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Terrain Profile

Learn how to extract an elevation profile along a drawn transect using the Profile Tool.

Prerequisites​

  • A DEM raster loaded in the active GRASS environment
  • Completed Your First Analysis (optional but recommended)

1. Open the Profile Tool​

Click the Profile toolbar button (bar-chart icon with circle border). The Profile Tool panel appears in the left sidebar.

2. Select the DEM​

Choose your elevation raster from the Input raster dropdown.

3. Set resolution (optional)​

Leave Resolution blank to use the current region resolution, or type a value (in map units) for a finer/coarser sample.

4. Draw the transect​

  1. Click Draw Line — a hint appears: Click the map to add waypoints. Double-click to finish.
  2. Click on the Cesium globe to place the start point
  3. Continue clicking to add intermediate waypoints
  4. Double-click on the final point to finish

The transect appears as a cyan polyline on the globe.

5. Run the profile​

Click ✓ Done. The tool calls r.profile and displays the result chart below the globe.

Once the profile data arrives the cyan polyline is replaced by a vertical wall curtain (semi-transparent orange, red outline) whose top edge follows the actual terrain elevation. The wall is visible from any camera angle.

6. Read the chart​

  • X axis — cumulative distance along the transect (metres)
  • Y axis — raster value at each sample point (elevation in map units)
  • Hover over the chart to read exact values
  • Scroll to zoom in; drag to pan

7. Re-run with a different raster​

Change the Input raster selection and click ↺ Re-run in the chart toolbar to update the profile without redrawing the line.

8. Clear the transect​

Click ✕ Clear to remove the line and reset the tool.

:::tip Session persistence The transect waypoints and chart are saved in the workspace autosave. When you return to the page the line and chart are restored without re-running the module. :::