[ISHMap-List] Cartographic innovations by the early portolan chartmakers

Wed Jan 4 09:53:20 CET 2017

Tony,

Thank you for making this work available online. Cartographic innovations on portolan charts constitute an interesting aspect of these charts. Your list establishes useful reference material. 

You invite comments and I am happy to oblige. Let me begin with the very first sentence. You state that “agreement is needed as to when those documents originated, before any cartographic innovations can be confidently attributed to portolan chartmakers”. This invites two comments.  Firstly “agreement” and “consensus” are desirable, but should not be the end goal of any researcher, who ought to aim primarily at delivering scientific or scholarly proof. Secondly, regarding the need to know the origin of portolan charts, the connection you propose between cartographic innovations and the charts’ origins is conjectural, not factual. Nevertheless, a good case may be made for a large number of innovations on the charts being medieval, but this is regardless of the question of the origin of the accurate coastal outlines.

In the last paragraph of the first chapter (“Introductory Notes”) you invite comments, but you exclude:
1.	speculation about portolan chart origins, and
2.	findings based on cartometric analysis
Excluding the first category is fully understandable and acceptable; the more so as your statement “The aim of this online Note is to bring together, in a summary form, scattered facts from portolan chart history” flies like a banner over the entire web page and note. It is therefore very odd that you exclude results from cartometric evidence. No method can ever deliver fully objective evidence – every method has its limitations and results are subject to interpretations, as I have tried to explain in Lisbon – but good cartometric evidence is as close as one can get to factual evidence about the charts. Excluding unwelcome facts is not a permissible action in anyone’s definition of the scientific method. You have professed not to understand the mathematics of my analysis, to me personally and in the September 2015 issue of Maps in History (page 27), accessible on http://www.bimcc.org/uploads/newsletters/nl53.pdf, but not understanding cartometric methods is no valid reason to exclude their results.

In the same paragraph you assert that “the following claims for innovations […] are unlikely to be challenged on factual grounds …”, a curious statement when one considers that you begin the new chapter not with an unchallengeable fact, but with the claim that “single largest innovation is undoubtedly an idea, the concept of a portolan chart”. The implication of this statement is that portolan charts would be original medieval creations. That is by no means a proven fact; it is, however, the premise of much research work on this subject, including, it appears, your own. You proceed to cite my own position, but I need to supplement this with some additional clarification. My position is not that they “have been passed down in their completed form”, that is, as complete charts of the Mediterranean, but that they were passed down as partial charts from an earlier period, which indeed has not been identified yet. I have proposed that these partial charts were copied and pasted together in medieval times to create a mosaic chart of the Mediterranean, the Black Sea and the Atlantic coasts. That alone would be a major cartographic innovation. Cartometric evidence is even available to suggest how that might have been done.

You claim that “if the […] cartographic novelties on Carte Pisane might be able to co-exist with that <Nicolai’s> argument, the major hydrographic improvements and the significant inventiveness […] during the few decades that followed evidently contradict it.” By using the word “evidently” you seem to suggest that the matter is so straightforward that no factual evidence needs to be presented. However, if the matter of the origin of portolan charts were so straightforward and self-evident, the debate on this subject, which has been going on for more than a century, would not have been there in the first place. Moreover, there is no factual connection between medieval cartographic innovations and the origin of the charts. You claim there is, but in the absence of clear proof, this is speculative. There is no conflict at all between those innovations and my conclusions, unless one insists that the accurate coastlines are an inalienable part of those innovations, which is exactly what I dispute.

In the next paragraph you express the hope that the “growing sophistication of cartometric methods may lead to a single understanding of the charts’ underlying geometry, around which an explanation of how they were constructed could coalesce both with the limited historical data available to us and the evidence drawn from the documents themselves”. This is a strange statement for someone who rejects such methods. My own cartometric analysis of five charts is arguably the most sophisticated one to date, but it led to conclusions that cannot find favour with you. My results also “coalesce with the evidence from the charts themselves” and with available historical evidence and better so than existing explanations, but the cited sentence suggests that you are calling for a cartometric analysis that will confirm your views on the origin and construction method of the charts! So, please explain what is incorrect in my cartometric analysis. If you do not understand how it works, how can you then reject my analysis or even suggest in a veiled manner that it is not sophisticated enough? Alternatively, if you believe my analysis to be correct but my conclusions to be wrong, we can start discussing how to interpret results such as: the division into subcharts, the overlaps and gaps between them, the scale and rotation angle differences and the analysis of the length of the portolan mile. This is highly relevant to the discussion on chart origins; you cannot therefore ignore this information.

