The shape of the Personal World Map can be viewed according to three different kind of spaces: geographical space, travel time space and money space. These spaces are being modeled by distances: geographical distances, travel time distances and travel costs distances.
The geographical space is represented using the Azimuthal Equidistant Projection. This kind of projection has the advantage of showing distances from the center of the map to any other point in real magnitude. This projection is also the base for representing the travel time and money spaces; in these spaces geographical distances are replaced by travel time and travel costs distances, generating the distortion of the maps. This technique is known as anamorphosis. Maps produced in this way are called linear or distance cartograms or anamorphic maps.
It's important to note that travel time distance is the interval of time which separate the destination city from the departure city. When considering travel time it is not important which has been the route of the airplane or if the flight had one or more stops. Therefore, travel time is considered in the map as a straight line between the departure city and the destination.