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Cartography

Cartography

BIBLIOGRAPHY

Cartography is the science and art of map making as distinguished from assembling the data to be mapped, such as by surveying, by compilation from various sources, or by census-taking. It ordinarily encompasses a number of specialized technical phases: the scale of the mapping, the method of projection, the symbolization of the data being mapped, the map design, and the preparation of the map for duplication.

The primary function of a map is to serve as a reduction of all or part of the earth’s surface for the purpose of recording, presenting, or analyzing the spatial positions and the interrelationships of phenomena occurring thereon. Cartography, therefore, is both a prime research technique and a medium of communication for all those social sciences in which the spatial distribution of phenomena play any part, such as geography, history, anthropology, and economics. Furthermore, much of the data used by social scientists is available only in map form.

Although the variety is almost infinite, maps are commonly grouped in two classes: (a) reference maps, such as topographic maps, charts, or the general maps in atlases, and (b) thematic maps, or those dealing with a selected class or classes of data arrayed on a special base of reference material.

History of cartography. The concepts of scale reduction, direction, and distance seem innate in man, and the earliest map that has survived is more than four thousand years old. By the second century a.d. cartography had reached a high state of development, being known especially through the treatise of Ptolemy. Thereafter, except for its navigational aspect, cartography languished until the sixteenth century, when it began to develop quite rapidly. By the end of the eighteenth century all modern classes of maps had been developed except for the thematic map, which originated with the growth of science and social consciousness in the first half of the nineteenth century. Cartography was profoundly changed by the rise of geography as a scholarly discipline, the extension of the basic survey, and the development of many new techniques, such as lithography, photoengraving, the use of color, and statistical methods. Today, in addition to its general use in the preparation of topographic maps and hydrographic charts, cartography is widely used in the social and physical sciences and is a discipline in its own right. It is regularly taught in institutions of higher learning throughout the world and is represented by national and international organizations, such as the Congress on Surveying and Mapping (U.S.) and the International Cartographic Association.

The principal kinds of maps. The variety of maps does not allow a strict classification; but in practice the uses made of maps and the methods involved in their preparation separate them into several general categories.

Reference maps contain, to the limit of their scale, the readily observable features of primary interest to man. These include the coasts, the drainage features, the terrain, administrative boundaries, settlements, transportation facilities, and occasionally such special information as land use or vegetation. When of large scale and prepared from survey or by photogrammetric methods, such maps are classed as topographic; when of small scale and prepared by compilation from larger scale maps, they are simply termed reference maps.

Topographic maps are generally prepared by large governmental agencies, either military or nonmilitary, and are usually made according to a precise plan with extreme regard for planimetric accuracy. In many countries, maps have the status of legal documents. The coverage available is usually indicated on an index map. In general, the more heavily populated areas of the world have been mapped topographically (Karo 1955).

Other reference maps are of several kinds. Of principal use to the scholar, and to the public at large, are the reference maps and the specialized atlases (Yonge 1962a; 1962b). They are compiled from various sources, including topographic maps, and in addition to those that are essentially topographic maps on a small scale, there are usually others showing individual distributions such as population, temperature, economic activities, and political status. In recent years, many atlases of national areas have appeared that contain a wealth of detail far surpassing the so-called world atlases (International Geographical Union 1960). Atlases usually contain gazetteers of named places and features, whereas topographic maps do not. There are literally hundreds of atlases (Yonge 1962a; 1962b).

Another type of reference map is the cadastral plan. It is usually of much larger scale than the topographic map and commonly shows property boundaries, owners’ names, buildings, and roadways.

Thematic maps, which may also be used for reference, treat only a special class (or classes) of data, and the variety of other material included is carefully selected and is usually made subordinate to the primary data. Thematic maps commonly appear separately, but there are also thematic atlases of countries or of the world, such as historical, economic, and climatic atlases.

The sources of maps and map information are legion. Most libraries contain a file of atlases, and many institutions maintain a separate map library, the largest in the United States being the Division of Maps of the Library of Congress with its approximately 2.5 million maps.

The principal elements of cartography. All maps must be made to scale, and there are various aspects of scale that complicate their use. In its simplest form map scale refers to the ratio between some dimension on the map and the corresponding dimension on the earth stated as a proportion such as 1:250,000 or 1/250,000, the first element or numerator referring to the map and the second or denominator to the earth. This ratio, termed the representative fraction (rf), ordinarily refers to some linear relation; the squaring of the denominator in order that the rf may apply to areas is usually not stated. A large fraction, e.g., 1:50,000, is termed a large scale. The rf applied to a globe map is constant throughout the map; when scale is stated for a flat map, however, area scale can be held constant over the map area, but linear scale cannot. The amount of departure varies greatly with the system of map projection (Robinson [1953] 1960, pp. 26−28, 53−58).

