- Start up QGIS 2. Load and display a linear network layer e.g. segments.
- Select Vector | Road Graph | Settings.
The Road graph plugin settings appear.
- In the Layer field, choose the linear network layer e.g. segments.
- Optional. In the Time unit field, choose the time units to report on e.g. minutes.
- Optional. In the Distance unit field, choose the distance units to report on e.g. meter.
- Optional. In the Topology tolerance field, type in a non-zero value, if there are gaps in your linear network. Leave it zero if your network is topologically clean.
- Click the Default settings tab.
- In the Direction field, I chose Two-way direction as my network is bi-direction.
- Click OK.
- In the Shortest path pane's Start field, click the "cross" button.
- Click a starting point of the analysis in the map.
- In the Shortest path pane's Stop field, click the "cross" button. Click the ending point in the map.
- In the Criterion field, choose Distance.
- Click Calculate.
The shortest path by distance is calculated and displayed in the map.
Monday, November 18, 2013
Simple shortest path analysis using QGIS Road Graph plug-in
There is a Road Graph plug-in that can be installed in QGIS, and used to perform directional and non-directional shortest path analysis. Using the plug-in is quite straight forward, provided the network data is available and topologically clean. The following is an example showing a non-directional shortest path calculation using a linear metro network layer from a SpatiaLite database but it could from any GIS format.