Global Positioning System Reference
In-Depth Information
the centuries, maps have helped guide ships, and ships have navigated to
unknown parts of the world in order to map them. Some of the tools and
methods of cartography are carried over directly into navigation. So, car-
tography is mapped in some of the chapters to follow. Remote sensing is
the essence of navigational data gathering. The term today applies to our
amazing electronic tools—radar and sonar, optical and infrared cameras,
magnetometers, and other measuring devices—that are used on, under, or
over both land and sea, and that look down upon the earth from space. It
also includes older and more familiar equipment such as telescopes, sex-
tants, and compasses. Navigation has provided the main motivation for
developing many of our remote sensing tools, and here I will look at these
tools and show you how they have changed the science of navigation.
Although most of the tangential details related to this huge subject have
been omitted, I could not resist including some of the more interesting
digressions, in boxes separated from the main text so as not to interrupt the
flow. So, where I feel that a biographical sketch is called for, or that a
navigational technique should be explained in more detail, you will find
these scattered throughout the text like islands in the ocean.
The prerequisites you need in order to appreciate this topic are (1) a
sense of wonder, (2) an interest in navigation and its history, and (3) high
school geometry. My geometrical approach is not lightweight, but it is
more digestible than algebra. You will be getting the whole meal deal here:
real explanations that distill the essence of a problem without belaboring
the math. In most of my topics I generally resort to mathematical analysis
because math is the only language that we scientists share with Mother
Nature. Here, however, the subject is so geometrical that I can get a lot of
the way there by substituting carefully drawn diagrams and asking you to
use your intelligence.
In a sense, navigation is a victim of its own success, in that nowadays we
barely need to think about it. If we are lost in a forest wilderness, we do not
fear goblins or even exposure; we just text our GPS coordinates to the
outside world. As a species, we have learned not to fear falling o√ the edge
of the world or entering unknown realms where there be dragons.
2
We
have explored and mapped the entire surface of our planet, above and
below the sea surface. We know the precise location of every city and
mountain on earth, and we have learned how to communicate rapidly with
2. Some old mapmakers labeled far-flung and unknown parts of the world with the
phrase ''here be dragons.''
