Lesson 4: Exploring
Where do We go from here?
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 from photographs). Photogrammetry is built on developments in many fields of science and technology. Leonardo 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 magnification. 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, 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 may mislead.
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.
Additional Activities
Visit a local government agency or private mapping organization for a demonstration of its mapping operation. If possible, visit a GIS (geographic information system) facility.
Invite an optometrist to class to discuss the physics behind the instruments used in a typical vision test.
Select two quotations from the Exlorers Section that seem especially pertinent to this activity sheet, and write an essay that discusses the ideas of both writers.
Recommended Reading
Hall, S.S. Mapping the Next Millennium‹The Discovery of New Geographies. New York: Random House, 1992.
Strain, Priscilla, and Engle, Frederick. Looking at Earth. Atlanta: Turner Publishing, Inc., 1992.
Geographic Information Systems. U.S. Geological Survey poster. 1992.
Planetary Maps. U.S. Geological Survey poster. 1992.
Topographic Mapping. U.S. Geological Survey booklet. 1991.
