Lab 5 - Challenge: Refreshers

Objective: Practice creating natural color and false color composites independently.

Before you start

  • Prerequisites: Complete Labs 1–4 and gather your notes on study area selection from the earlier challenges.
  • Estimated time: 75 minutes
  • Materials: Earth Engine login, any saved scripts from prior labs, and supporting references for your chosen region.

Introduction

This challenge lab gives you the opportunity to practice the skills you've learned in the previous labs. You'll work with a specific Landsat image to create both natural color and near-infrared false color composites, then analyze what each reveals about an environmental event.

Challenge Task

Create a new script to make two composites - natural color and near-infrared false color for this image:

Image ID:

'LANDSAT/LT05/C02/T1_L2/LT05_022039_20050907'

In your script, make comments with the following information:

  • Where is this image?
  • What environmental event do you think the images show?
  • Compare and contrast the natural and false-color composites.
  • What do the false-color composite help you see that is more difficult to decipher in the natural color composite?

Hints

Remember:

  • Landsat 5 uses Collection 2 Level 2 data
  • Natural color composite: Use bands SR_B3 (Red), SR_B2 (Green), SR_B1 (Blue)
  • False color (NIR) composite: Use bands SR_B4 (NIR), SR_B3 (Red), SR_B2 (Green)
  • You may need to adjust min/max values for optimal visualization
  • Use Map.centerObject() to center on the image
  • Scale factors for Landsat Collection 2 Level 2: multiply by 0.0000275 and add -0.2

Sample Code Structure

// Load the image
var image = ee.Image('LANDSAT/LT05/C02/T1_L2/LT05_022039_20050907');

// Apply scaling factors
function applyScaleFactors(image) {
  var opticalBands = image.select('SR_B.').multiply(0.0000275).add(-0.2);
  return image.addBands(opticalBands, null, true);
}

var scaledImage = applyScaleFactors(image);

// Center the map
Map.centerObject(image, 8);

// Create natural color composite
// YOUR CODE HERE

// Create false color composite
// YOUR CODE HERE

Analysis Questions

After creating your composites, explore the image and answer these questions in your script comments:

  1. Location: Where is this image located? (Hint: Look at the path/row and use geographic features)
  2. Environmental Event: What type of environmental event or phenomenon do you observe? Look for clues in both the natural and false color composites.
  3. Comparison: How do the natural color and false color composites differ in what they reveal? Which features are more prominent in each?
  4. False Color Advantage: What specific information does the false color composite reveal that is harder to see in the natural color composite?

📧 Lab Submission

Submit lab via email.

Subject: Lab 5 - Challenge Refreshers - [Your Name]

Submit:

A shareable URL to your Google Earth Engine script that includes:

  • Code to create both natural color and false color composites
  • Comments answering all four questions above
  • Proper visualization parameters for both layers
  • Descriptive layer names

Total: 50 Points