MAP

graphic representation, drawn to scale and usually on a flat surface, of featuresusually geographical, geological, or geopoliticalof an area of the Earth or of any other celestial body. Globes are maps represented on the surface of a sphere. Cartography is the art and science of making maps and charts. Major types of maps include topographical maps, showing features of the Earth's land surface; nautical charts, representing coastal and marine areas; hydrographic charts, which specify ocean depths and the directions and intensities of oceanic currents; and aeronautical charts, which detail surface features and air routes. graphic representation, drawn to scale and usually on a flat surface, of featuresfor example, geographical, geological, or geopoliticalof an area of the Earth or of any other celestial body. Globes are maps represented on the surface of a sphere. Cartography is the art and science of making maps and charts. In order to imply the elements of accurate relationships, and some formal method of projecting the spherical subject to a map plane, further qualifications might be applied to the definition. The tedious and somewhat abstract statements resulting from attempts to formulate precise definitions of maps and charts are more likely to confuse than to clarify. The words map, chart, and plat are used somewhat interchangeably. The connotations of use, however, are distinctive: charts for navigation purposes (nautical and aeronautical), plats (in a property-boundary sense) for land-line references and ownership, and maps for general reference. Cartography is allied with geography in its concern with the broader aspects of the Earth and its life. In early times cartographic efforts were more artistic than scientific and factual. As man explored and recorded his environment, the quality of his maps and charts improved. These lines of Jonathan Swift were inspired by early maps: So geographers, in Afric maps, With savage pictures fill their gaps, And o'er unhabitable downs Place elephants for want of towns. Topographic maps are graphic representations of natural and man-made features of parts of the Earth's surface plotted to scale. They show the shape of land and record elevations above sea level, lakes, streams and other hydrographic features, and roads and other works of man. In short, they provide a complete inventory of the terrain and important information for all activities involving the use and development of the land. They provide the bases for specialized maps and data for compilation of generalized maps of smaller scale. Nautical charts are maps of coastal and marine areas, providing information for navigation. They include depth curves or soundings or both; aids to navigation such as buoys, channel markers, and lights; islands, rocks, wrecks, reefs and other hazards; and significant features of the coastal areas, including promontories, church steeples, water towers, and other features helpful in determining positions from offshore. The terms hydrography and hydrographer date from the mid-16th century; their focus has become restricted to studies of ocean depths and of the directions and intensities of oceanic currents; though at various times they embraced much of the sciences now called hydrology and oceanography. The British East India Company employed hydrographers in the 18th century, and the first hydrographer of the Royal Navy, Alexander Dalrymple (17371808), was appointed in 1795. A naval observatory and hydrographic office was established administratively in the United States Navy in 1854. In 1866 a hydrographic office was established by statute, and in 1962 it was renamed the U.S. Naval Oceanographic Office. Interest in the charting of oceanic areas away from seacoasts developed in the second half of the 19th century, concurrently with the perfection of submarine cables. As knowledge of the configuration of the ocean basins increased, the attention of scientists was drawn to this field of study. A feature of marine science since the 1950s has been increasingly detailed bathymetric (water-depth measurement) surveys of selected portions of the seafloor. Together with collection of associated geophysical data and sampling of sediments, these studies assist in interpreting the geologic history of the ocean-covered portion of the Earth's crust. Aeronautical charts provide essential data for the pilot and air navigator. They are, in effect, small-scale topographic maps on which current information on aids to navigation have been superimposed. To facilitate rapid recognition and orientation, principal features of the land that would be visible from an aircraft in flight are shown to the exclusion of less important details. Elements Map design is a twofold process: (1) the determination of user requirements, with attendant decisions as to map content and detail, and (2) the arrangement of content, involving publication scale, standards of treatment, symbolizations, colours, style, and other factors. To some extent user requirements obviously affect standards of treatment, such as publication