Or another way to look at it: if you model the earth as a perfect sphere, there&#x27;s a one-to-one monotonic relationship between geodesic distance and distance in a straight line <i>through</i> the earth. Points that are equidistant by one metric are also equidistant by the other.<p>So you could get exactly the same diagram by finding the 3D Voronoi diagram of the airports as a collection of points in space, and then taking the intersection of that with the geoid.