7.9.4. Raster layer styling and predefined colour maps
The layer CLC06_Fribourg.tif is now quite handy for our purpose, but so far we do not know for what the numbers (raster values) stand for (see Fig. 111). Luckily, a colour map is provided by the European Environment Agency (EEA) and can be loaded into QGIS (similar to the ArcGIS layer file, see section 6.9.4. for more information):
- Double-click on the layer CLC06_Fribourg in the Map Legend to open its Layer Properties.
- Navigate to the Tab Colormap and Click the Symbol Load color map from file.
- Navigate to the folder that you have unzipped in step 2 (e.g. CORINE_2006_100m), select the text file clc_legend_qgis.txt and click Open.
- Click Apply (see Fig. 112)
and close the Layer Properties with OK.
Note that the raster values do not correspond with the numbers
(categories) indicated in the labels (Fig. 112). You can verify this by using
the Identify Features button and comparing this with the
entries in the Map Legend. This might be a little confusing, but the reason is
of technical nature: the official CLC06 land cover category numbers (50 in total)
ranging from 111 to 999 cannot be displayed with a single band 8-bit integer
raster dataset, where the range of raster values is limited to 0-255. Of course
a 32-bit floating-point raster image could be used to display the whole range
from 111 to 999, but then the dataset would become almost 4 times larger and
unhandy for download, storage and analysis. In the following tasks we will make
use of numbers written in the labels of CLC06_Fribourg.tif.
Fig. 112. Setting the Colourmap for the CORINE Land Cover 2006 data: For each integer value of the raster image a colour and a label is assigned.