Adding a scale bar to the map

A scale bar is one of the most important elements of a map composition, as it defines the scale of the map to determine the ground distance on the map. QGIS composer allows you to create several different types of scale bars from a simple text scale ratio to a graphical, double scale bar with two measurement systems. In this recipe, we'll create a scale bar that measures in kilometres.

Getting ready

You will need to download the following zipped shapefile and extract it to your qgis_data directory, to a subdirectory named ms:

https://geospatialpython.googlecode.com/svn/mississippi.zip

In addition to the shapefile, you will also need the MapComposer class. This class encapsulates the boilerplate composer code in a reusable way to make adding other elements easier. You can download it from https://geospatialpython.googlecode.com/svn/MapComposer.py.

This file must be accessible from the QGIS Python console; ensure that it is in the Python path directory. Place...