Maps
To ask how far back mapping goes is to ask who was the first person to draw a diagram in the dust with a stick. Any attempt to schematically depict a geographic area can be considered a map, whether the purpose is to give someone directions or to define a territory. The Babylonians made maps on clay tablets as early as 2300 b.c., and the Egyptians may have had maps by 1300 b.c. It is known that diverse cultures such as Inuits and Polynesians made crude maps. Greek maps were the first to take into account a round earth and to use longitude and latitude lines. The philosopher Anaximander of Miletus (c. 611-546 b.c.) observed the revolution of the stars around the North Star and proposed that celestial objects are spheres. The historian Hecataeus (c. 550-476 b.c.) applied Anaximander's idea to his map of the earth and wrote the first book on geography in 500 b.c. Later Herodotus (c. 485-425 b.c.) expanded on Hecataeus's work, as did mathematician and astronomer Eudoxus (408-353 b.c.), who added a celestial map.
The Romans were master surveyors and builders, skills manifested in their ability to produce maps and plans. The Roman general Marcus Agrippa (63-12 b.c.) compiled a map of the Roman world based on military roads, which was completed by his sister. It is thought to have been derived from Eratosthenes's (c. 276-194 b.c.) world map. Around a.d. 150, Ptolemy ( a.d. 90-168) created a world map and a set of regional maps in his eight-volume Geographica. Ptolemy lived in Alexandria and compiled his masterpiece from existing Greek maps and information brought to him by world travelers. The map was a conical projection, bowing to the notion of a round earth, and listed over 8,000 place names. Ptolemy was considered the last scientific cartographer for the next 13 centuries, meaning that no improvements were made to his map in that time. Even after the Europeans learned about the Americas, the two continents were simply added to Ptolemy's map.
Early map making by the Chinese roughly paralleled that of the Greeks. In 271 a.d. the Chinese minister P'ei Hsin designed a map of China that employed the grid system of latitude and longitude. By 801 a.d. the geographer Chia Tan drew a map 30 by 33 feet (9 by 10 m), which with its roads and the distance between towns, predated similar maps in the West.
With the advent of the compass, sailor's charts, called portolanos, began to emerge in the 1300s. Portolanos eventually had rhumb lines added to them, which crisscrossed the maps and were used as compass guidelines for mariners. The first major change to map making came in the mid-1500s when Flemish cartographer Gerhard Kramer (1512-1594), better known as Gerardus Mercator, developed a new map projection that made map reading easier. This map, which stretches the features from the round earth on to a flat grid, is usually the first world map used by school children. All meridians (lines of longitude) are straight and are at right angles to the parallels (lines of latitude). Although it seriously distorts the features near the poles, the Mercator made it easier to relate geographic locations to each other because navigators could plot direction with a straight line on it. Mercator was the first to refer to his map collection as an atlas. Although he was not the first to use the name America (after geographer Amerigo Vespucci) for the New World, Mercator's use of the name on his maps, which were very popular for a long time, fixed the name in the world mind. Several years after Mercator developed his map, Scottish mathematician John Napier (1550-1617) invented logarithms and used them to calculate the earth's features on Mercator's map distortions.
The next important development in map making took place near the turn of the nineteenth century in the form of specialized maps. French cartographer Philippe Buache (1700-1773) pioneered the use of contour lines to express elevation. Other isograms included Edmond Halley's (1656-1742) wind and pressure lines (isanemones and isobars) and Alexander von Humboldt's (1767-1835) lines of equal temperature (isotherms). A new equal-area projection provided the answer to Mercator's distortions. With this method, the shapes of the continents are still distorted, but their sizes are proportional and thus more accurately depict the area of land masses. Other projections include the conical and azimuthal.
In the tradition of the Romans, the United States embarked upon a surveying effort during the 1800s that coincided with its rapid westward expansions. The natural result of this was a massive mapping effort that continues today. The United States Geological Survey is aggressively producing detailed topographical maps for the entire country. A key element of this effort is photogrammetry, the compilation of maps through aerial photography. Stereo imaging is achieved by mounting two cameras side-by-side on the underside of an airplane, imitating human vision. When viewed through special lenses, the double images appear in three dimensions. Satellites have greatly increased the ability to survey and map the earth. Landsat satellites, or ERTS (Earth Resources Technology Satellites), photograph the earth in 115-mile (185 km) north-south strips. They are used for mineralogical and agricultural surveys, and for weather observation. A popular product of Landsat are the infrared photographs that reveal crop damage and effects of drought and erosion. Mapping is being taken to ever-increasing heights, so to speak, with the launching of unmanned planetary missions. Spacecraft such as the Mariner, Voyager, and Pioneer have delivered photographs of the other planets of the solar system and many of their moons. In some cases, complete surveys have been made of major portions of planets, such as Mercury, from which atlases have been produced.
Digital computers entered into mapping during the 1970s and are expected to be the dominant force by the year 2000. Digitized maps are increasingly taking the place of manually produced maps. The computer stores the map, and any information keyed to it such as population statistics. Computers also allow for easier updating because map information has become databased. Computers are also playing an ever-increasing role in how maps are used. Consumers can buy maps and trip-planning software for use on their home personal computer. These maps can have numerous layers of cartographic information, more than any print map could contain on one page.
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