Viewing data in QGIS

When you start QGIS it opens a new blank project, into which you can add your data and work on it.

The interface consists of a number of toolbars across the top and down the left hand side, a Layer control panel on the left with a Browser panel beneath; the main map window occupies the majority of the space in the interface with coordinate information displayed along the bottom.

Adding Vector Data

1. To add vector data to the map window use the 'Add Vector Layer...' command from the Layer menu or use the 'Add Vector Layer' button in the Manage Layers toolbar on the left hand side.
   
2. In the Add Vector Layer dialog select an appropriate 'Source type' and browse to the dataset(s) you wish to add. The Encoding can be left as System as this will be set automatically by QGIS when importing the file.
   
   The table below describes the common Source Types:
   

   Source type	Explanation
   File	Use for most geographic file formats including Shapefile, GML and GPX
   Directory	Use for ESRI file geodatabases
   Database	Use for ESRI personal geodatabases
   Protocol	Use for GeoJSON

3. If the file contains data for more than one layer you will be given the choice of which layers you wish to display. Use the 'Select All' button to add all layers from the file.
   
4. The data will be displayed using default colours applied by QGIS for each layer:
   

Information on applying style files is available.

Adding Raster Data

1. To add raster data to the map window use the 'Add Raster Layer...' command from the Layer menu or use the 'Add Raster Layer' button in the Manage Layers toolbar on the left hand side.
   
2. The open raster dataset dialog will open, browse to your dataset and press the Open button.
3. The data will be displayed in the map window.

Overlaying Raster and Vector data

It can be useful to show both raster and vector data in the same map window, for example to give locational context to bedrock geology data. In QGIS it is easy to convert raster images to greyscale, then make them transparent so that any coloured vector layers are visible beneath the raster image. The steps below outline this process.

1. Start by adding your vector dataset to QGIS and setting appropriate symbology either by creating the style required or by applying existing style files.
2. Add the raster data that you wish to use for background information to the QGIS project and ensure it is above the vector data in the Layer panel.
3. Open the properties of the raster dataset and go to the Style tabe.
4. Set the 'Render type' to 'Singleband gray'; this will display the raster in greyscale:
   
5. Go to the Transparency tab and set the 'Global transparency' to 50%:
   
6. This will ensure the raster image is transparent and that the data below can be seen through:
   
   The image above shows 1:50,000 Scale Geology Data with OS VectorMap® Local Raster on top displayed in greyscale with 50% transparency.