I am struggling to find a path between health facilities in Madagascar.

I think that because the road network (from OpenStreetMap) is limited, the functions in QGIS, such as v.net.distance and shortest path (point to point) can't find a path.

The OSM tools plugin can't find a path either.

When I use the online routing mapper plugin, however, a path is always found.

Unfortunately, you can't import a shapefile, but you have to click on the coordinates to find a route. Since I have multiple health sites between which I would like to get a path, this is barely doable. My programming skills are very limited.

Is there a way to do it more efficiently or another plugin I should try or am I may be wrong to think the problem is due to a limited network?

  • Which QGIS version do you deploy? Have you researched other threads, e.g. Shortest path tool failed in QGIS, Finding the shortest path with online services in QGIS, 7.3. Lesson: Network Analysis - QGIS Documentation etc. The keypoint might be Network Analysis in QGIS. – Taras Mar 14 '19 at 10:27
  • I am using QGIS 3.2.1 Bonn and about the other threads: two of them are about the Roadgraph plugin, but I can't seem to find the plugin anymore. – Dana Mar 14 '19 at 10:33
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    Hi, i would suggest you to have a look at postgres SQL , you can use it with Qgis. And in postgres you have a nice extension called pgrouting. pgrouting.org – Maximilien jaffrès Mar 14 '19 at 10:58
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    To find a path, the (single part) linestrings of the network must be splitted at each intersection, also maybe snapped. That is, lines must be topological arcs and share a topological node. GRASS tool v.clean can do the job (break and snap methods). Points and lines must be defined in the same reference system as well. Are you sure that the requirements are met? I'm not sure but I think version 3.2.1 did not have a problem with those tools, but it would be good if you try an updated version. – Gabriel De Luca Mar 14 '19 at 11:01
  • Thank you for your help! Unfortunately, PostgresSQL seems to be quite complicated for me despite the user interface pgadmin.The v.clean function was very useful, as my network seemed to have many errors, but it still does not return a route between the points – Dana Mar 16 '19 at 14:44

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