Exploration & Mapping
The changes in map data collection and display
that have occurred in the 20th century are comparable to the change from
pedestrian to astronaut. Information that used to be collected little by
little from ground observations, can now be collected instantly by satellites
hurtling through space, and recorded data can be flashed back to Earth at
the speed of light. Remote sensing devices collect data from parts of the
electromagnetic spectrum outside the narrow band of visible light. Gathering
gravity, magnetic, and other data takes us beyond the electromagnetic spectrum,
beyond our five senses into new territories, all of which can be mapped.
Fundamental to remote sensing is the practice of photogrammetry (measuring
Photogrammetry is built on developments in many fields of science and technology.
da Vinci (1452-1519), was perhaps the first to write about the theories
of optics. Italian and German painters and scientists explored the laws
of perspective in the early 1500's; these were enlarged upon in a 1759 treatise
by Henry Lambert, a French mathematician, who established the geometric
foundation of photogrammetry.
Stereoscopes that allowed two photographs to be viewed simultaneously to
create a three-dimensional view were first demonstrated in 1851, creating
a source of amusement and education.
When photography went airborne, first from balloons and later from airplanes,
stereoscopic cameras were used to make topographic maps.
Developments in remote sensing are founded on centuries of scientific work.
In 1514, Nicholas Copernicus, a Polish priest, suggested (anonymously at
first) that the Sun was the center of the solar system, an act of heresy
at the time, although it explained the observed motions of the planets.
Galileo Galilei's 1609 telescope demonstrated the importance of lenses for
In 1687, Isaac Newton's Principia Mathematica was published, establishing
the basic laws of motion and gravitation; Newton and‹and simultaneously
Gottfried Wilhelm von Leibnitz, in Germany‹developed the calculus, which
helped explain the mathematical principles behind elliptical orbits.
Engineering and computational advancements during the industrial revolution
and the spread of computers have taken mappers from ships to spaceships.
Developments in aeronautics and rocketry in the early 1900's, and in lasers,
computers, and satellites in recent decades, have given cartographers powerful
new tools. The 1936 Oswald Dome mosaic of aerial photographs and the 1937
topographic quadrangle of the same area were part of a test of the use of
stereoscopic aerial photographs in topographic mapping. Such photogrammetric
methods were incorporated into routine topographic map production in the
United States before World War II.
Since the late 1960's, map information has been collected, stored, and used
in digital form.
Satellites carrying remote sensing devices collect long strings of numeric
data and transmit the data to receivers on Earth.
The data are then reconstructed into digital images that look like photographs.
Cartographers now can gather spatial data and make maps faster than ever
before‹within hours and the accuracy of these maps is excellent. Moreover,
digital mapping enables mapmakers to experiment with a map's basic characteristics
(for example, scale or projection), to combine and manipulate map data,
to transmit entire maps electronically, and to produce unique maps on demand.
Geographic information systems (GIS) are computer systems
that store, manipulate, and display geographic information in layers, sets
of data that can be combined with other layers or manipulated and analyzed
individually. Results can be seen instantly on a computer screen, in some
cases replacing the need for paper maps, freeing the cartographer to experiment
with changes in the base map or in the spatial data. In addition to the
information content, the map scale, symbols (points, areas, and line styles),
colors, type, and overall layout can be changed quickly, greatly speeding
the process of mapping.
For all the benefits this technology offers, however, there is greater danger
of cartographic abuse now that powerful mapping tools are in inexperienced
hands. Different kinds of data are not always collected at the same scales;
data analysis is only as objective as the analyst; display techniques control
the information emphasized on a map. Now, more than ever before, some maps
Positional accuracy of information is being further refined by the Global
Positioning System (GPS), the basis of which is a set of satellites that
orbit about 12,000 miles above the Earth. Portable GPS receivers on Earth
receive the signals from GPS satellites above the horizon and calculate
absolute position to accuracies far better than those on existing maps of
most of the globe. The process is basic triangulation, but the new tools
provide much greater precision.
Mapping technologies are being used in many new applications. Biological
researchers are exploring the molecular structure of DNA ("mapping the genome"),
geophysicists are mapping the structure of the Earth's core, and oceanographers
are mapping the ocean floor. Computer games have various imaginary ''lands"
or levels where rules, hazards, and rewards change. Computerization now
challenges reality with "virtual reality," artificial environments that
simulate special situations, which may be useful in training and entertainment.
Mapping techniques are being used also in the realm of ideas. For example,
relationships between ideas can be shown using what are called concept maps.
Starting from a general or "central" idea, related ideas can be connected,
building a web around the main concept. This is not a map by any traditional
definition, but the tools and techniques of cartography are employed to
produce it, and in some ways it resembles a map. Indeed, our traditional
definition of a map is strained when we consider songs of aboriginal storytellers
as maps. This reinforces our recognition that maps are many things to many
people, and mapping transcends cultures and the ages.