Hello,
I have a problem with the option avoid polygons.
I have a dataset with a lot of polygons (~100.000). This polygons I’d like to choose as “avoid Polygons”. So if I choose just a small number of this specific polygons the code is working. But if I choose all of them the code is not working.
Does anyone know the cause or/and a solution for this problem?
I use the ORS as a plugin in QGIS.
Best regards
Jonas
Hey,
100.000 is a huge number of polygons - I’m guessing that they do not comply with our API restrictions - for avoid polygons, there is a limit of a 200km² area (in total), and a limit of a 20 km extent (height or width).
Best regards
Thank you.
Do you know how the algorithm of the “avoid polygons” is working?
Would I get the same result if I just use the GIS-tool “Difference” to cut the “avoid polygone” from the isochrones?
Hey,
what happens in isochrones is that from your starting point, the algorithm starts to “explore” the road network in every direction, accumulating time or distance along each path taken.
Once the given limit is reached, it stops exploring and notes the points discovered (the “reachable” points).
From these points, the isochrone polygon is calculated.
When passing avoid polygons, roads in the polygons will not be used during the exploration. This might only have the effect that you described, essentially cutting the avoid polygon from the isochrone.
If you however imagine a single bridge over a river, if that bridge is in the avoid polygon, the other side of the river couldn’t be reached, and thus your isochrone would cut off at the river.
If you only cut your avoid polygon from your isochrone, that would look very differently.
So given the topology of your area and the nature of your avoid polygons, cutting them from the isochrones might be a decent approximation or could not be further from the truth…
Best regards
All right.
Thank you.