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CULHER-3274; No. of Pages 7 ARTICLE IN PRESS

Journal of Cultural Heritage xxx (2017) xxx–xxx

Available online at ScienceDirect www.sciencedirect.com

Original article

What is a , really? Uncovering the geometry of early modern nautical charts

a,∗ b

Joaquim Alves Gaspar , Henrique Leitão

a

Department of History and Philosophy of Sciences, Faculty of Sciences, University of Lisbon and Interuniversity Center for the History of Sciences and

Technology (CIUHCT), Campo Grande, Building C4, Room 4.3.11, 1749-016 Lisboa, Portugal

b

Department of History and Philosophy of Sciences, Faculty of Sciences, University of Lisbon and Interuniversity Center for the History of Sciences and

Technology (CIUHCT), Campo Grande, Building C4, Room 4.3.13, 1749-016 Lisboa, Portugal

a r t i c l e i n f o

a b s t r a c t

Article history: During the sixteenth century and beyond, nautical charts were the single most important source of

Received 9 May 2017

geographical information for the image of the world that was depicted in European maps and .

Accepted 11 September 2017

However, little was known until very recently about the geometry of these remarkable artefacts. Making

Available online xxx

use of results obtained with modern techniques of cartometric analysis and numerical modeling, we clar-

ify the nature of the early modern nautical chart and show how its geometry is intimately connected with

Keywords:

the contemporaneous navigational methods. Two major conclusions follow from our study: firstly, nau-

History of cartography

tical charts can only be understood in full cognizance of the navigational techniques they were intended

History of

to support; and secondly, nautical charts were instruments for navigation, not attempts at representing

Early modern maps

the Earth.

Early modern nautical charts

© 2017 Elsevier Masson SAS. All rights reserved.

Cartometric methods

1. Research aims 2. Introduction

This paper has been prepared in the scope of the European Few artifacts played such a crucial role in the process that led

Research Council project “The medieval and early modern nautical to the first geographical depiction of the whole world as the early

chart: birth, evolution and user (MEDEA-CHART)”, whose general modern nautical chart. From the second half of the fifteenth century

purpose is to solve a series of crucial questions pertaining to the onward, when the European maritime expansion began, nautical

birth, technical evolution and use of the medieval and early mod- charts largely exceeded their primary role as aids for navigation,

ern nautical charts. More specifically, the present research aims to become the single most important source of geographical infor-

at clarifying the following issues related to pre-Mercator nautical mation for the newly discovered lands. Printed depictions of the

cartography: world as famous as Martin Waldseemüller’s maps (1507, 1516),

the Mercator world map (1569) and Ortelius’s Theatrum Orbis

Terrarum (1570), all prepared by university-educated scholars, crit-

•

the inner geometric features of the charts, which reflect the

ically relied on the data imported from manuscript nautical charts,

navigational techniques used to acquire the geographical infor-

which had been collected by pilots at . Yet, despite their extraor-

mation;

dinary relevance in the construction of the first global depiction of

•

the purpose and use of the charts, as instruments for navigation;

the word, little is known about the true geometrical and instru-

•

the impact of nautical charts on the contemporaneous geograph-

mental nature of these amazing artefacts. Although the history

ical cartography.

of cartography is a well-established academic discipline and old

charts have been examined for many years, their detailed tech-

nical study is still in its infancy. The reason for this delay is that

historical research has mostly focused on the descriptive, political, ∗

Corresponding author.

artistic and symbolic components, while the most pressing of ques-

E-mail addresses: [email protected] (J. Alves Gaspar),

tions – what is a nautical chart, really? – has never been addressed [email protected] (H. Leitão).

http://dx.doi.org/10.1016/j.culher.2017.09.008

1296-2074/© 2017 Elsevier Masson SAS. All rights reserved.

