History of Longitude

Demo One Early Navigation- Pedro Reinel
and the beginnings of
understanding Longitude

Portuguese map-maker Pedro Reinel first drew the latitude lines
starting on the prime meridian in 1506.

By the 1520s, Portuguese cartographers realized that the scientific
precision necessary to fix latitude could only be approximated in
establishing longitude. Only a sufficiently accurate clock would finally
solve the problem. See John Harrison.

Beginning in the 1440s, Portuguese ships sailed
farther into the Atlantic and down the South
coast of Africa, first accumulating knowledge
of the South Atlantic in 1487, the Mozambique
channel in 1497, Brazil and Canada by 1502.
Thus they arrived in the New World.

The were a variety of ways to estimate the
difference in time between the starting point
(prime meridian) and where they were in
England, sailors began to use both Portuguese
and English standards. In 1884, a European
conference ratified a naval treaty placing of the
prime meridian in Greenwich England.

Zero longitude was first located in the
Portuguese Madeira Islands and for the next
300 years the world calculated longitude from
those Portuguese islands. Even as their
sea-power waned, Portugal's prime meridian
was the world's standard until the English
achieved became the dominate sea power in the
world and cracked the Longitude Problem.

Early Chart
by Pedro Reinel

This stamp marks the 500th
anniversary of the first map signed by
a Portuguese cartographer (a map of
Marear) by Pedro Reinel.

The Compass Rose
Pedro Reinel drew the first 32 point
compass rose with a fluer-de-lis indicating
north and the cross east- toward the Holy
Land. This began the tradition of drawing
the large compass rose on maps of West
Africa. This allowed pilots to plot courses on
either the North or South Atlantic Oceans.

Scholars think that Jorge Reinel,
the Portuguese cartographer, after
getting into trouble in Lisbon in
the early 1500s and fleeing to
Spain, made the first map of the
world. According to a report by
Lisbon’s ambassador to Seville in
1519 to the Portuguese king,
Reinel made a map specifically to
help Ferdinand Magellan prepare
for his voyage. Reinel’s father was
the prominent mapmaker Pedro
Reinel.

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