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Revisiting the Mercator World Map of 1569: an Assessment of Navigational Accuracy

Published online by Cambridge University Press:  13 June 2016

Joaquim Alves Gaspar
Joaquim Alves Gaspar*
Affiliation:
(Centro Interuniversitário de História das Ciências e da Tecnologia, University of Lisbon, Portugal)
*
(E-mail: [email protected])
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Abstract

An assessment of the navigational accuracy of the Mercator world map of 1569 is made, aimed at better understanding how the information was adapted from the contemporary cartography. At the time the map was engraved, navigational charts were constructed on the basis of astronomically-observed latitudes, magnetic courses and estimated distances between places. Before this information could be incorporated into the new world map it should be first transformed in such a way that the longitudinal spacings between places were restored to their correct values, as defined on the surface of the Earth. The question of whether Mercator performed such transformations or just considered that the positions were approximately correct has hitherto never been addressed in the literature. It is demonstrated in this article that Mercator was not fully aware of the complexity of the contemporary charts – which he considered to implicitly comprise a square grid of meridians and parallels – and that all planimetric information was directly imported to the novel world map without correction. It is further shown that the Mercator projection was not compatible with the navigational methods of the time.

Keywords

Mercator projectionHistory of CartographyMercator world map of 1569Cartometric analysis
Type
Research Article
Information
The Journal of Navigation , Volume 69 , Issue 6 , November 2016 , pp. 1183 - 1196
Copyright
Copyright © The Royal Institute of Navigation 2016 

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References

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