# What are the definitions of distance and area under Isochrones?

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.

Thanks.

Jin

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.

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?

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.