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San Martín's accurate longitude measurements on Magellan's circumnavigation: luck or mastery?

Published online by Cambridge University Press:  22 October 2024

Romeu Gaspar Open the ORCID record for Romeu Gaspar [Opens in a new window]
Romeu Gaspar*
Affiliation:
X&Y Partners, Lisbon, Portugal
*
*Corresponding author. E-mail: romeu.gaspar@thisisxy.com
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Abstract

During the 1519–1522 Magellan expedition, the astronomer Andrés de San Martín made two remarkably accurate longitude measurements, an order of magnitude better than what was typical for the 16th century. How he managed to do so remained shrouded in mystery for the past 500 years. Using modern ephemerides, we have retraced San Martín's observations and calculated their error signatures, clarifying the method he used (a simplified version of lunar distances) and why two out of his six measurements were accurate (a rather fortuitous cancellation of errors). It would be rash to dismiss San Martín's work as sheer luck though, as he was an exceedingly rare combination of a capable astronomer and a knowledgeable mariner.

Keywords

historyephemeris error estimationnavigationcartographymodelling

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Type
Research Article
Information
The Journal of Navigation , Volume 77 , Issue 1 , January 2024 , pp. 124 - 150
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Copyright
Copyright © The Author(s), 2024. Published by Cambridge University Press on behalf of The Royal Institute of Navigation

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