5.1 Map canvas layers and GUI interactions
5.1.1 Interaction with the map canvas
During model setup in the GUI, the QGIS map canvas will be extended with more and more layers that are added by setting model input maps and evaluating model output maps. The user can modify layer legends to its own preferences, because this does not influence the model results. You are also free to add additional layers or remove layers from the QGIS map canvas. Both actions will not affect model results; because the maps that are used in the model are always shown in the text lines in the GUI (see for example the catchment settings in Figure 28). If you select a model input map in the GUI, this map will automatically be added to the QGIS map canvas. If this layer name already existed in the map canvas, then it will be overwritten with the new selected layer.
Map canvas layout
The map canvas is built using several layer groups. At the beginning of each new project the map canvas is empty. The layer groups are built after model map layers have been selected and added to the canvas. The layer group layout is shown below:
Input
General
Climate
Soils
Land-use
Glaciers
Snow
Routing
Output
Annual
Monthly
Daily
An example of this layer group (with layers) layout is shown in Figure 17. The Input layer groups correspond with the GUI tab widgets that need to be completed by the user during Sections 'General sections' through Section 'Visualizing model input'. The Output layer groups are built during the last step of the GUI: Visualize results.
Setting a background layer
As can be seen from figure 17, a Google Physical background has been added to the canvas. Background layers in QGIS, such as the Google Physical background layer, are available as plugins. The Google Physical background layer, together with layers as OpenStreetMap, Bing maps and other Google maps, are part of the OpenLayers plugin. This plugin can be installed and activated in a similar way as the SPHY model plugin was activated. You can search for this plugin by typing google in the search window (Figure 18). Then select the OpenLayersPlugin and click Install plugin and after installation click Close. You are now able to set any background map from the OpenLayersPlugin you like (Figure 19).
It should be noted that setting and viewing a background layer requires an internet connection. Because of the continues connection with internet, the use of background layers may slow down processes such as panning and zooming inside QGIS.
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