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

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
Click to enlarge.
Click to enlarge.
This stamp marks the 500th anniversary of
the first map signed by a Portuguese
cartographer (a map of Marear)  by Pedro
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
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.
Watch Video on Early Navigation
Produced by the History Channel
Watch Video Lecture on the Discovery
of Longitude by Dr. Callahan
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