Global Positioning System Reference
In-Depth Information
Columbus as Navigator
Navigational tool were improving only gradually during the Age of Explora-
tion, as we have seen, and the practices of navigators during this period
reflect the mixture of old and new. Consider the crude manner in which Por-
tuguese ships navigated their
volta do mar
(return journey) to home port after
exploring the west coast of Africa. The winds and the Guinea Current obliged
them to adopt a broad sweep out to the open ocean on the way home, a route
known to them as the
Elmina track
. They found themselves heading north-
ward, out of sight of land, needing to turn eastward in order to reach Portugal.
Their navigational method was as simple as it was inefficient: they headed up
the Elmina track until the Pole Star was at the same altitude as it was at
Lisbon, and then they turned east. Given the long distance they still had to
travel, this was a rough-and-ready method at best because winds and ocean
currents could easily drag them off course. On the other hand, they knew
to compensate for the orbit of Polaris (by noting the orientation of the nearby
guard stars
), so at least that source of error was accounted for. Technically,
this mode of navigating is known as
altura
(height) sailing—a less precise
version of latitude navigation, which followed on from it.
A detailed analysis of his writings shows that Columbus, though a Geno-
ese in the employ of the Spanish court, was at heart a Portuguese navigator.
His training and experience, and his use of the tools of his trade, all point
to this conclusion. Columbus had an astrolabe and quadrant, with which he
measured the altitude of the sun and stars. He had crude charts, a lead line,
a sandglass, and possibly a sundial. Of these instruments, only the quad-
rant and astrolabe would have been unfamiliar to a mariner three centuries
earlier.*
One aspect of sailing that had not changed much since earlier times—and
would not for centuries after Columbus—was the superstition of sailors. This
characteristic of his crew (or perhaps their more pragmatic worries) caused
Columbus on his first outward voyage across the Atlantic to hide from them a
puzzling deflection of his compass away from the Pole Star and the true dis-
tance that his small flotilla had covered.
* Bedini (1998, pp. 512-14) provides details about Columbus's navigational training
and skills.
