GIS Files 3: Adding real-world information

3.5: Structured GIS data is the key (3)

Road network data

One of the major uses of GIS is in the modelling of transport networks.

To get a really comprehensive model of a road network we have to look to large-scale sources for the most accurate possible information. However, the data attributes that are captured in the source mapping are the physical objects such as the roadside kerbs and the fences bordering the pavement. You can see that it is a road but there is nothing necessarily in the data to define discrete chunks of the road network.

This is why many mapping agencies have captured road centrelines in addition to the physical features shown on paper plans, as shown in the graphic on the right.

Ordnance Survey has generated a set of road centrelines showing the complete road network from the accurate information in the large-scale data – the resulting product is the OS MasterMap Integrated Transport Network Layer. Again, in isolation this data does not appear helpful in a visual sense. However, with its link and node topology (see chapter 2) and attributes about road names and numbers, ITN is the basis of many powerful GIS applications.

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