scale. Otherwise, the latter elements are largely determined on the basis of efficiency, legibility, aesthetic considerations, and traditional practices. In earlier productions by individual cartographers or small groups, personal judgments determined the nature of the end product, usually with due respect for conventional standards. Map design for large programs, such as the various national map series of today, is quite formal by comparison. In most countries, the requirements of official as well as private users are carefully studied, in conjunction with costs and related factors, when considering possible changes or additions to the current standards. Requirements of military agencies often have a decisive influence on map design, since it is desirable to avoid the expense of maintaining both civil and military editions of maps. International organizations and committees are additional factors in determining map design. The fact that development of changes in design and content of national map series may become rather involved induces some reluctance to change, as does the fact that map stocks are usually printed in quantities intended to last for 10 or more years. Also, frequent changes in treatments result in extensive overhauls at reprint time, with consequent inconsistencies among the standing editions. Planning for the production of a national series involves both technical and program considerations. Technical planning involves the choice of a contour interval (the elevation separating adjacent contour lines, or lines of constant elevation), which in turn determines the height of aerial photography and other technical specifications for each project. The sequence of mapping steps, or operational phases, is determined by the overall technical procedures that have been established to achieve the most efficiency. The program aspects of planning involve fiscal allotments, priorities, schedules, and related matters. Production controls also play important roles in large programs, where schedules must be balanced with capacities available in the respective phases to avoid backlogs or dormant periods between the mapping steps. Considering that topographic maps may require two years or more to complete, from authorization to final printing, the importance of careful planning is evident. Many factors, including the weather, can converge to cause delays. Map scales and classifications Map scale refers to the size of the representation on the map as compared to the size of the object on the ground. The scale generally used in architectural drawings, for example, is 1/4 inch to one foot, which means that 1/4 of an inch on the drawing equals one foot on the building being drawn. The scales of models of buildings, railroads, and other objects may be one inch to several feet. Maps cover more extensive areas, and it is usually convenient to express the scale by a representative fraction or proportion, as 1/63,360, 1:63,360, or one-inch-to-one-mile. The scale of a map is smaller than that of another map when its scale denominator is larger: thus, 1:1,000,000 is a smaller scale than 1:100,000. Most maps carry linear, or bar, scales in one or more margins or in the title blocks. Nautical charts are constructed on widely different scales and can be generally classified as follows: ocean sailing charts are small-scale charts, 1:5,000,000 or smaller, used for planning long voyages or marking the daily progress of a ship. Sailing charts, used for offshore navigation, show a generalized shoreline, only offshore soundings, and are at a scale between 1:600,000 and 1:5,000,000. As an illustration of chart use, a 10-knot ship covers about 29 inches (74 centimetres) at 1:600,000 scale in a day. General charts are used for coastwise navigation outside outlying reefs and shoals and are at a scale between 1:100,000 and 1:600,000. Coast charts are intended for use in leaving and entering port or navigating inside outlying reefs or shoals and are at a scale between 1:50,000 and 1:100,000. Harbour charts are for use in harbours and small waterways, with a scale usually larger than 1:50,000. In rare instances reference may be made to the areal scale of a map, as opposed to the more common linear scale. In such cases the denominator of the fractional reference would be the square of the denominator of the linear scale. The linear scale may vary within a single map, particularly if the scale is small. Variations in the scale of a map because of the sphericity of the surface it represents may, for practical purposes, be considered as nil. On maps of very large scale, such as 1:24,000, such distortions are negligible (considerably less than variations in the paper from fluctuations of humidity). Precise measurements for engineering purposes are usually restricted to maps of that scale or larger. As maps descend in scale, and distortions inherent to their projection of the spherical surface increase, less accurate measurements of distances may be expected. Maps may be classified according to scale, content, or derivation. The latter refers to whether a map represents