[ISHMap-List] A critical review of the hypothesis of a medieval origin for portolan charts

Matthew Edney edney at usm.maine.edu
Sat Mar 15 14:04:21 CET 2014

Dear All:

It is always very difficult to respond to a press release, mostly because in my experience PR people routinely seek the "sexy" aspects that appeal to the lowest-common cultural denominator. (See the fourth of Luis's bullet points.)

The third of Luis's points exemplifies the problem: there, the reference to Mercator indicates a populist hook around which PR people can readily construct a narrative.

Overall, the press release suggests that the candidate undertook a numeric analysis of early portolan charts and concluded, in part, that such charts were based on some kind of projection similar to a Mercator projection. Yet  one can fit a set of functions to any map; does that mean the creator actually used those functions in creating the map (especially when portolan charts lacked indications of latitude and longitude!)? A numeric analysis of an early map cannot stand by itself and I very much hope that the full dissertation provides the necessary contextual information to support such a conclusion.


On Mar 15, 2014, at 3:36 AM, Luis Robles <luis.a.robles.macias at gmail.com> wrote:

> I received this news last Wednesday through from Frank Jacobs's "Strange Maps" blog in BigThink (http://bigthink.com/strange-maps/648-portolan-charts-too-accurate-to-be-medieval). I assume that many of you must have received it too but just in case I thought I should post it here for general information.
> Roel Nicolai, a PhD student at the University of Utrecht, presented last March 3 his doctoral dissertation entitled A critical review of the hypothesis of a medieval origin for portolan charts. He reached several provocative conclusions that I expect will stir debate among the members of the list. The book is not available online yet, but in the University's website there is a press release in English from which I have extracted the following statements:
> "A mathematical analysis of the oldest surviving portolan has revealed that its source data must have been derived from a portolan chart - instead of the other way round."
> "it is unlikely that the nautical compass was available in time and that  navigational methods used at that time were sophisticated enough to determine distances at such a degree of accuracy"
> "Nicolai has also established that portolan charts were drawn on the Mercator projection, or a similar type of projection."
> "they were much further advanced in terms of knowledge in the Middle Ages than we think"
> "An Arabic-Islamic origin is highly unlikely, according to Nicolai."
> "It therefore seems plausible that portolan charts originated from a tradition that is now lost. It is an intriguing question from what culture that tradition stemmed. Further research will be required to establish whether or not Greco-Roman antiquity is a realistic option, says Nicolai."
> The university does not say whether Mr Nicolai was awarded the doctorate or how to get access to his publication.
> -- 
> Luis A. Robles Macías
> Profile in Academia.edu
> Blog: http://historiaymapas.wordpress.com/
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Matthew Edney

Osher Professor in the History of Cartography (USM)

Director, History of Cartography Project (UW)

See http://www.maphistorydirectory.org/index.php/User:Edney.Matthew

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