navigation & cartography in the age of...

Navigation &

Cartography in the Age

of Discovery

26th January 2017

The Iberian Worldview c 1500

• Medieval society

• Spain & Portugal competing

to reach The Indies

Muslim block across the eastern Mediterranean

• Crusading zeal

• Search for Prester John

• Converts to the true faith

Challenges facing Explorers in Age of Discovery

What did they know of world?

What maps existed to guide thinking?

Who was going to pay for these adventures?

Did suitable vessels exist?

What experience of deep oceans?

Things we know

we don’t know

Things we don’t

know that

we don’t know

What we know

that we know

What we’re unaware

that we actually

do know

Extent of Africa

Location of Spice Islands

Eurasia

Existence of America,

Australia & Antartica

Mediterranean

Western Europe

North Africa

Earth is spherical

Size f the world

Cartography

Mappaemundi

Portolan Charts

Mediterranean-centric

Claudius Ptolemy, 1474

Martin Behaim’s Terrestrial Globe

Columbus’s compounding errors

Circumference of the earth

confused units between roman & arabic miles

30,200 kms instead of 40,000kms

Size of Eurasia

225o instead of 130o

Existence of islands off the coast of Cathay

inc mythical Antillia

Consequence:

estimated voyage from Canaries to Cipangu (Japan) as

4,000km, instead of 18,000

Dividing the World Between Spain & Portugal

• Two treaties (north - south)

• Tordesillas 1494 (east - west)

• Spanish sphere 370 leagues west of

Azores

• Portuguese everything to the east

• Granted sovereignty over land and sea of

undiscovered lands

• Sovereignity (imperium) not ownership

(dominium)

• Portuguese negotiated initial line westward

Portuguese geopolitical

heist?

Naval Architecture

Portuguese Caravel

approx 20m x 6m

Two masts

Latteen-rigged

shallow draft, manoeuvrable

max 300 tonnes

Capacity 20-30 crew

Spanish Carrack (Nao)

approx 30m x 6m

Single deck & three small masts

One aquare sail & two lanteen

shallow draft (3m)

100 - 300 tonnes

Capacity 40 crew

Experience of deep ocean sailing limited to the Atlantic

The First Circumnavigation Sept 1519 - Sept 1522

By MesserWoland and Petr Dlouhý CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)

Progress of Exploration

1434

1423

1492

1488

1498

1511

1542

1482

1521

1470

1500

Development of Portuguese Deep Ocean Navigation

Boxer 1969

World Map 1550