All flat maps are based on a systematic framework that results from a transformation, to scale, of the earth’s spherical surface to the plane of the map. On account of the nonapplicability of these two surfaces, variations of linear scale over the map are inevitable. This results in deformation of angles or sizes of areas, or both, and consequent distortion of the representation of various earth attributes, such as azimuths, dimensions, and shapes. An infinite number of systems of projection are possible, but relatively few are regularly employed. Among the more important classes of systems are equivalent (maintenance of correct sizes of all areas), conformal (maintenance of correct angles at each point), and azimuthal (maintenance of correct azimuths at one point). In general, the amount of the inevitable change of linear scale over a map varies inversely with the rf of the map. The methods of analysis of scale variation stem from the mathematical work of Tissot and have been applied to the description of specific map projections in various ways (ibid., pp. 59−94, 324−329). In addition to the geographical coordinate system of latitude and longitude, many large−scale maps carry also a superimposed rectangular coordinate grid (Mitchell & Simmons 1945) by which positions may be given by listing the x value first, followed by the y value.

Every map must contain a selection of basic reference data to show locational relations among the mapped information. These must be generalized to a degree consistent with the scale of the map. Only at the largest scales can true intricacies and planimetric relationships be represented. The generalization must involve a selection from among the elements of each category and a simplification of their representation; since this must be done at all scales in varying degree, a map reader must be alert when deriving information from maps.

The symbols used to convey the information to the reader consist of a variety of marks, commonly categorized as point, line, and area symbols. They may appear in one or more colors. Point symbols, such as dots, circles, and triangles, may portray qualitative aspects, such as the existence of a city, or, by variations of the size or number of the symbols, may also portray quantity. Line symbols range from the simple line representing a linear quality, such as a road, an air route, or a boundary, to a class having the generic name isarithm, which represents quantitative aspects that include a wide variety of variants with special names (Horn 1959). The isarithm is commonly used to portray distributions that vary in amount from place to place, such as elevation of the land surface above sea level (contour), but it may be employed for more abstract concepts (Robinson 1961). An isarithm is the line on a map that shows the orthogonal map position of the trace of an assumed horizontal plane with the surface of the actual or assumed three-dimensional distribution being mapped. The vertical spacing of the assumed planes (the interval), when combined with the map scale, provides information concerning the gradients of the distribution. This is shown directly by the spacing of the isarithms (Robinson [1953] 1960, pp. 178−194).

Gradients or actual flow may be represented by the “flow line,” another class of line symbol, the width of which varies in direct proportion to the magnitude (slope, volume, speed, etc.) that occurs at each point or selected point along the line. Lines may be varied in appearance (dots, dashes, colors, etc.) to identify the classes of data to which they refer. Area symbols are various patterns of marks or colors applied to regions to show either the quality, e.g., vegetation or political affiliation, or the quantity included within a region. The boundaries of the region so designated may be defined by the qualitative limit, by isarithms, by the boundaries of enumeration districts (choroplethic), or by some internal characteristic of the distribution, such as zones of rapid gradient (dasymetric). The employment of map symbols is very complex and the map maker and user must be alert to their many implications (ibid., pp. 136–154).

The final element of the map is the lettering applied to identify specific locations or the characteristics of the mapped data. There are three major aspects of cartographic lettering. The first involves the style and size of the lettering. Lettering was formerly done freehand or sometimes by an engraver, but today it is usually done with the aid of mechanical devices, by the incorporation of photographically composed words, or by the application of preprinted lettering from type (ibid., pp. 243–263). All sizes and styles may be used on maps, but because the lettering is to be read it must be large enough, and because the various styles may provide subjective reactions and either harmonize or conflict with the other map data, the choice of lettering is an exacting process. The spelling of the words to be used is subject to numerous complications: local use may differ from official use; the alphabets employed may be different, as in the transliteration of Chinese characters; convention may depart from reality, e.g., Danube River; and official use may change from time to time, as countries are created or administrations change. Because of the confusion that results from these conditions, the United States has established a Board on Geographic Names in the Department of the Interior charged with deciding official use. The board publishes numerous lists, recommendations, and policy statements. Moreover, the positioning of the lettering on maps has many ramifications and must be done with care (Imhof 1962).

The design of a map involves many of the considerations already mentioned. For purposes of scientific communication the map, as a functional tool, must be appropriately designed. If the proper line weights, lettering styles, projection, scale distribution, colors, and patterns are not employed, the map reader may easily be misled; and it is not uncommon for maps to be designed for propaganda purposes, without due regard for intellectual honesty and without adequate understanding of the effects of design (Robinson 1952). The map reader and map maker, as Wright (1942) has pointed out, must be ever alert against the possibility of subjective impressions at variance with reality.

The reproduction of the map is usually necessary and may be accomplished by many methods (Robinson [1953] 1960, pp. 264−282). Except for very simple maps, the actual drafting and preparation of copy for the printer have reached such complex technical proportions that they are beyond the capabilities of the noncartographer. The person without cartographic training should never attempt this phase without seeking advice.

Cartography is an indispensable research tool in numerous ways. Its prime function is to make possible the analysis of the elements of spatial variation inherent in the distributional qualities of the data under consideration, such as the relation of distance to cost or time of transport, the relation of urban development to functional areas, or the relation of productive capacity of the environment to population distribution or character. Before analyses of this kind can be properly carried on, the spatial aspects of such data must be mapped so that they are capable of correlation with other distributional data. Techniques for correlating with some precision several quantitative distributions are now available (Robinson 1962), as are methods for mapping residuals from spatial regression (Thomas 1960). The development of location theory and spatial structure may be aided theoretically by methods of modifying the natural horizontal scale relationships of distributions in order to remove unwanted influences (Tobler 1963), but as yet this very complex process is in its infancy. Cartography is also a standard medium of communication, providing the social scientist with a means of displaying the areal relationship involved in his analyses as well as his conclusions. Such maps are usually quite different from those used for research purposes and must be carefully designed not to give wrong impressions (Robinson 1952).

