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Accessing vector data

Now that you've learned the basics of raster data, let's examine vector data. This is the other fundamental data type which is used in GIS. Let's get some vector data at the top of that srtm layer. From the Browser Panel, we open up the administrative boundaries layer (the one with the shp extension) containing our study area, and the waterways and traffic layers from the OpenStreetMap data. We can also use the Add Vector Layer button from the side toolbar:

If you don't see the points after opening the traffic data, you might have just opened the traffic areas layer. Geofabrik extracts distinguishable areas from lines and points by appending an a to the file name. The traffic_a_free_1.shp file contains polygons related to traffic (for example, parking lots), while the one named traffic_free_1.shp contains points. You can remove obsolete layers by right-clicking them in the Layers Panel and selecting Remove.

Now there are three vector layers with three different icons and representation types on our canvas. These are the three main vector types we can work with:

Points: Points are used to represent single punctual occurrences of phenomena
Lines: Lines are used to show linear features and boundaries
Polygons: Polygons are used to delimit areas

If we zoom around, we can see that unlike the raster layer, these layers do not pixelate. They remain as sharp as on lower zoom levels no matter how far we zoom in. Furthermore, if we use the Identify Features tool and click on a feature, it gets selected. We can see with this that our vector layers consist of arbitrary numbers of points, lines, and irregular shapes:

You can only select features with the Identify Features tool from the selected layer. If you wish to query another type of feature, first select its layer from the Layers Panel .