Straight and curved arrows with QGIS
After my previous posts on flow maps, many people asked me how to create the curved arrows that you see in these maps.
Arrow symbol layers were introduced in QGIS 2.16.
The following quick screencast shows how it is done. Note how additional nodes are added to make the curved arrows:
Free and Open Source GIS Ramblings 
Hello underdark, great screencast, very informative. It helps make an attractively shaped line to craft it for yourself.
I was actually just sitting down to create a map using your last solution, with a third point defined for each line. I’m preferring the database solution, since I can manipulate the data using SQL such that the normal two points in the line can be matched to something that matters, such as depart and arrive on a vehicle route, or origin-destination on some sort of flow.
Regards,
gxclark
This technique does not work for me when using shapefiles. When I make the node on the arrow and drag the node, straight lines appear between the new node and the end node. I saved the shapefile and a GeoPackage, put it on the map, and it curved the arrows without also creating the straight lines
Something else must have gone wrong there. It makes no difference if the data is stored in a Shapefile, GeoPackage or other format.