Global Positioning System Reference
In-Depth Information
The Great Unknown
It is hardly surprising that, before their Age of Exploration, the European
maritime nations clung to the land like a fretful kid with water wings who,
learning to swim, clings to the edge of a swimming pool. The terrors of the
deep were real (and sailor's superstitions, as well as imagined sea monsters,
would not have helped). Consider the photograph here: this is what a mariner
in the open ocean sees—if he is lucky and the weather is good. Horizon. Noth-
ing on the surface to indicate direction or distance. If a medieval navigator
looked at the horizon from his deck, he might see a distance of 9 km (5 nautical
miles). From a crow's nest, the horizon would be twice as far away, at 18 km,
so that, on a good day, he might just be able to see the crow's nest of another
ship at 36 km.
This distance is nothing amid the vastness of the ocean: it would be very
easy to get separated from your fleet and find yourself alone and lost. Sup-
pose you were seeking land that rose 1,000 m above sea level. This land
would be hidden from your view by the curvature of the earth if you were
more than 130 km away—and that distance is less than 1.2 \ of latitude or
longitude. Consequently, European navigators were reluctant to let go of the
shore until they were confident that they could reliably estimate (at least one
of) these coordinates.
The briny deep. The open ocean provides the navigator of a sailing ship with no
surface indication of bearing or of distance traveled. I am grateful to Waldemar J. Poerner
for this image.
 
 
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