7.8.3. Example 3: Computing intersections between a DEM and planes

GIS is very useful for applications in natural sciences and a variety of tools are provided, e.g. for visibility analysis or to delimit watersheds, calculate flow paths, or even simulate natural hazards. This example demonstrates a very specific function, based on the qgSurf plugin for QGIS:

  1. Load and activate the plugin qgSurf (see section 7.1.3.).
  2. Go to Plugins.
  3. Select qgSurf.
  4. Select the DEM ASTER30_dem_CH1903 and choose source point for the plane (e.g. around Fribourg 578000/183000/627).
  5. Play around with the values for orientation and inclination of the plane and calculate the intersections (Fig. 108).
  6. Save the output as point or line shapefile.

To analyse spatially related processes in more detail or for modelling, functions within GRASS GIS (http://grass.osgeo.org, Neteler and Mitasova, 2008) or SAGA (http://www.saga-gis.org) can be useful. To access these, GRASS and/or SAGA have to be installed on your computer and within QGIS the SEXTANTE Toolbox plugin (http://plugins.qgis.org/plugins/sextante) needs to be installed and configured correctly (see QGIS Development Team, 2013). If you work with R, the plugin Spatial Data Analysis for Point Pattern (SDA4PP) might also be a good option (see section 7.1.3.).

Fig. 108. Spatial analysis computing the intersection between a DEM and an inclined plane with the QGIS plugin qgSurf.