Pansharpened Landsat 8 Mosaic

This script processes Landsat 8 satellite images to create pansharpened mosaics for a specific region and time period. It utilizes Google Earth Engine (GEE) functionalities to filter, mask, and enhance satellite images for visualization and export. The script is designed to maintain natural colors for visualization and analysis.

Features

• Region of Interest:
  • Defines a 3 km x 3 km rectangle around a specified center point.
• Cloud Masking:
  • Applies a cloud mask using the QA_PIXEL band to ensure minimal cloud cover.
• Pan-Sharpening:
  • Enhances RGB bands using the panchromatic band via HSV transformation.
  • Maintains natural color appearance (e.g., vegetation appears green).
• Annual Mosaic Generation:
  • Creates annual mosaics for a list of specified years.
• Export Functionality:
  • Exports pansharpened mosaics as high-resolution images to Google Drive.

Study Case

Lumpur Lapindo refers to the devastating mudflow disaster that began in May 2006 in Sidoarjo, Indonesia. Caused by a combination of drilling activities and geological factors, the mudflow has displaced thousands of residents and created an ongoing environmental and social crisis.

In this code, the Lumpur Lapindo study case in Sidoarjo, Indonesia, is analyzed from 2020 to 2024, with annual pansharpened mosaics generated for each year.

Script Overview

1. Define Region of Interest

The center point and rectangle for the region of interest are defined:

var center = ee.Geometry.Point([112.7059683, -7.5244837]);
var rectangle = center.buffer(3000).bounds();

2. Cloud Masking

Clouds are masked using the QA_PIXEL band:

var maskL8 = function(image) {
  var qa = image.select('QA_PIXEL');
  var mask = qa.bitwiseAnd(1 << 3).eq(0); // Bit 3 for cloud
  return image.updateMask(mask);
};

3. Pan-Sharpening

RGB bands are enhanced using the panchromatic band:

var panSharpenL8 = function(image) {
  var rgb = image.select('B4', 'B3', 'B2');
  var pan = image.select('B8');
  var huesat = rgb.rgbToHsv().select('hue', 'saturation');
  var pansharpenedRgb = ee.Image.cat(huesat, pan).hsvToRgb();
  return image.addBands(pansharpenedRgb.rename(['B4_ps', 'B3_ps', 'B2_ps']), null, true);
};

4. Mosaic Generation

Filters and processes Landsat 8 images to create annual mosaics:

function getMosaic(year) {
  var startDate = ee.Date.fromYMD(year, 1, 1);
  var endDate = ee.Date.fromYMD(year, 12, 31);

  var landsatCollection = ee.ImageCollection('LANDSAT/LC08/C02/T1_TOA')
    .filterBounds(rectangle)
    .filterDate(startDate, endDate)
    .filter(ee.Filter.lt('CLOUD_COVER', 20))
    .map(maskL8)
    .map(panSharpenL8);

  var mosaic = landsatCollection.median().clip(rectangle);
  return mosaic;
}

5. Visualization and Export

Processes multiple years, visualizes the results on the map, and exports them to Google Drive:

var years = [2020, 2021, 2022, 2023, 2024];
years.forEach(function(year) {
  var mosaic = getMosaic(year);
  Map.addLayer(mosaic, {bands: ['B4_ps', 'B3_ps', 'B2_ps'], min: 0.02, max: 0.25, gamma: 1.2}, 'Pansharpened Natural Mosaic ' + year);

  Export.image.toDrive({
    image: mosaic.visualize({bands: ['B4_ps', 'B3_ps', 'B2_ps'], min: 0.02, max: 0.25, gamma: 1.2}),
    description: 'Natural_Pansharpened_Landsat8_Mosaic_' + year,
    folder: 'Lapindo',
    fileNamePrefix: 'Natural_Pansharpened_Landsat8_Mosaic_' + year,
    region: rectangle,
    scale: 15,
    crs: 'EPSG:4326'
  });
});

6. Map Centering and Boundary Display

Centers the map and highlights the rectangle:

Map.centerObject(rectangle, 13);
Map.addLayer(rectangle, {color: 'red'}, 'Rectangle');

Usage

1. Open the script in the Google Earth Engine Code Editor.
2. Modify the center coordinates and years as needed.
3. Run the script to generate and export pansharpened mosaics to your Google Drive.

Requirements

• Google Earth Engine account.
• Access to the Landsat 8 TOA image collection (LANDSAT/LC08/C02/T1_TOA).

Output

• High-resolution pansharpened mosaics exported to a folder named Lapindo in Google Drive.
• Visualizations of annual mosaics in the Google Earth Engine Map interface.

Notes

• The script uses a 15-meter resolution for pansharpened exports.
• Ensure the Google Drive folder Lapindo exists, or adjust the folder name in the script.

License

This script is provided for educational and research purposes. Use at your own discretion.