What are the definitions of distance and area under Isochrones?

openrouteservice
#1

Hi,

Why are isochrone areas of the same range different in different cities? For Beijing, Beijing Shi, China, area is 51.35 km2 for range 5 km. For Olathe, Kansas, USA, area is 92.78 km2. What is the definition of area here? Area of a circle with 5 km radius is 78.5 km2; how do you get 92.78 km2?

Below are two screen captures. I don’t know if they will be displayed.

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Thanks.

Jin

#2

It was actually a bug, see here:

Basically, previously it used the wrong projection for area computation, WGS84. Now it uses an equal-area projection (I think Mollweide).

It’s not live on all servers yet, but will be very soon.

#3

Thanks. I think you answered my second question, “how do you get 92.78 km2?”.

What is the definition of area here? An area covering accessible roads and their buffers at a certain distance?

#4

The area of the isochrone’s geometry obviously… What you see in the map. It’s more or less the area covering accessible roads from the centre point.