Roger Bacon's Terrestrial Coordinate System.

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. [ABSTRACT FROM AUTHOR]