Please cite this article in press as: J. Alves Gaspar, H. Leitão, What is a nautical chart, really? Uncovering the geometry of early modern

nautical charts, Journal of Cultural Heritage (2017), http://dx.doi.org/10.1016/j.culher.2017.09.008

G Model

CULHER-3274; No. of Pages 7 ARTICLE IN PRESS

2 J. Alves Gaspar, H. Leitão / Journal of Cultural Heritage xxx (2017) xxx–xxx

Fig. 1. Detail of a chart of the Caribbean Sea by Bartolomeu Velho (ca. 1560), showing the rhumb-line system, the Tropic of Cancer (horizontal red line), the scale of

(left border) and the distance bar (below the wind rose). Charts were used on the assumption that the north direction always pointed up, in the direction of the fleur-de-lis

of the wind roses, and that tracks followed by ships at sea were represented by straight segments. Huntington Library, San Marino, California (HM 44).

1

adequately. Instead, this question has been the object of a long nautical charts were constructed using the cylindrical equidistant

misunderstanding that developed from the sixteenth century on, projection [3,4]. The reason for the misinterpretation lies in the

and propagated to the present time. critical difference between what we call the external geometry of

In recent years, the development of new methods of cartomet- the charts, materialized by the scale, the distance bar and

ric analysis and numerical modeling has permitted to significantly the meshes of rhumb-lines that irradiate from certain spots on the

increase our understanding of specific geometric features of old charts (some decorated with wind roses) – intended to facilitate

nautical charts. We take the results of those studies, which are using them in navigation (Fig. 1) – and its internal geometry, asso-

excellent examples of how numerical techniques can contribute ciated with the representation of the actual geographic features

to solve questions that have resisted the traditional approaches of (coastlines, islands, etc.), which was frequently incoherent with

historical research, as the starting point for the present article. With the former. Charts were made and used on the assumption that

it, we propose to provide a complete and coherent explanation of all tracks followed by ships at sea, the rhumb-lines, were repre-

some issues pertaining to the geometry, the purpose and the impact sented as straight segments making with the north-south lines of

of pre-Mercator nautical charts. the wind rose systems the same angles as with the meridians on

the surface of the Earth. Moreover, all degrees were shown equal

on the scale of latitudes and a single distance scale (the scale of

3. The geometry of nautical charts

leagues or miles) applied to the whole area. Thus, in modern terms,

charts were made and used on the further assumption that the sur-

Contrarily to present-day maps and charts, which are pre-

face of the Earth could be locally represented by a tangent plane,

pared using the latitudes and longitudes of the places, and

where the curved angles and distances were approximated by the

adopt some appropriate , pre-Mercator nautical

corresponding plane quantities. An important consequence of this

charts were constructed on navigational information collected

assumption is that meridians and parallels were considered by the

by pilots at sea: courses, estimated distances and

pilots to be depicted as straight segments perpendicular to each

astronomically-observed latitudes. These elements of information

other. That is indeed the geometry implied in the mesh of rhumb-

where transferred directly to the plane of the chart, not considering

lines that is overlaid to all charts (the external geometry), where

that they had been measured on the spherical surface of the Earth.

the north-south lines are assumed to everywhere coincide with the

This was done not because of the ignorance of cartographers and

meridians, and the east-west ones with the parallels. When this fea-

pilots about the shape of our planet, but owing to the constraints

ture is combined with a linear scale of latitudes and a single distance

imposed by the navigational methods of the time. The procedure, 2

scale, a square grid of meridians and parallels naturally emerges.

although clearly documented in the contemporary sources, has

What pilots could not fully understand (although some may have

been largely ignored – when not directly refuted – by historians,

suspected) is that the procedure used to represent geographical

who almost consensually embraced the theory that early modern

1 2

In the authoritative multi-volume , several chapters are However, in a square grid of meridians and parallels (a cylindrical projection

devoted to nautical cartography [1,2]. In none of them is the geometry of early centered at the Equator, or plate carré) rhumb-lines are not generally depicted as

modern charts discussed, and only one is devoted to the mathematical aspects of straight segments, which makes such grid inconsistent with the mesh of straight

chart construction [3]. rhumb-lines shown on the charts.

Please cite this article in press as: J. Alves Gaspar, H. Leitão, What is a nautical chart, really? Uncovering the geometry of early modern

nautical charts, Journal of Cultural Heritage (2017), http://dx.doi.org/10.1016/j.culher.2017.09.008 Download English Version: https://daneshyari.com/en/article/7446181

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