Using QGIS (3) – More Layer Symbology

September 23rd, 2007

This post continues a look at the basics of GIS using the mapping program Quantum GIS (QGIS). We’ve already covered how to install and use QGIS in a previous post. In addition, we also introduced shapefiles, including how to download and use them in QGIS. Before moving on to another topic, it is worth demonstrating another example of downloading a shapefile and setting up it’s symbology in QGIS.

Data Download

Shapefiles generally come in three types – points, lines, and polygons. Our previous examples have used line shapefiles but this time we will download a polygon shapefile. For example, we downloaded a countries of the world shapefile found here that looks like this when loaded into QGIS:

Countries of the World Shapefile

Layer Symbology

To make the map more colorful, right-click on the layer name and select Properties. Under the Symbology tab, select Unique Value as the Legend Type and chose Name as the Classification Field. Each country polygon is then randomly assigned a color after pressing Ok.

Countries of the World Shapefile

Labeling

We’ve avoided the topic of labeling so far because QGIS has limited labeling capabilities (improved labeling is coming in future releases). If you go back to the Layer’s properties, select the Labels tab, and then check the box to display labels, the map looks something like this:

Countries with Labels

Zooming in closer reduces some of the overlap but country names are displayed several times if the country has multiple polygon shapes. It is possible to generate label placement positions in other programs and then use them in QGIS but that process is more complex and isn’t really relevant to our objectives. Labeling aside, QGIS is still a free and easy-to-use GIS program that will help us compile data for our own mapping applications.

Next time will we introduce raster images and how to use them in QGIS.

Continue to part 4