In your list of innovations on the charts you do not mention two innovations in cartography which I consider to be the most significant ones, viz. the scale-truthfulness of the charts and the presence of the wind rose. Before the advent of portolan charts no known map was drawn to a consistent scale (neither was any map for a considerable period after that). Furthermore most medieval art distinguishes itself by its lack of a consistent scale, so scale-truthfulness is innovative in the Middle Ages. The wind rose itself was a major innovation, because it didn’t exist before (the naming system of winds probably did, but not the diagram). It allowed directional measurements to be made across the chart, a novel usage of a map. The innovation to the wind rose by Petrus Roselli you mention is actually a minor one, but you misunderstand its meaning. Roselli indeed drew 16 more lines through the centre point of the wind rose from about 1456 onwards, but this does not increase the number of distinct directions to 64, as you claim. This number remains 32, as the new lines do not constitute new directions; they were already present in the (old) wind rose but do not run through the centre.

I will limit myself to one more comment, one that has already been brought up by Luis Robles, viz. your claim of “a significant underestimation of its [the Mediterranean’s] length” on portolan charts.  Is this statement based on any factual information at all? As it happens the statement is completely false. The remarkable thing about the length of the Mediterranean on portolan charts is not its error, but the exactness of its value, as all cartometric analyses to date have demonstrated. When one rejects or mistrusts cartometric evidence and then makes a statement that is as factually incorrect as the one cited above, one really ought to reconsider the basis of one’s trust and mistrust in research methods.

A portolan chart is not a single coherent cartographic document, but a mosaic of partial charts. The length of the entire Mediterranean is therefore not a meaningful indicator of the accuracy of the charts. That subject has to be approached with more sophistication, through proper cartographic analysis. Then it will become evident that the western and the eastern Mediterranean on a portolan chart not only have their individual scales but also their individual anticlockwise rotation angles. Therefore any measures for quality cannot be taken across the extent of these two component charts unless their individual characteristics are taken into account.

Your list of cartographic innovations constitutes useful new information about the charts, but not all are beyond challenge. Regrettably your statements on the origin of portolan charts are no more than a regurgitation of the elements of the (near-)consensus hypothesis of a medieval origin, which is based on conjecture, but on no factual evidence. You characterised available origin hypotheses yourself as “creation myths” in your 1987 contribution to The History of Cartography Project. You have not added any facts about the origin of the charts, but only more conjecture, despite your resounding claims. In several places in your online Note you demonstrate that you either have not read my contribution to the question of the origin of the charts, or you have read it and have decided to ignore it completely. Either option is, frankly, unacceptable. It would benefit all researchers interested in this fascinating subject if you would come out in the open and discuss exactly what you think is wrong with my methods and my analysis results. Only after that discussion has taken place might we have a fruitful dialogue on whether those results indeed lead to my conclusions or whether alternative conclusions fit the facts better.

Roel Nicolai
University of Utrecht

-----Original Message-----
From: ishm-bounces at lazarus.elte.hu [mailto:ishm-bounces at lazarus.elte.hu] On Behalf Of Tony Campbell
Sent: Thursday, December 08, 2016 1:04 PM
To: ISHMap-List
Subject: [ISHMap-List] Cartographic innovations by the early portolan chartmakers

The following new online publication might be of interest to some on this list:

    *Cartographic innovations by the early portolan chartmakers*

*(and subsequent developments)***

*focusing through the centuries on the traditional medieval coverage:
*

*the Mediterranean and Black Seas, the North Sea and Baltic, and 
north-west Africa***

http://www.maphistory.info/PortolanChartInnovations.html

Abstract:

Since the medieval portolan charts were the earliest systematic and 
dedicated cartographic aids for marine navigation, it is inevitable that 
various hydrographic features will be appearing there for the first 
time.But, beyond that, the inventiveness of successive chartmakers led 
to the introduction of a number of conventions into cartography /as a 
whole/.Indeed, it is not unreasonable to claim that those charts, in the 
form they had achieved by the end of the developmental period (around 
1330), embodied more cartographic inventions than /any other map type/.

A list of the specific innovations found on the earliest survivors is 
followed by an itemising of the contrivances introduced on the work of 
Pietro Vesconte (1311-c.30) and those who came after him.

A number of the introductions, particularly the documenting of offshore 
hazards, were clearly designed as practical aids for mariners.Overall, 
what the charts offered seamen was unparalleled in its complexity and 
practical usefulness compared to anything made for landsmen.

The extended geographical coverage up to 1500 is described, along with 
the charts’ geometric and toponymic developments.A few were still being 
produced in the late 17^th century, which means that this visually 
distinctive genre of marine charts had a life of some 400 years.Such 
longevity, for a largely unchanging format retained for its practical 
utility, may well be unprecedented in cartography.

Comments are invited.

Tony Campbell

tony at tonycampbell.info
tonycampbellockendon at GMAIL.COM
info at maphistory.info

'Map History':http://www.maphistory.info
Academia:https://independent.academia.edu/CampbellTony
Twitter:https://twitter.com/portolanchart01

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