The Slope (Terrain analysis) tool calculates the slope angle of each raster cell in degrees.

To calculate the slope of the terrain (Fig. 102):

  1. Go to Raster.
  2. Select Terrain analysis.
  3. Choose Slope.
  4. Choose the DEM as the input raster.
  5. Browse for a destination path and save the output raster as “slope”.
  6. Choose the output format to be used from the list (various formats within GDAL).
  7. Click OK.
  8. Adapt the raster symbolization if necessary (Layer Properties > Symbol).

Besides the Terrain analysis tools there is a set of Terrain analysis functions (with even more options) provided by the GDALTools Plugin (Fig. 103): these tools are accessible by menu Raster > Analysis > DEM (Terrain models).

Fig. 102. Calculating slope with QGIS.