Spatial distance analysis in QGIS

Question

I'm quite new to QGIS and trying to figure out how to analyze the following problem.

I have three layers:

1. settlements point layer with 253 entries
2. waste treatment facilities point layer with 24 entries
3. roads polyline layer

My problem is to find the distance between each settlement from layer (1) to each treatment facility in layer (2), however it has to be subjected to roads (layer 3), namely instead of getting aerial distance matrix I am looking for to the matrix that describes the actual driving distance.

I'm kindly asking your help with suggestion of how to perform this analysis with QGIS 1.7 (note that I don't know how to use PostGIS layers, if relevant)

• what plugin can or should I use?
• Should the polylines be connected to the points in both layers?

Answer 1

It has been a while and though there are answers about it somewhere in gis Q&A history, I've decided to use my question to share some of my findings regarding QGIS network analysis.

As @simplexio kindly suggested, postGIS with PgRouting is an option, though too complicated for me. I found out that with QGIS 1.8 the GRASS 6.4.2 plugin is quite sufficient to help with network analysis. It is easy to operate (since the plugin uses QGIS GUI, and some commands), the manual is easy to navigate and importing QGIS files or others is quite easy.

I hope to finish my work soon (overcoming some pc-related technical difficulties) and to upload my working process, since as a begginer it was the hardest for me to find a suffcient document or handbook to guide me through the process.