Google Earth Engine Tutorial: Download SRTM DEM Data

Google Earth Engine Tutorial: Download SRTM DEM Data

Google Earth Engine (GEE) is a powerful platform for geospatial analysis and data access. One of its key features is the ability to retrieve high-resolution Digital Elevation Models (DEMs), such as the Shuttle Radar Topography Mission (SRTM) dataset. This tutorial demonstrates how to use GEE to download SRTM DEM data in various formats.

Step-by-Step Guide

1. Access Google Earth Engine Console

Log in to the Google Earth Engine Console using your Google account. Ensure you have the correct permissions and access to the SRTM dataset.

2. Open the Code Editor

Navigate to the Code Editor section. This will provide an interface to write and run JavaScript or Python scripts.

3. Load the SRTM DEM Dataset

Use the following code snippet to load the SRTM dataset:

var srtm = ee.Image("USGS/SRTM90_V4");

This loads the SRTM 90-meter elevation data. Adjust the dataset name if you need a different version (e.g., “NASA/JPL/SRTMGL1_SRTM_DEPTH” for depth data).

4. Define the Region of Interest (ROI)

Specify your area of interest using a geometry or by clicking on the map. For example:

var roi = ee.Geometry.Rectangle([x1, y1, x2, y2]); // Replace with your coordinates

You can also use the interactive map tools to draw a region and retrieve its coordinates.

5. Clip the Dataset to Your ROI

Clip the DEM to your defined region:

var clipped = srtm.clip(roi);

This ensures the data extracted is relevant to your specific area.

6. Export the Data

Export the clipped image to your Google Drive or other storage. Use the following code:

Export.image.toDrive({
  image: clipped,
  description: 'SRTM_DEM_Export',
  folder: 'GEE_Exports',
  scale: 90,
  region: roi,
  maxPixels: 1e10
});

Adjust scale for resolution, region for the area, and maxPixels to avoid errors for large regions.

7. Monitor the Export

Check the Tasks tab in the Code Editor to monitor the export progress. Once completed, download the file from your Google Drive.

For bulk downloads or specific formats (e.g., GeoTIFF, ASCII), modify the export parameters accordingly:

Export.image.toDrive({
  image: clipped,
  description: 'SRTM_DEM_Export',
  folder: 'GEE_Exports',
  scale: 90,
  region: roi,
  maxPixels: 1e10,
  fileFormat: 'GeoTIFF' // or 'AAIGRID' for ASCII
});

Frequently Asked Questions (FAQ)