Creating a Digital Elevation Model (DEM) in QGIS: A Step-by-Step Tutorial

QGIS, also known as Quantum GIS, is a free and open-source geographic information system that can be used to create, edit, and visualize spatial data. One of the essential tasks in GIS is creating a Digital Elevation Model (DEM), which is a representation of the earth's surface as an elevation grid. In this tutorial, we will go over the step-by-step process of downloading and creating a DEM in QGIS software.

Step 1: Download DEM data

The first step is to download the DEM data that we will use to create our model. The best source for this data is the United States Geological Survey (USGS) EarthExplorer website, which provides access to free, high-quality DEMs. You will need to create an account to download data.

• Once you have logged in to the EarthExplorer website, follow these steps to download the data:

• Go to the "Data Sets" tab and select "Digital Elevation."
• Select "SRTM" for the source of the data.
• Select the area you want to download by zooming in on the map or entering the coordinates.
• Select the file format and projection you prefer.
• Click "Results" to view the available data.
• Select the dataset you want to download by clicking on the download icon.

Step 2: Import DEM data into QGIS

After downloading the data, we need to import it into QGIS. Follow these steps:

• Open QGIS and go to the "Layer" menu.
• Select "Add Layer" and then "Add Raster Layer."
• Browse to the location where you downloaded the DEM data and select the file.
• Click "Open" to import the data.

Step 3: Create DEM from imported data

Now that we have imported the data, we need to create the DEM. Follow these steps:

• Go to the "Raster" menu and select "Extraction" and then "Contour."
• In the "Contour" dialog box, select the input layer, output file, contour interval, and units.
• Click "Ok" to start the contouring process.
• Once the contouring process is complete, you will see a new layer in the Layers panel, which represents the contours of the DEM.

Step 4: Visualize the DEM

The last step is to visualize the DEM in QGIS. Follow these steps:

• Double-click on the new layer created in Step 3 to open the Layer Properties dialog box.
• Go to the "Symbology" tab and select "Singleband pseudocolor" as the render type.
• Choose the color ramp you prefer.
• Click "Apply" to visualize the DEM.

In conclusion, QGIS is a powerful tool for creating a DEM from DEM data. By following the simple step-by-step tutorial outlined above, you can easily download and create a DEM in QGIS software. With this model, you can gain insights into the earth's surface and use it for various applications, such as flood mapping, urban planning, and environmental analysis.