Demo 20 - Intro to Raster Data (Part 2) - Digital Elevation Models and the Raster Calculator

In this follow-up QGIS tutorial on raster data, we’ll explore common tools and derivatives of digital elevation models (DEMs) and show how to use the Raster Calculator to select and combine rasters. Follow along as we generate Slope, Hillshade and Aspect rasters, demonstrating their parameters and applications in analyzing and visualizing 3D terrain characteristics. We’ll also elaborate on raster visualization, showing how to create pseudo and actual 3D views. In addition, we’ll learn how to use the Raster Calculator, first to query and select cells from a raster by criterion of interest, and then to combine multiple rasters. Finally, we’ll use the Contour lines tool to extract line vectors of equal value from the merged DEM. The procedures and skills covered in the tutorial are essential for extracting and conducting a wide variety of analyses and visualizations for DEMs and related datasets-which influence various socioeconomic and biophysical processes-as well as raster datasets more broadly. Apply these skills, such as using the Raster Calculator to query and combine relevant rasters, to generate an array of fine-resolution datasets and perform related analyses.
Link to the National Research Council of Canada’s Sunrise/sunset calculator:
nrc.canada.ca/en/research-dev....
The final component of the demo shows additional outputs that can be generated with various raster tools, including r.viewshed (to show visible areas from a selected point) and r.walk.points (to create a cumulative cost raster for least-cost path analysis with raster data). The latter requires creating start and end points and a friction raster, dictating the costs of moving between cells. The friction raster is created by reclassifying and combining land-cover classes in the Annual Crop Inventory with the Slope raster (similar to the weighted combination of Slope and Aspect shown in the video).