Isochrones intersections for reachability analysis


#1

Hi everyone,

i’m new to gis, so please excuse my noob question.

I’m trying to conduct a reachability analysis using the isochrones api. I need to compare two locations and calculate their catchment area and find out how many people live in the respective area. That in itself is no problem, but the areas overlap. What I’m looking for now is a way to compute the border from where it is closer to location A and from where it is closer to location B, so that i can find out the disjunct catchment areas and their populations.

I found the intersect property in the API, but that only returns the multipolygon of the overlap area. That doesn’t do the trick, unfortunately. Is there an easy way to do this with the ORS api? If not, is there a client lib that i could use?

Thank you, any hints are appreciated!


#2

Hi @NeoTheThird,

we don’t provide this functionality, sorry. The intersection parameter should additionally return the polygons which interesect, however this is currently a little buggy. Depending on your language of choice, you could either use

Or simply install QGIS, it has all functions you need, https://qgis.org/en/site/ .


#3

Thanks for those links, @timothy. Qgis works for this more or less, but maybe it could be an idea to add this to the isochrones api in the future. I don’t see how this could be done efficiently and precisely with the libs you linked, not without making lots of api requests before at least. But since i got the data i needed with qgis, there’s no pressure for me. Thanks and keep up the good work!


#4

What you’re trying to do is the very basic GIS function of geometric difference and is built-in in any GIS lib, like the ones @timothy linked to. That’s why we won’t consider adding it to the API, it’s ubiquitous and a one-liner, while it’s not easy to implement on the backend.

See e.g.
https://shapely.readthedocs.io/en/stable/manual.html#object.difference