The Two Point Equidistant projection is used to show the distance from "either of two chosen points to any other point on a map" (Environmental Systems Research Institute, 1997). Note that the first point has to be west of the second point. This projection has been used by the National Geographic Society to map areas of Asia.
Two Point Equidistant projection "does not represent great circle paths" (Environmental Systems Research Institute, 1997).
There is little distortion if two chosen points are within 45 degrees of each other.
This projection contains these unique parameters:
Longitude of 1st point
Latitude of 1st point
Longitude of 2nd point
Latitude of 2nd point
Two Point Equidistant Projection
Source: Snyder and Voxland, 1989