Blending world map projections with Flex Projector

Abstract

The idea of designing a new map projection via combination of two projections is well established. Some of the most popular world map projections in use today were devised in this manner. One construction method is to combine two source projections along a common parallel; a second method calculates the arithmetic means of two projections. These two methods for creating new world map projections are included in the latest version of Flex Projector. Flex Projector, afreeware mapping application, offers a graphical approach for customizing existing projections and creating new projections. The Mixer is a new feature in the latest version that allows the user to blend two existing projections to create a new hybrid projection. In addition to the two established combination methods, the software includes a new method for blending projections specific to its visual design approach. With this new method, a unique trait of one projection is transferable to a second projection. Flex Projector allows for the blending of four different projection traits separately or in combination: (1) the horizontal length of parallels, (2) the vertical distance of parallels from the equator, (3) the distribution of meridians, and (4) the bending of parallels. This article briefly describes the main characteristics of Flex Projector and then documents the new approaches to projection blending. The integration of the three methods into Flex Projector makes creating new projections simple and easy to control and allows the user to evaluate distortion characteristics of new projections. As an applied example, the article also introduces the new Pacific projection that is a blend of the Ginzburg VIII and Mollweide projections.