Extracting town road networks from OpenStreetMap

A while ago I worked onĀ  a project that analysed the road networks in a number of towns and cities in England. Initially, we used the Ordnance Survey’s Integrated Transport Network (ITN). The process to extract an ITN network for a specific town was as follows:

  1. Using Digimap, extract the ITN network for a bounding box around the specific town.
  2. Extract the boundary polygon for the town and then trim the network to that polygon
  3. Tidy the road network – removing nodes (junctions) without edges (links), edges without a node at either end and disconnected islands. Fortunately, these tasks can be carried out within QGIS.

As you can imagine, this process is time-consuming and it limited the number of towns that we could analyse. Continue reading “Extracting town road networks from OpenStreetMap”

Network checking with QGIS

I’ve recently been doing some work with town and city road networks in the UK using the Ordnance Survey ITN network dataset. For each town I have been using its boundary, as defined in the UK Census, as a “cookie cutter” for the network. Unfortunately this can lead to an untidy network:

  • nodes without links (A below)
  • links without end nodes (B below)
  • disconnected “islands” (C below)

Continue reading “Network checking with QGIS”