitwiseAnd(cloudShadowBitMask).eq(0)
             .and(qa.bitwiseAnd(cloudsBitMask).eq(0));

  return image.updateMask(mask).divide(10000)
              .select("SR_B[0-9]*")
              .copyProperties(image, ["system:time_start"]);
}

var sum20 = ee.Filter.date('2020-06-01','2020-09-30');
var sum19 = ee.Filter.date('2019-06-01','2019-09-30'); //Note the date adjustment

var SumFilter = ee.Filter.or(sum20, sum19);
var allsum = image.filter(SumFilter);

var composite = allsum
              .map(maskL8sr)
              .median()
              .clip(CCmaine);

Map.addLayer(composite, {bands: ['SR_B4','SR_B3','SR_B2'],min:0, max:0.3},'Cumberland Color Image', 0);

Looking forward to your help!

Answer 1

Landsat collection 2 images aren't simply scaled by 0.00001. The optical bands are scaled by 0.0000275 and have an offset of -0.2 (the thermal bands are different). This is demonstrated in the code editor examples (Examples > Cloud Masking > Landsat8 Surface Reflectance). In your code, it'd be:

return image.updateMask(mask).multiply(0.0000275).add(-0.2)