we are map matching a bunch of routes (using GraphHopper 6.0), and we noticed that some routes cannot be map matched with contraction hierarchy. The map match of these routes doesn’t return an error, instead it returns a result with distance=0 and time=0.
The same routes are map-matched properly using Landmark.
Is this a limitation of map matching with contraction hierarchy? Shall we always use landmark with map matching?
Thanks for your help!
In principle there should be no reason not to use CH with map matching and the results should be the same. Can you describe exactly what you did so we can try to find the error (GH version, config file, possible code changes, map data and gpx track would be useful).
Whether or not CH (or LM) improve the map matching speed depends on the distance between the single tracking points. When it is small usually using neither LM nor CH is fastest.
Thanks. I’ll try to share all the needed info to reproduce it.
In the meanwhile, I saw that increasing the “max_visited_nodes” parameter from 1000 to 3000 fixes the map-matching with CH for those routes!
However, I’m not sure how to set the “max_visited_nodes” parameter to guarantee that all map-matching results are correct.
That’s interesting. CH should use less nodes than non-CH, but maybe the default limit is just higher without CH for some reason?