I inherited a clipped (500m radius) land cover map containing vector layers of different land cover categories such as buildings, grass, roads, etc from a colleague.
The empty (white) space in the map is actually paved surfaces in reality but is it possible to fill that "empty space" with another vector layer that creates a new landcover polygon class automatically? I'm under the impression that it is possible to create another layer with the symmetrical difference tool but I think I need two input vector files - the one with all the current layers and another layer. Am I supposed to create another vector layer that covers the exact same area (i.e. 500 m radius about a certain point?) and how do I go about doing that?
To summarize, this is what I did to get the difference layer:
- Add a vector layer with center-point to existing maps.
- Create a buffer layer using this centerpoint. Vector > Geoprocessing tools > Buffer. Use the new vector layer with center-point as input layer.
- With the new buffer layer, you can now use the Difference Tool (Vector > Geoprocessing > Difference). Use the buffer layer as your input layer, and the other layer being your main map.
- You will have to edit the attributes of the new layer so it corresponds to the same type of attributes in your base map.
- Merge the layers using the mmqgis tool (mmqgis > transfer > merge layers), and create a new shapefile with all the layers merged together.