HOW TO DOWNLOAD DIGITAL ELEVATION MODEL(DEM) OF YOUR AREA OF INTEREST USING GOOGLE EARTH ENGINE

Want to elevate your chances of finding a digital elevation model (DEM) data?

Sure you do.

Let’s dive into our list of more about DEM…..

By; Maina Njuguna , PETER NDIRITU THUKU , Thitai Francis ndiritu

What is (DEM):

A Digital Elevation Model (DEM) is a representation of the bare ground (bare earth) topographic surface of the Earth excluding trees, buildings, and any other surface objects. In the old days DEM used to be generated from topographical maps but of late with the recent advancement in technology, DEMs derived from high-resolution lidar data

Where to get(DEM):

1. USGS Earth explorer …. https://earthexplorer.usgs.gov/
2. Open Topography….https://portal.opentopography.org/raster?opentopoID=OTSRTM.082015.4326.1
3. Google earth engine ……. https://earthengine.google.com/platform
4. From Drone imagery — AgiSoft Processing.
5. You can also generate yours with kml /kmz data collected from Google Earth Pro.

USGS interface

In Google Earth Engine alias GEE,for you to download (DEM) you need to follow the following steps:

1. Navigate to your browser and search for Google Earth Engine
2. Go to platform, then select code editor. This is where you write your codes for the Engine to excute.
3. Select your area of interest using the polygon tool or import your shapefile of your interest.
4. Import the DEM data set by searching on SRTM data and then import it
5. Export your data to your Google drive where you can access it in your Pc

Let’s get started Champs…

// import srtm data and clip to your ROI
var image =ee.Image(“USGS/SRTMGL1_003”).clip(ROI);
// Add your layer for visualization
Map.addLayer(image,{min:-50,max:3000},’019');
Map.centerObject(ROI,9);
// Export to your Drive
Export.image.toDrive({
image:image,
description: ‘019 DEM’,
folder: ‘earthengine’,
fileNamePrefix: ‘019DEMclip’,
region: ROI,
scale: 30,
maxPixels: 1e13})

*** Typo errors, Syntax errors would make your code not RUN thus not achieving your output***

Click on the RUN button for you to export your (DEM) to your Google Drive

After downloading your (DEM) you load the on other GIS and remote sensing software such as ArcMap ,QGIS ,ArcGIS Pro, or Envi for further analysis.

FAQ: What are digital elevation(DEM) models used for?

1.Modeling water flow for hydrology or mass movement.

2. Base mapping

3.Terrain analysis

4.Creation of relief maps

5.Rendering of 3D visualization

6.Extracting terrain parameters for geomorphology

7.Modelling water flow for hydrology or mass movement

8.Modelling soils wetness with Cartographic Depth to Water Indexes.

9.Used in Highway construction & Highway interchanges , for generation of contours.

10.Last but not least its used in EIA among other applications.

Thanks for reading through , incase of any clarity reach out me for more here;

Email me : njugunamaina28@gmail.com

Twitter: @maina_maps

Tel : +254723 144789

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