Research in cartography is advancing along many lines. Of indirect concern to the social scientist are the many investigations into the methods of preparing the large-scale reference maps from which come all the basic data for the other forms of cartography. These are carried on primarily in government institutions. Of direct concern are the avenues of research relating to the map as a research tool and to its employment as a medium of communication. Currently under investigation are methods of deriving the error factor in quantitative mapping; the design of graduated quantitative point symbols, e.g., circles, so that the communication of data will fit psychophysical standards; the employment of statistical methods in the spatial (cartographic) context; the role and practice of cartographic generalization ranging from such linear elements as coastlines, drainage, and boundaries to the analysis of isarithmic and choroplethic intervals; and the design and employment of colors, patterns, and tones as area symbols. An increasing amount of research is being devoted to historical cartography, much of which is concerned with the developments in the post-Renaissance period, but an increasing awareness of the magnitude of the current revolution in cartography has stimulated investigations into the post-1800 developments.

Arthur H. Robinson

[See alsoArea; Central place; Geography; Graphic presentation.]

BIBLIOGRAPHY

Eckert, Max 1921−1925 Die Kartenwissenschaft: Forschungen und Grundlagen zu einer Kartographie als Wissenschaft. 2 vols. Berlin and Leipzig: Gruyter.

Ekman, Gosta; Lindman, Ralf; and William-Olsson, William 1961 A Psychophysical Study of Cartographic Symbols. Perceptual and Motor Skills 13:355−368.

Horn, Werner 1959 Die Geschichte der Isarithmenkarten. Petermanns geographische Mitteilungen 103:225−232.

Imhof, Eduard 1961 Isolinienkarten. International Yearbook of Cartography 1:64−98.

Imhof, Eduard 1962 Die Anordnung der Namen in der Karte. International Yearbook of Cartography 2:93−129.

International Geographical Union, Commission des Atlas Nationaux 1960 Atlas nationaux: Histoire, analyse, voies de perfectionnement et d’unification. Moscow: Akademiia Nauk SSSR.

Jenks, George F.; and Knos, Duane S. 1961 The Use of Shaded Patterns in Graded Series. Association of American Geographers, Annals 51:316−334.

Karo, H. Arnold 1955 World Mapping. Washington: Industrial College of the Armed Forces.

Mitchell, Hugh C.; and Simmons, Lansing G. 1945 State Coordinate Systems (A Manual for Surveyors). U.S. Coast and Geodetic Survey, Special Publication No. 235. Washington: Government Printing Office.

Pannekoek, A. J. 1962 Generalization of Coastlines and Contours. International Yearbook of Cartography 2: 55−75.

Raisz, Erwin J. (1938) 1948 General Cartography. 2d ed. New York: McGraw-Hill.

Report of the Group of Experts on Geographical Names. 1962 World Cartography 7:7−18.

Robinson, Arthur H. 1952 The Look of Maps: An Examination of Cartographic Design. Madison: Univ. of Wisconsin Press.

Robinson, Arthur H. (1953) 1960 Elements of Cartography. 2d ed. New York: Wiley.

Robinson, Arthur H. 1961 The Cartographic Representation of the Statistical Surface. International Yearbook of Cartography 1: 53−63.

Robinson, Arthur H. 1962 Mapping the Correspondence of Isarithmic Maps. Association of American Geographers, Annals 52:414−429.

Thomas, Edwin N. 1960 Maps of Residuals From Regression: Their Characteristics and Uses in Geographic Research. Iowa City: State Univ. of Iowa, Department of Geography.

Tobler, Waldo R. 1963 Geographical Area and Map Projections. Geographical Review 53:59−78.

U.S. Department of the Army 1951 The Universal Grid Systems: Universal Transverse Mercator and Universal Polar Stereographic. TM 5−241/TO 16−1−233. Washington: Government Printing Office.

Wright, John K. 1942 Map Makers Are Human: Comments on the Subjective in Maps. Geographical Review 32:527−544.

Yale University, Map Laboratory 1956 Statistical Symbols for Maps: Their Design and Relative Values. New Haven: The University.

Yonge, Ena L. 1962a Regional Atlases: A Summary Survey. Geographical Review 52:407−432.

Yonge, Ena L. 1962b World and Thematic Atlases: A Summary Survey. Geographical Review 52:583−596.

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Cartography

CARTOGRAPHY

CARTOGRAPHY. The science of mapmaking in the United States has developed along two main lines, commercial and governmental, producing different kinds of maps for different purposes.

Commercial Mapping and Mapmaking

Commercial or nongovernmental mapping and mapmaking began immediately after the Revolution with proposals by William Tatham, Thomas Hutchins, Simeon De Witt, and other topographers and geographers who had served in the army to compile maps of the states and regions of the United States. Since then, the three most widely published types of commercial maps have been geographical national and world atlases, county atlases, and individual maps.

