Roger Bacon's Terrestrial Coordinate System

Abstract

The paper introduces Roger Bacon's description of a system of plotting places with latitude and longitude in his thirteenth-century Opus Maius and raises questions about the nature and importance of the procedure he describes. It discounts previous claims that the procedure represented a fully developed map projection, but supports the case that Bacon had some understanding of the problems of representing a spherical earth on a flat plane. Bacon's system was innovative because he understood that the idea of coordinate systems could be transferred from a celestial to a terrestrial context, and that this idea had practical political—as well as spiritual—significance. But his ideas were not accepted until long after Ptolemy's Geography, which espoused a similar paradigm, reached Europe. Finally, Bacon's system seems innovative in the context of terrestrial cartography since it appears to assign equal geometric significance to each point in his “mapping-space.'’This departed from the route-enhancing space of the portolan charts and the center-enhancing space of the mappaemundi; it was a system that eventually was universally adopted for world mapping.

Key Words:

• Roger Bacon
• coordinate systems
• map transformations
• medieval world maps
• history of cartography