QGIS Analysis – Network Service Area Analysis in QGIS

accessibilityanalysisbufferNetworkqgis

I want to check if schools from my hometown are accessible for students who use public transportation, so I need to perform this analysis in order to see if the schools are located in the range of ~400m, but I want to perform this as a network analysis using the roads, not just the buffer.

I have the following files: bus stations (points)- snapped to the lines, bus lines (vector line), and other roads and park alleys which I got from OSM (vector lines).

Is there a way I can perform this in QGIS? I tried various plugins but they are not working.

Best Answer

I'll show you two options for this (of course there are many more):

1. Use QGIS 3.x internal tool:

I suggest to reproject your data into a local metric (UTM) projection. Not sure if you get correct results when you use a non metric crs. (Just tested it in WGS84 and it works, but the results are sometimes different).

Then start the tool service area from layer. You can find it in your processing toolbox within networkanalysis. Choose your roadnetwork and your schools or busstops. Choose shortest and enter your distance in meters. Also take a look at advanced parameters to set up your service area more detailed.

If you want not just the lines when finished you can buffer the result.

2. Use OSM-Tools plugin and Openrouteservice

You can also use OSM-Tools plugin: https://plugins.qgis.org/plugins/OSMtools/ to calculate service areas (and more). It requires a registration on openrouteservice.org and a free API-Key. You can test the service here: https://maps.openrouteservice.org without registration.

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[GIS] How to draw a simple bus network that works with pgRouting

What you need for pgRouting - at minimum - is a table with edges:

edge_id, from_node, to_node, cost
1, 1, 2, 12.0
2, 2, 3, 57.0

Note that geometries of the edges are not necessary for most algorithms. Only the logical topology has to be created.

If you want to have edge geometries: start from the bus/train stop layer and create one edge for every connection (with snapping to the stops layer enabled). You can chose between assigning from_node and to_node ids manually or using one of the built-in pgRouting functions. For the automated process to work, you have to do a good job while digitizing the geometries.

Depending on how many bus/train lines you are planning to add, it might be advisable to try to automate as much of this process as possible. Is the "sort" attribute included in your bus stop data or did you have to add that manually?

Previous answer:

Since the ends of the two lines you show in the screenshot are very far apart, you would have to set the tolerance in pgr_createTopology really high (http://docs.pgrouting.org/dev/src/common/doc/functions/create_topology.html).

Instead you should pay more attention to digitizing the lines correctly by enabling snapping.

QGIS 3 – How to Create Vector Buffers in QGIS 3

I think you are currently using QGIS 3.0.0 or 3.0.1.

Latest QGIS 3.0.2 does not have Variable distance buffer anymore.

What you can find in the Vector | Geoprocessing Tools menu would simply be a Buffer.

It is the same in the Processing Toolbox... First. Fixed distance buffer disappeared, and now Variable distance buffer. There is only Buffer tool left.

Now with this Buffer tool, you will easily find Distance option. In case you need to apply a variable distance, click on the Data defined override icon and select the field you want to assign to.

Best Answer

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[GIS] How to draw a simple bus network that works with pgRouting

QGIS 3 – How to Create Vector Buffers in QGIS 3

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