Geographical atlases and maps were first published in the United States in the early 1790s—for example, Matthew Carey's American Atlas, published in Philadelphia in 1795. By the 1820s the best work was being done by Henry C. Carey and Isaac Lea, Samuel E. Morse and Sidney Breese, Henry S. Tanner, and John Melish. Melish's Map of Pennsylvania (1822) and Herman Böyë's Map of the State of Virginia (1826) are excellent examples of large-scale state maps. The principal centers of publication during most of the nineteenth century were Philadelphia, Boston, New York, and Chicago.

Prior to the introduction of lithography in about 1830, maps were printed from copper engravings. Use of lithography expedited publication of maps in variant


forms and made them appreciably less expensive. These technical improvements rapidly increased commercial map publication. Meanwhile, the rapid expansion of white settlement into the West and the spread of American business interests abroad elicited a considerable interest in maps, either as individual state and county sheets or in atlases.

By midcentury, map publication was accelerated by the introduction of the rotary steam press, zinc plates, the transfer process, glazed paper, chromolithography, and the application of photography to printing. Two major map publishers, August Hoen of Baltimore and Julius Bien of New York, set the high standards of cartographic excellence during the second half of the nineteenth century. They produced many of the outstanding examples of cartographic presentation, especially those included in government publications. A. Hoen and Company was still making maps in the mid-1970s. Others who contributed significantly to the development of techniques of survey, compilation, and map reproduction were Robert Pearsall Smith and Henry Francis Walling. A uniquely American form of commercial map publication in the second half of the nineteenth century was the county atlas and, to some extent, the city and town map. In addition, the fire insurance and underwriters map was developed during this period. The Sanborn Map Company perfected these maps in great detail and, until the 1960s, kept them upto-date for most cities and towns of the United States.

During and after World War II commercial map production accelerated rapidly. Government mapping and mapmaking agencies contracted out to commercial map publishing firms large orders for many kinds of maps and atlases. Aerial and satellite photography, especially since World War II, has become a fundamental source of information in map compilation. Commercial map publication during the twentieth century expanded to include a wide variety of subjects, such as recreational, travel, road, airline, sports, oil and mineral exploration, and astronautical exploration maps, catering to a rapidly growing interest in graphic information. Using census and survey data, marketing firms have developed sophisticated maps to help them chart and predict consumer trends. In the late twentieth century, computer technology transformed the making and consumption of maps. Maps of high quality and detail, capable of being tailored to consumers' individual needs, became widely available in computer format. But computers and the Internet have also made it possible for noncartographers to produce and distribute maps of dubious accuracy.

Federal Mapping and Mapmaking

In a resolution of the Continental Congress on 25 July 1777, General George Washington was empowered to appoint Robert Erskine geographer and surveyor on Washington's headquarters staff. Under Erskine and his successors, Simeon De Witt and Thomas Hutchins, more than 130 manuscript maps were prepared. From these beginnings a considerable mapping program by the federal government has evolved that since the early days of World War II has literally covered the world, and since 1964, the moon.

In 1785 the Congress established a Land Ordinance to provide for the survey of public land, and in 1812 it created the General Land Office in the Department of the Treasury. The activity of this office has, in varying forms, continued to this day. Increase in maritime commerce brought about, in 1807, the creation of an office for the survey of the coasts, which, with several modifications and a lapse between 1819 and 1832, has continued through to the present as the U.S. Coast and Geodetic Survey. The rapid movement of population to the West and the large acquisition of lands by the Louisiana Purchase increased the need for exploration, survey, and mapping, much of which was accomplished by topographical engineer officers of the War Department.

Between 1818 and the eve of the Civil War, the map-ping activities of the federal government increased greatly. A topographical bureau established in the War Department in 1818 was responsible for a nationwide program of mapping for internal improvements and, through detailed topographic surveying, for maps and geographical reports. A cartographic office that was set up in the U.S. Navy Depot of Charts and Instruments in 1842 was instrumental in the mapping of the Arctic and Antarctic regions and the Pacific Ocean and in supplying the navy with charts. In the 1850s the Office of Explorations and Surveys was created in the Office of the Secretary of War, with a primary responsibility for explorations, surveys, and maps of the West—especially for proposed and projected railroad routes to the Pacific coast.

During the Civil War the best European surveying, mapmaking, and map reproduction techniques were blended with those of U.S. cartographic establishments—especially in the Union and Confederate armies. By the end of the war, which had revealed the inadequacy of map coverage for military as well as civilian enterprise, U.S. mapmaking was equal to any in Europe. A few of the mapping agencies created between the Civil War and World War I to serve the federal government's needs include the Bureau of the Census, which, beginning in 1874, published thematic demographic maps and atlases compiled principally from returns of the census; the Geological Survey, created in 1879 to prepare large-scale topographic and other maps, almost exclusively of the United States and its territories; the Hydrographic Office of the navy, established in 1866 to chart foreign waters; the Corps of Engineers, expanded greatly to undertake a major program of mapping and surveying for internal improvements; and the Weather Bureau, organized in 1870 in the Signal Office of the War Department to prepare daily, synoptic, and other kinds of weather maps.

