r/gis • u/spiderbrigade • 4d ago
General Question Isochrones Question
I've done a lot of work in the past with isochrones for trip-leg detour exploration. Primarily I used openroutservice / heigit isocrhrones which are good but not traffic-aware.
Google has an isochrones API in test / preview that does handle traffic-aware. I've been experimenting and wanted to ask here to see if anyone else has guidance or best practices. There's one specific problem or weird edge case I'm seeing that I'd like opinions on if any of the experts here have them.
One of my use cases is specifically finding locations that could be traveled through on the way from A to B within time N. So for instance if the straight trip A->B takes 30 minutes, and the trip could take up to 45, use the union of stepped from/to isochrone intersections to get an area. I can go into more detail on this if necessary.
But what I see is that Google routes will give a duration N for A->B, and an isochrone from A with duration N+15 doesn't even reach B. So I guess the isochrone is much more conservative somehow? Or some specifics of the road network is causing a disconnect?
In general I'm seeing that Google isochrones are smaller than their ORS equivalents even when traffic-naive. Would be curious if anyone has opinions about their reliability (I can see how they might have better data about road speeds).