Keep line attributes in QGIS Network Analysis - Shortest Path

Question

I'm running a simply Shortest Path task from the Network Analysis toolbox in QGIS, but it seems that the output doesn't transfer the line attributes, only the start layer attributes. I need the road types and lengths so I can summarise how much of each are traversed.

I've already tried transferring the attributes by converting the lines to points and intersecting them and I've also simply tried intersecting the road network with the output lines, but the result is disconnected segments as it coincides in some parts and in other it just slightly doesn't overlap exactly (which should really be the case as I applied no snapping tolerances to the Shortest Route).

Anyway, this should be simple, but I don't see an option to retain the network attributes.

Answer 1

Well, there are some minor inaccuracies with the resulted route. There are multiple ways to achieve this which heavily depends on the size of your data.

Here is a rather lengthy, but fast in terms of performance:

1. First, buffer the roads by 2 meters. This value depends on the level of inaccuracy of route results.

2. Then select by location: select lines from your network that intersect with your buffer

3. After that explode the selected lines and get their centroids. Exploding them splits them into straight lines which positions the centroids on the lines.

4. Next step is buffering the points by the same amount of inaccuracy (2 meters) now you have polygons with the street information.

5. Explode the routes from the network analysis.

6. Finally spatial join the buffers with routes.

This should add attributes to the routes. you can dissolve the results based on the ID or name of the roads to have fewer shapes.

I recommend you to create a model in model builder for such lengthy processes.