QGIS understands three major forms of data. Two of these are spatial (ie, they contain information allows it to be shown in space) and the third contains no spatial data ("aspatial data")The two spatial data types are:
- Vector data. Vector data can be drawn by lines of varying lengths; that is points, lines or polygons. In QGIS a single vector layer can only contain one of these three geometry types.
- Raster data. These are images, jpg, tif, etc. These files should be accompanied by or contain information that allows them to be shown in the correct location.
This technical note shows a process for adding a vector layer to your QGIS project --- and it's easy.
Plugins : None
Click on the Add Vector Layer button
Fill in the box.
A completed dialogue box that will open the Alaska shape file
You can use the browse button to locate your file, and once selected use the open button to return to the the main dialogue box.
Browsing to the Alaska shape file
Once everything is filled in on the main dialogue, just hit open and you're done.
The Alaska shape file
- You can also open a vector layer using Layer → Add vector layer or the keyboard shortcut.
- QGIS believes that vector files should only contain point or line or polygon data. Mapinfo users take note.
- As of 1.8 GIS will place a new layer in the TOC above any layer you have selected. In this example Alaska is selected, so a new layer would be placed above the Alaska layer.
- By default QGIS looks for shape files (*.shp). Many other file types can also be opened too, including mapinfo tab files. A full list may be found at http://www.gdal.org/ogr/ogr_formats.html . You can filter for different file types in the browse dialogue box.
- Be very aware of projections. Vector files are not required to provide projection information (e.g. a *.prj file). If QGIS is unsure about what projection to display a file it defaults to opening the file in the default projection - WGS84.
- If a file is opened in the wrong projection, this can be changed. Right click on the relevant layer, and choose "Set layer CRS".
- Both the default for what to do when QGIS doesn't know the projection and the default projection can be changed.