TRD 05: Data Presentation techniques (Mapping) Quantum GIS ...

4.5 Editing
Snap Mode
QGIS allows digitised vertices to be snapped to other vertices of the same layer. To set the snapping
tolerance, go to Settings->Project Properties->General->Snapping Tolerance. Note that the snapping
tolerance is in map units.
Saving Edited Layers
When a layer is in editing mode, any changes remain in the memory of QGIS. Therefore they are
not committed/saved immediately to the data source or disk. When you turn editing mode off (or quit
QGIS for that matter), you are then asked if you want to save your changes or discard them.
If the changes cannot be saved (e.g. disk full, or the attributes have values that are out of range), the
QGIS in-memory state is preserved. This allows you to adjust your edits and try again.
4.5.2. Creating a New Layer
To create a new layer for editing, choose New Vector Layer from the Layer menu. The New Vector
Layer dialog will be displayed as shown in Figure 7. Choose the type of layer (point, line, or polygon).
Figure 7: Creating a New Vector Dialog
Note that QGIS does not yet support creation of 2.5D features (i.e. features with X,Y,Z coordinates) or
measure features. At this time, only shapefiles can be created. In a future version of QGIS, creation
of any OGR or PostgreSQL layer type will be supported.
Creation of GRASS-layers is supported within the GRASS-plugin. Please refer to section 8.7 for
more information on creating GRASS vector layers.
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