The Aspect (Terrain analysis) tool uses a DEM to calculate the direction in which slopes are facing (see section 18.104.22.168. for more information).To calculate the aspect based on a DEM:
- Go to Raster.
- Select Analysis.
- Choose DEM (Terrain models).
- Choose the mode Aspect (Fig. 103) (the function Raster > Terrain analysis > Aspect is just another option to achieve the same result).
- Select the DEM as the input raster.
- Browse for a destination path to save the output raster as ASTER30_aspect_CH1903.tif.
- Some optional settings can be activated or deactivated in the checkboxes, to make flat areas (that do not have a valid aspect value by default) zero values, for instance.
- Click OK.
- Adapt the raster symbolization if necessary (Layer Properties > Symbol).
Fig. 103. Calculating aspect with QGIS.