I am playing with GraphHopper since a long time but not with isochrones until recently…
I was wondering if the performances were “normal” in this situation: on a machine with 128 GB RAM, I have imported all the planet and I wanted to generate an isochrone from the center of Brussels by car with one hour travel time. (corresponds to /isochrone?point=50.8430033,4.3703459&time_limit=3600&distance_limit=0&profile=car)
First try: IllegalArgumentException with “Too many nodes would be included in post processing…” ==> I increased this number and I got a response in ~140 seconds…
I tried with GH V5 and V8, response time is very close, no real difference: do I have a performance issue or it’s considered as “normal” response time for that kind of query?
The isochrone calculation includes a Dijkstra-like graph exploration as well as the calculation of the contour line. If you use the /spt endpoint instead the latter will be skipped and I would expect a shorter calculation time. Did you try this yet?
I didn’t know this endpoint and, indeed, the response seems to be muuuuch faster! ~1 second for the same input
My need with the /isochrone endpoint was to have a multipolygon to put on a map and to search for real estate listings in this area => but the response with /spt endpoint is a CSV with a lot of points: do you think it’s possible to re-create a multipolygon from this points collection?
Yes, of course this is possible, because this is more or less what the /isochrone endpoint does on top of /spt. Depending on how exactly you are searching for the real estate listings /spt might be the better option. It basically gives you a list of all roads within the isochrone polygon and you can add extra columns representing some attributes of these roads (encoded values).