World War I created a need for maps by the military, especially in Europe. Mapmaking and map reproduction units were organized and established in France. Some of the maps were made from aerial photographs and represented the beginning of modern quantitative mapping with a respectable degree of accuracy. New techniques of compilation and drafting and improved methods of rapid reproduction developed during the war accelerated and widened the opportunities for mapping during the 1920s and 1930s.

In part to provide work for unemployed cartographers and writers, during the Great Depression many specialized agencies were created to map a wide variety of cultural and physical features. Thematic and special-purpose maps—many of which were included with government reports—came into their own. Significant among the specialized agencies were the Bureau of Agricultural Economics, the Tennessee Valley Authority, the Climatic and Physiographic Division, the National Resources Committee and Planning Board, and the Federal Housing Administration. Geographers played a leading role in the development of techniques for presentation, especially in thematic and resource maps, and in field mapping.

Mapping agencies proliferated in the federal government during World War II. The principal types of maps of this period were topographic maps, aeronautical and nautical charts, and thematic maps. Several hundred geographers in Washington, D.C., alone were given responsibilities for mapmaking and geographical interpretation, particularly in the compilation of thematic maps. The wide use of aerial photography during the depression was expanded to universal application, especially for the making of large-scale topographic maps. The Aeronautical Chart and Information Service, the Hydrographic Office, and the Army Map Service, with their numerous field units, were the primary agencies of production.

The postwar period witnessed the spread of military and scientific mapping in all parts of the globe. The development of color-sensitive photographic instruments, of highly sophisticated cameras in space vehicles, of automated cartography combining electronics with computer technology, of sensing by satellites in prescribed earth orbits, and of a host of other kinds of instrumentation has made possible a wide variety of almost instantaneous mapping or terrain imaging of any part of the earth. By the 1980s and 1990s these sophisticated maps had assumed a central role in military reconnaissance and field operations. The U.S. military's reliance on maps was made all too clear during the 1999 NATO action in Yugoslavia, when an outdated map of Sarajevo resulted in the accidental bombing of the Chinese embassy there. As mapping has become an increasingly exact science, maps have become a fundamental source of information and a basic record in most agencies of the federal government.

BIBLIOGRAPHY

Brown, Lloyd A. The Story of Maps. Boston: Little, Brown, 1949.

Cumming, William P. British Maps of Colonial America. Chicago: University of Chicago Press, 1974.

McElfresh, Earl B. Maps and Mapmakers of the Civil War. New York: Abrams, 1999.

Ristow, Walter W. American Maps and Mapmakers: Commercial Cartography in the Nineteenth Century. Detroit, Mich.: Wayne State University Press, 1985.

Thompson, Morris M. Maps for America: Cartographic Products of the U.S. Geological Survey and Others. Reston, Va.: Department of Interior, Geological Survey, 1979.

U.S. National Archives. Guide to Cartographic Records in the National Archives. Washington, D.C.: U.S. Government Printing Office, 1971.

Wheat, James C. Maps and Charts Published in America before 1800: A Bibliography. 2d rev. ed. London: Holland Press, 1985.

Herman R.Friis/a. r.

See alsoCoast and Geodetic Survey ; Geography ; Geological Survey, U.S. ; Geophysical Explorations ; Maps and Mapmaking ; Printing Industry ; Surveying .

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Cartography

Cartography

Cartography is the creation, production, and study of maps. It is considered a subdiscipline of geography, the study of spatial distribution of various phenomena. Cartographers are often geographers who particularly enjoy the combination of art, science, and technology employed in the making and studying of maps.

A map is a generalized two-dimensional representation of the spatial distribution of one or more phenomena. For example, a map may show the location of cities, mountain ranges, and rivers , or may show the types of rock in a given region. Maps are flat, making their production, storage, and handling relatively easy. Maps present their information to the viewer at a reduced scale. They are smaller than the area they represent, using mathematical relationships to maintain proportionally accurate geographic relationships between various phenomena. Maps show the location of selected phenomena by using symbols that are identified in a legend.

There are many different types of maps. A common classification system divides maps into two categories, general and thematic. General maps are maps that show spatial relationships between a variety of geographic features and phenomena, emphasizing their location relative to one another. Thematic maps illustrate the spatial variations of a single phenomenon, or the spatial relationship between two particular phenomena, emphasizing the pattern of the distribution.

Many maps can be either general or thematic, depending on the intent of the cartographer. For example, a cartographer may produce a vegetation map, one that shows the distribution of various plant communities. If the cartographer shows the location of various plant communities in relation to a number of other geographic features, the map is properly considered a general map. The map is more likely to be considered thematic if the cartographer uses it to focus on something about the relationship of the plant communities to each other, or to another particular phenomenon or feature, such as the differences in plant communities associated with changes in elevation or changes in soil type.

Some examples of general maps include large-scale and medium-scale topographic maps, planometric maps, and charts. Topographic maps show all-important physical and cultural features, including relief . Relief is the difference in elevation of various parts of the earth's surface. Planometric maps are similar to topographic maps, but omit changes in elevation. Charts are used by the navigators of aircraft and seagoing vessels to establish bearings and plot positions and courses. World maps on a small- or medium-scale showing physical and cultural features, such as those in atlases, are also considered general maps.

