Bonus: Sentinel-2 Data in Google Earth Engine

Landsat data has a 30 m resolution, up to 15 m resolution with pansharpening. Archaeologists might prefer using Sentinel-2 data, which can have up to a 10 m resolution. The process to import Sentinel-2 data into Google Earth Engine is the same as for Landsat data.

Import Data

Here we assume you have defined a region using the geometry and renamed it to region. Next, we will import Sentinel-2 imagery. Under Search places and datasets…, type Sentinel, and select Harmonized Sentinel-2 MSI: MultiSpectral Instrument, Level-2A (SR) and click the Import button. Change the name of the variable under Imports to sentinel.

The following code will center the map over your point when the code is run.

Map.centerObject(region, 7);

Generate a Cloud Free Composite

Next we will define some variables, including a date range and amount of cloud cover.

var start = '2023-01-01';
var end = '2023-12-31';

var cloud_max = 30;

Imagery will now be filtered to dates within the year 2023 with less than 30% cloud cover using the following code.

Next, filter the imagery by cloud cover, date, region, and apply the offset of 0.0001 to convert to surface reflectance.

var sentinelfiltered = sentinel
  .filterDate(start,end)
  .filterBounds(region)
  .filterMetadata('CLOUDY_PIXEL_PERCENTAGE','less_than',cloud_max);
  
print(sentinelfiltered);

// Function to mask clouds using the Sentinel-2 QA band
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 image.updateMask(mask).divide(10000);
}

//apply cloud mask function and offset function
var sentinel_masked = sentinelfiltered.map(maskS2clouds);
print(sentinel_masked);

Now add the Sentinel-2 composite to the map.

//create Sentinel median composite and display
var composite = sentinel_masked.median().clip(region);
Map.addLayer(composite, {bands: ['B4', 'B3', 'B2'], min: 0, max: 0.15}, 'Sentinel 2 composite');

This composite can now be edited and used the same as the Landsat data from the previous section.