Università Cattolica del Sacro Cuore Università Cattolica del Sacro Cuore

Campus di Brescia

How Mercator Did it in 1569: From Tables of Rhumbs to a Cartographic Projection


Aula: Sala Riunioni -  Ore: 15.00

Via Musei 41, Brescia

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Università Cattolica del Sacro Cuore

Henrique LEITÃO
CIUHCT, Faculty of Science, University of Lisbon, Portugal

The celebrated cartographic projection first used by Gerard Mercator in his map of 1569 – Nova et aucta orbis terrae descriptio ad usum navigantium emendate accommodate [New and enlarged description of the world properly adapted for use in navigation] – is justly considered a landmark in the history of cartography. As is well known, in Mercator’s projection the spacing between adjacent parallels increases with latitude in such a way that angles are conserved, making the projection conformal. The consequence of extraordinary importance to marine navigation is that in this projection all rhumb lines (loxodromes) – the curved tracks of constant course followed by ships at sea – are represented by straight segments making true angles with the meridians. But how did Mercator originally conceive this idea? How was Mercator’s projection invented? Since Mercator himself left no record of the process that led him to this remarkable achievement, historians have debated the issue, for more than a century. The puzzle, however, appears to have been finally solved.

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