Introduction

This chapter focuses on the common use cases that are related to routing within networks. By far, the most common networks that are used to route are street networks. Other less common cases include networks for indoor routing, that is, through rooms inside buildings, or networks of shipping routes.

Networks and routing are in no way a GIS-only topic. You will find a lot of math literature related to this, called Graph Theory. In this chapter, we will use the following terms to talk about networks:

• A network (also known as graph) is a collection of connected objects
• These objects are called nodes (also known as vertices)
• The connections between nodes are called links (also known as edges)

The following figure explains these terms:

The two routing tools that are commonly used with QGIS are as follows:

• The Road graph plugin, which is one of the QGIS core plugins; that is, this plugin is available in every QGIS installation, but you may have to activate it in Plugin Manager
• The PostGIS...