EXAMPLE : THE 'R.WATERSHED FUNCTION'
You can see on the picture a map plotted with the 3D visualization tool
NVIZ. This raster map represents a region aroud Mazamet in France (IGN
data), divided into 5 principal watersheds. We will describe how to obtain
such a picture:
The green watershed is the Thoré watershed; the yellow one is the
Banquet watershed, where we can see the Gorges we studied with 'r.profile'
just before. The blue watershed corresponds to the Arnette one. These three
watersheds meet just before Mazamet, and the third one (in pink) represents
the watershed down Mazamet. These watersheds are in the Atlantic basin,
while the grey one (at the top of the map, close to Saint-Pons) is in the
Using Grass5 zoom (d.zoom), we choose a region around Mazamet on the raster
Then, using 'manage.region', we choose to work only on the raster region
we have zoomed on.
We launch the 'r.watershed' functionality to cut this region into several
Using 'r.reclass', we keep only the interesting watersheds in the display
We display the streams vector map on the raster one (d.vect).
Eventually, we open NVIZ to visualize the resulting map in 3D.
The conference menu - Getting
information - GIS market - Grass
anatomy - r.profile function - r.watershed
function - Computed waterlines - Screenshots