GIS Files 2: Geographical data

2.7: Topology (2)

The two most important aspects of topology in GIS are link-node topology and polygon topology.

Link-node topology

A GIS does more than just show the positions of objects on a computer screen – it can also be used to model real-world events. One of the most important examples of this is the ability to model networks. There are many networks in geographical data, such as water courses and street maps. A GIS can analyse the potential flow around these networks, a useful ability in flood analysis or route finding. It can only do this if the data has correct network topology – the joining of the lines at exactly the same point in the data. Lines in a GIS network are usually called links, the points which define the shape of the link are called vertices, and the points at which they join are called nodes.

We will learn later in chapter 4 how link-node topology can be used in network analysis.

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