Although the subject matter of thematic maps is nearly infinite, cartographers use common techniques involving points, lines, and aerial photos to illustrate the structure of spatial distribution. Isarithmic maps use lines to connect points of equal value; these lines are called isopleths, or isolines. Isopleths used for a particular phenomenon may have a particular name; for example, isotherms connect points of equal temperature , isobars connect points of equal air pressure, and

isohyets connect points of equal precipitation . Isopleths indicating differences in elevation are called contour lines. Isopleths are used to show how certain quantities change with location.

A topographic map is a good example of how isopleths are used to present information. Topographic maps use isopleths called contour lines to indicate variations in relief. Each contour line connects points of the same elevation. Adjacent lines indicate variations in relief; these variations are called contour intervals. The contour interval is indicated in the map legend. A contour interval of 20 ft (6.1 m) means that there is a 20 ft (6.1 m) difference in elevation between the points connected by one contour line and the points connected by the adjacent contour line. The closer the lines are to each other, the more dramatic the change in elevation.

Chloropleth maps are another type of thematic map. They use areas of graduated gray tones or a series of gradually intensifying colors to show spatial variations in the magnitude of a phenomenon. Greater magnitudes are symbolized by either darker gray tones or more intense colors; lesser magnitudes are indicated by lighter gray tones or less intense colors.

Cartographers traditionally obtained their information from navigators and surveyors. Explorations that expanded the geographical awareness of a map-making culture also resulted in increasingly sophisticated and accurate maps. Today, cartographers incorporate information from aerial photography and satellite imagery in the maps they create.

Modern cartographers face three major design challenges when creating a map. First, they must decide how to accurately portray that portion of Earth's surface that the map will represent; that is, they must figure out how to represent three-dimensional objects in two dimensions. Second, cartographers must represent geographic relationships at a reduced size while maintaining their proportional relationships. Third, they must select which pieces of information will be included in the map, and develop a system of generalization, which will make the information presented by the map useful and accessible to its readers.

When creating a flat map of a portion of the earth's surface, cartographers first locate their specific area of interest using latitude and longitude . They then use map projection techniques to represent the three-dimensional characteristics of that area in two dimensions. Finally, a grid, called a rectangular coordinate system, may be superimposed on the map, making it easier to use.

Distance and direction are used to describe the position of something in space , its location. In conversation, terms like right and left, up and down, or here and there are used to indicate direction and distance. These terms are useful only if the location of the speaker is known; in other words, they are relative. Cartographers, however, need objective terms for describing location The system of latitude and longitude, a geographical coordinate system developed by the Greeks, is used by cartographers for describing location.

Earth is a sphere, rotating around an axis tilted approximately 23.5 degrees off the perpendicular. The two points where the axis intersects the earth's surface are called the poles. The equator is an imaginary circle drawn around the center of the earth, equidistant from both poles. A plane that sliced through the earth at the equator would intersect the axis of the earth at a right angle. Lines drawn around the earth to the north and south of the equator and at right angles to the earth's axis are called parallels. Any point on the earth's surface is located on a parallel.

An arc is established when an angle is drawn from the equator to the axis and then north or south to a parallel. Latitude is the measurement of this arc in degrees. There are 90 degrees from the equator to each pole, and sixty minutes in each degree. Latitude is used to determine distance and direction north and south of the equator.

Meridians are lines running from the north pole to the south pole, dividing the earth's surface into sections, like those of an orange. Meridians intersect parallels at right angles, creating a grid. Just as the equator acts as the line from which to measure north or south, a particular meridian, called the prime meridian, acts as the line from which to measure east or west. There is no meridian that has a natural basis for being considered the prime meridian. The prime meridian is established by international agreement; currently, it runs through the Royal Observatory in Greenwich, England. Longitude is the measurement in degrees of the arc created by an angle drawn from the prime meridian to the earth's axis and then east or west to a meridian. There are 180° west of the prime meridian and 180° east of it. The international date line lies approximately where the 180th meridian passes through the Pacific Ocean.

Using the geographical coordinate system of latitude and longitude, any point on the earth's surface can be located with precision. For example, Buenos Aires, the capital of Argentina, is located 34° 35 minutes south of the equator and 58° 22 minutes west of the prime meridian; Anchorage, the largest city of the state of Alaska, is located 61° 10 minutes north of the equator and 149°s 45 minutes west of the prime meridian.

After locating their area of interest using latitude and longitude, cartographers must determine how best to represent that particular portion of the earth's surface in two dimensions. They must do this in such a way that minimal amounts of distortion affect the geographic information the map is designed to convey.

Cartographers have developed map projections as a means for translating geographic information from a spherical surface onto a planar surface. A map projection is a method for representing a curved surface, such as the surface of the earth, on a flat surface, such as a piece of paper, so that each point on the curved surface corresponds to only one point on the flat surface.

There are many types of map projections. Some of them are based on geometry, others are based on mathematical formulas. None of them, however, can accurately represent all aspects of the earth's surface; inevitably there will be some distortion in shape, distance, direction or area. Each type of map projection is intended to reduce the distortion of a particular spatial element. Some projections reduce directional distortion, others try to present shapes or areas in as distortion-free a manner as possible. The cartographer must decide which of the many projections available will provide the most distortion-free presentation of the information to be mapped.

