Global Positioning System Reference
In-Depth Information
FIGURE 5.1.
A faint echo of
the Silk Road. This window
is in Paderborn Cathedral, in
Germany, and dates from
the Middle Ages. Yet the
theme of three hares—
common throughout
Western Europe at the
time—originated much
earlier and much further
east: it is Buddhist. The
three-hares motif spread
westward over the years
600-1500 CE along the Silk
Road.
Image from Wikimedia
Commons, User: Zefram,
CC by 2.5.
background and my bias toward navigating explorers. I certainly am not
suggesting a lesser achievement for those who are omitted here (Ericson,
Zheng He, Gonçalves, Cartier, Cortés, Frobisher, Pinto, Pizarro, Ricci, de
Champlain, Quirós, de Houtman, Tasman, Hudson, Bougainville, Macken-
zie, Park, Przhevalsky, Lewis and Clark,
1
Franklin, Leichhardt, Livingston,
Burton, Peary, Nansen, Amundsen, etc. etc. etc.). They all excelled, but
they are not part of our story.
Coastal Piloting
Seafarers since about 3500 BCE have set out to explore the wider world.
During the long dawn of navigation, they had very few of the tools that we
have seen—no mariner's compass or sextant, for example. They did have
sounding poles, or lead lines, to tell them about the depth of the waters
they sailed.
2
They built up knowledge of the winds and tides of the seas
1. Lewis and Clark performed many celestial measurements on their expedition, not to
determine a travel route but instead for the purposes of mapping the unknown (to Ameri-
cans) territory they were traversing. A telling indicator of this distinction—between naviga-
tional and cartographic observations—is that while Lewis and Clark made their observa-
tions, they did not always perform the calculations that would reduce their data to latitude
and longitude: they simply retained the data for analysis upon their return.
2. Lead weights attached to knotted ropes indicated the depth of coastal waters. Tallow
or wax coating on the lead weight would bring back up sediment from the seabed, which
