Global Positioning System Reference
In-Depth Information
On the brink of expanding into the world, Europeans had little in the
way of equipment to take them there. Indeed, it was finding the right
equipment that enabled them to explore and expand. The only strong
indicator that something might be stirring in this part of the world, to my
mind, was the portolan charts (fig. 5.8). These charts, recall, represented
accumulated practical knowledge of the waters and shores of the European
world, with information about harbors, currents, and wind patterns, and
every bit of useful knowledge that could be accrued and recorded. The
directions indicated on these charts were only approximate because they
were obtained by use of compasses, but magnetic variation was not a
problem; the navigators who used these charts also used compasses, so the
common declination error canceled. Only over time would the drifting
geomagnetic field cause di√erences between the directions indicated on
portolan charts and the same direction displayed on a mariner's compass;
thus, the charts required occasional updating.
Why do I consider the portolan charts to be an indicator of things to
come? These charts suggested that Europeans were once again learning
how to learn; they were applying knowledge to improve things, to enable
them to do something (in this case, piloting and navigation) better than be-
fore. The habits of intelligent observation and applied learning had largely
been lost since the end of the classical Greek era, over a thousand years
FIGURE 5.7.
A mari-
ner's compass, cra-
dled in a gimbal to
reduce the effects of a
pitching and rolling
deck, shown here in a
drawing from 1570.
Image from Wikipedia.