Maps present various pieces of geographical information at a reduced scale. In order for the information to be useful to the map reader, the relative proportions of geographic features and spatial relationships must be kept as accurate as possible. Cartographers use various types of scales to keep those features and relationships in the correct proportions.

No single map can accurately show every feature on the earth's surface. There is simply too much spatial information at any particular point on the earth's surface for all of the information to be presented in a comprehensible, usable format. In addition, the process of reduction has certain visual effects on geographic features and spatial relationships. Because every feature is reduced by the ratio of the reduction, the distance between features is reduced, crowding them closer together and lessening the clarity of the image. The width and length of individual features are also reduced.

See also Earth (planet); Topography and topographic maps; Weather forecasting methods

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Cartography

Cartography

Cartography is the art of making maps. A map is a two-dimensional (flat) drawing or chart showing the political boundaries and physical features of a geographical region. For example, a map may show the location of cities, mountain ranges, and rivers, or may show the types of rock in a given region. Cartography is considered a subdiscipline of geography, which is the study of Earth's surface and its various climates, continents, countries, and resources.

The history of cartography

The oldest known map is of an area in northern Mesopotamia, an ancient region in southwest Asia. The baked clay tablet, found near present-day Nuzi, Iraq, dates from approximately 3800 b.c. Fragments of clay maps nearly 4,000 years old have been found in other parts of Mesopotamia, some showing city plans and others showing parcels of land. Over 3,000 years ago, the ancient Egyptians surveyed the lands in the Nile Valley. They drew detailed maps on papyrus for use in taxation.

The ancient Greeks developed many of the basic principles of modern cartography, including latitude and longitude, and map projections. The maps of Ptolemy, a Greek astronomer and mathematician who lived in the second century a.d., are considered the high point of Greek cartography.

The era of European exploration that arose in the 1500s supplied cartographers with a wealth of new information, which allowed them to produce maps and navigation charts of ever-increasing accuracy and detail. Europeans became fascinated with the idea of mapping the world. The French initiated the first national survey during the 1700s, and soon other European countries followed suit. Today, most countries have an official organization devoted to cartographic research and production.

Mapmaking

No single map can accurately show every feature on Earth's surface. There is simply too much spatial information at any particular point

for all of the information to be presented in a comprehensible, usable format. Maps show the location of selected phenomena by using symbols that are identified in a legend.

Maps are smaller than the area they depict: they present various pieces of geographical information at a reduced scale. Every map has a statement of its scale, which is an expression of the ratio between map distance and actual distance. This statement can take many forms, and many maps express scale in more than one way. The graphic scale is a line or bar showing how many actual miles or kilometers are represented by a particular number of inches or centimeters on the map. Another scale indicates distance as a ratio between two points on the map and their actual geographical distance. For example, a map with a scale of 1:100,000 tells the map reader that every 1 unit of distance on the map equals 100,000 of the same units of distance on the ground. In this example, 1 inch or centimeter on the map would equal 100,000 inches or centimeters in actual ground distance.

Cartographers traditionally obtained their information from navigators and surveyors. For many centuries maps were produced entirely by hand. They were drawn or painted on paper, hide, parchment, clay tablets, and slabs of wood. Each map was an original work. Once the printing press was developed in Europe in the 1400s, many reproductions were made from an original work. Maps became more common and more accessible.

Various techniques were integrated into the printing process during the last 200 years, increasing the variety of scales at which maps were produced. The introduction of the lithographic printing method in the late 1800s brought about the production of multicolored maps. Today, cartographers incorporate information from aerial photography and satellite imagery in the maps they create. They also use computer-assisted design programs to produce map images.

[See also Geologic map ]

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GIS (Geographic Information System)

GIS (Geographic Information System)


A geographic information system (GIS) is an integrated computer system that allows the storage, mapping, manipulation, and analysis of geographic or spatial data. It can present many different layers of information, all of which may be turned on or off depending on the user's needs. Several components are required for a GIS to function properly. A GIS typically consists of computer hardware, software, and the people operating the system, as well as the spatial or geographic data being manipulated.

A GIS works by storing a number of different data sets that each have geographical references. The various data for any given geographic location can then be integrated based on the user's needs. A powerful feature of GIS is that data from different sources may be combined into the same database and integrated in order to make it useful for several purposes. The U.S. Environmental Protection Agency (EPA) makes a dynamic GIS system available on its Web site that allows one to search and integrate information from several databases to create a map of pollution sources in his or her neighborhood.

GIS is a valuable tool that is commonly used by engineers, scientists, government officials, geographers, planners, environmental modelers, geologists, epidemiologists, and others. Professionals in these fields may use GIS on a regular basis for the analysis, mapping, and integration of geographical data. GIS incorporates geography through the review of spatial distribution, land features, and location, by referencing data such as an address, parcel identifier, or latitude/longitude. Approximately 85 to 90 percent of government agencies require the evaluation of geographic data and use of a GIS. Problems related to location, proximity, trends, and patterns are typically addressed by using a GIS. It also has modeling capabilities that allow specific scenarios and situations to be evaluated and used in decision-making processes.

