Point of Departure - The Science of Navigation - page 2

maneuvering safely and e≈ciently from one part of the world to another.
Originally the word referred to ships, 1 including steering and the setting of
sails—all the skills needed to get a ship from home port to destination. This
topic is about our three-thousand-year-long journey from navigational in-
fancy (setting out from a harbor in a sailing craft, navigating by the Pole
Star and landmarks) to maturity (setting out from Times Square in a cab,
navigating by GPS). I describe not only the astounding feats of seamanship
and of determination in adverse circumstances of the early explorers, sail-
ors, and conquerors, but also the technical advances made by them, and by
many others behind the scenes, who developed the science of navigation.
My intent is to provide you with an understanding of the physical prin-
ciples that are needed to appreciate navigation and how they came to be
understood. I hope that you will close this topic with a deeper appreciation
of the physical, engineering, and mathematical ideas that have contributed
to developments in these fields and will see several layers beneath the
surface of modern navigational techniques. In these pages I survey a large
area—covering a lot of ground. Continuing the metaphor: the map I con-
struct is large scale, so it necessarily omits much detail. Thus, for example,
the fascinating, lengthy, and multifaceted story of the Great Trigonometric
Survey of India is here compressed into a few pages. Another example: the
well-documented and historically important survey of England is omitted
entirely. If you crave details, then please consult the extensive bibliogra-
phy. (Had I attempted a comprehensive coverage of all the disciplines
discussed in these pages, this topic would have required 10 volumes. More:
100 volumes. Under a single cover I can only explain the fundamental,
overarching ideas and hope to whet your appetite.)
The first chapters encompass preliminary material we will need later
on: geodesy and cartography. They set the table. These subjects, important
in their own right, are the appetizers before the main course of navigation
(apologies for the pun). I show you how navigation evolved and, along the
way, tell the stories of many historically important explorers who em-
ployed the navigational tools and techniques I discuss.
In chronological order our explorers are the unknown Phoenicians who
ventured into the southern hemisphere; two Carthaginians, Hanno and
Himilco, who expanded their trading contacts beyond the Mediterranean
and along the Atlantic coast; Pytheas, the Greek who ventured to the Arctic
Circle; Zhang Qian, the Chinese who explored the eastern lands of Alex-
1. The word navigate is derived from Latin navis , ''ship,'' and agere , ''to drive.''