Examples of GIS applications in state and local government agencies include land records management, land use planning, scientific/environmental investigations, infrastructure management, and natural resources planning and management. GIS is an extremely valuable analytical tool for professionals, providing support for decision-making processes, such as determining if a site is suitable for a future landfill, calculating the soil erosion potential in a specific region, or determining the best location for remediation treatment systems for contaminated groundwater plumes. GIS is frequently used by environmental engineers and other professionals to produce and maintain maps for sites they may be working on, watershed analyses, hydrologic studies, and many other applications.

Bibliography

Fairchild, Michael F.; Parks, Bradley O.; and Steyaert, Louis T. (1993). Environmental Modeling with GIS. New York: Oxford University Press.


Internet Resources

GeoCommunity. "GIS Data Depot." Available from http://www.gisdatadepot.com.

"National Center for Geographic Information & Analysis Core Curriculum in Geo-science." Available from http://www.ncgia.ucsb.edu/education.

U.S. Department of the Interior, U.S. Geological Survey Web site. Available from http://www.usgs.gov/research.

U.S. Environmental Protection Agency. "Enviromapper." Available from http://www.epa.gov/enviro.

Margrit von Braun and Deena Lilya

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GIS

GIS

K. LEE LERNER

GIS is the common abbreviation for Geographic Information Systems, a powerful and widely used computer database and software program that allows scientists to link geographically referenced information related to any number of variables to a map of a geographical area. GIS allows its users to analyze and display data using digitized maps. In addition, GIS can generate maps and tables useful to a wide-range of applications involving planning and decision-making. GIS programs allow the rapid storage, manipulation, and correlation of geographically referenced data (i.e., data tied to a particular point or latitude and longitude intersection on a map).

In addition to scientific studies, by 2003, GIS programs were in wide use in a number of emergency support agencies and systems (e.g., the Federal Emergency Management Agency (FEMA)).

GIS programs allow scientists to layer information so that different combinations of data plots can be assigned to the same defined area. GIS also allows users to manipulate data plots to predict changes or to interpret the evolution of historical data.

GIS maps are able to convey the same information as conventional maps, including the locations of rivers, roads, topographical features, and geopolitical information (e.g., location of cites, political boundaries, etc.). In addition, to conventional map features, GIS offers geologists, geographers, and other scholars the opportunity to selectively overlay data tied to geographic position. By overlaying different sets of data, scientists can look for points or patterns of correspondence. For example, rainfall data can be layered over another data layer describing terrain features. Over these layers, another layer data representing soil contamination data might be used to identify sources of pollution. In many cases, the identification of data correspondence spurs additional study for potential causal relationships.

GIS software data plots (e.g., sets of data describing roads, elevations, stream beds, etc.) are arranged in layers that can be selectively turned on or turned off.

NASA engineers and teams of other scientistsincluding researchers and undergraduates from Stephen F. Austin University in Nacogdoches, Texasemployed GIS mapping to map remains found after the break up of the space shuttle Columbia in January 2003. Debris field maps helped narrow search patterns andby linking the location of debrisallowed engineers and investigators to reconstruct critical elements of the disaster sequence. GPS data were used to construct the debris maps and to provide accurate representations of the retrogressive pattern of debris impacts.

GIS technology can also aid epidemiologists in tracking diseases and would be instrumental in the early identification of patterns of disease that could reveal a bioterrorist attack.

FURTHER READING:

BOOKS:

Rigaux, P. et al. Spatial Databases: With Application to GIS. Morgan Kaufmann, 2001.

Steede-Terry, K. Integrating GIS and the Global Positioning System. ESRI Press, 2000.

SEE ALSO

Forensic Geology in Military or Intelligence Operations
Geologic and Topographical Influences on Military and Intelligence Operations
Geospatial Imagery

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cartography

car·tog·ra·phy / kärˈtägrəfē/ • n. the science or practice of drawing maps. DERIVATIVES: car·tog·ra·pher / -fər/ n. car·to·graph·ic / ˌkärtəˈgrafik/ adj. car·to·graph·i·cal / ˌkärtəˈgrafikəl/ adj. car·to·graph·i·cal·ly / ˌkärtəˈgrafik(ə)lē/ adv.

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cartography

cartography XIX. — F. cartographie, f. carte map — L. charta CHART; see -O-, -GRAPHY.

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thematic map

thematic map In remote sensing, an image which has a classification overlaid on to it.

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cartography

cartography: see map.

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cartography

cartography. See maps.

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cartography

cartographydaffy, taffy •Amalfi •Cavafy, Gaddafi •Effie •beefy, Fifi, leafy •cliffy, iffy, jiffy, Liffey, niffy, sniffy, spiffy, squiffy, stiffy, whiffy •salsify •coffee, toffee •wharfie •Sophie, strophe, trophy •Dufy, goofy, Sufi •fluffy, huffy, puffy, roughie, roughy, scruffy, snuffy, stuffy, toughie •comfy • atrophy •anastrophe, catastrophe •calligraphy, epigraphy, tachygraphy •dystrophy, epistrophe •autobiography, bibliography, biography, cardiography, cartography, chirography, choreography, chromatography, cinematography, cosmography, cryptography, demography, discography, filmography, geography, hagiography, historiography, hydrography, iconography, lexicography, lithography, oceanography, orthography, palaeography (US paleography), photography, pornography, radiography, reprography, stenography, topography, typography •apostrophe •gymnosophy, philosophy, theosophy •furphy, murphy, scurfy, surfy, turfy

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