an original survey or has been derived from other maps or source data. Some contain both original and derived elements, usually explained in their footnotes. Producing agencies, technical committees, and international organizations have variously classed maps as large, medium, or small scale. In general, large scale means inch-to-mile and larger, small scale, 1:1,000,000 and smaller, leaving the intermediate field as medium scale. As with most relative terms, these can occasionally lead to confusions but are useful as one practical way to classify maps. The nature of a map's content, as well as its purpose, provides a primary basis of classification. The terms aeronautical chart, geologic, soil, forest, road, and weather map make obvious their respective contents and purposes. Maps are therefore often classified by the primary purposes they serve. Topographic maps usually form the background for geologic, soil, and similar thematic maps and provide primary elements of the bases upon which many other kinds of maps are compiled. Additional reading History of cartography A list of sources on the topic is presented in Walter W. Ristow, Guide to the History of Cartography: An Annotated List of References on the History of Maps and Mapmaking (1973). Robert C. Duru, Maps and Map Making (1977); and G.R. Crone, Maps and Their Makers: An Introduction to the History of Cartography, 5th ed. (1978), are brief overviews. Essential aspects are explored in Leo Bagrow, History of Cartography, 2nd ed., rev. by R.A. Skelton (1985, originally published in German, 1951); Charles Bricker, Landmarks of Mapmaking: An Illustrated Survey of Maps and Mapmakers (1968; also published as A History of Cartography: 2500 Years of Maps and Mapmakers, 1969; reissued 1977); Lloyd A. Brown, The Story of Maps (1949, reprinted 1979), and Map Making: The Art That Became a Science (1960); Edward Lynam, The Mapmaker's Art: Essays on the History of Maps (1953); and John Noble Wilford, The Mapmakers (1981). Maps of specific periods are studied in Charles H. Hapgood, Maps of the Ancient Sea Kings: Evidence of Advanced Civilization in the Ice Age, rev. ed. (1979); R.A. Skelton, Decorative Printed Maps of the 15th to 18th Centuries (1952, reprinted 1966); Hugh Cortazzi, Isles of Gold: Antique Maps of Japan (1983); and Raymond Lister, How to Identify Old Maps and Globes: With a List of Cartographers, Engravers, Publishers, and Printers Concerned with Printed Maps and Globes from c. 1500 to c. 1850 (1965).The development of cartographic institutions can be traced in Mary Blewitt, Surveys of the Seas: A Brief History of British Hydrography (1957); Sir Archibald Day, The Admiralty Hydrographic Service, 17951919 (1967); Adrian H.W. Robinson, Marine Cartography in Britain: A History of the Sea Chart to 1855 (1962); and G.S. Ritchie, The Admiralty Chart: British Naval Hydrography in the Nineteenth Century (1967). Mapmaking The procedures involved in creating a map are described in many books, including Wellman Chamberlin, The Round Earth on Flat Paper: Map Projections Used by Cartographers (1947); Arthur D. Merriman, An Introduction to Map Projections (1947); Erwin J. Raisz, General Cartography, 2nd ed. (1948), and Principles of Cartography (1962); Eduard Imhof, Cartographic Relief Presentation (1982; originally published in German, 1965); J.S. Keates, Cartographic Design and Production (1973); Arthur H. Robinson et al., Elements of Cartography, 5th ed. (1984); John Loxton, Practical Map Production (1980); and Morris M. Thompson, Maps for America: Cartographic Products of the U.S. Geological Survey and Others, 2nd ed. (1981). A range of special projects, of which cartography is an essential part, are described in A.H.A. Hogg, Surveying for Archaeologists and Other Fieldworkers (1980); Teodor J. Blachut, Adam Chrzanowski, and Jouko H. Saastamoinen, Urban Surveying and Mapping (1979); P.F. Dale, Cadastral Surveys Within the Commonwealth (1976); S. Rowton Simpson, Land Law and Registration (1976); R.A. Skelton, The Legal Elements of Boundaries and Adjacent Properties (1930); Curtis M. Brown, Walter G. Robillard, and Donald A. Wilson, Evidence and Procedures for Boundary Location, 2nd ed. (1981); T.W. Birch, Maps: Topographical and Statistical, 2nd ed. (1964, reprinted with corrections, 1976); B.W. Lucke, A Course on the Chart (1966); M. Chriss and G.R. Hayes, An Introduction to Charts and Their Use, 4th ed. (1977); and D.A. Moore, Marine Chartwork, 2nd ed. (1981). Technical developments The many special studies in the field include Chester C. Slama (ed.), Manual of Photogrammetry, 4th ed. (1980); John Wright, Ground and Air Survey for Field Scientists (1982); C.D. Burnside, Electromagnetic Distance Measurement, 2nd ed. (1982); and William Ritchie et al., Mapping for Field Scientists: A Problem-Solving Approach (1977). Current developments are covered in special journals: Surveying and Mapping (quarterly); Photogrammetria (bimonthly); Military Engineer (bimonthly); The American Cartographer (semiannual); Cartography (semiannual); and Cartographica (quarterly). Charles F. Fuechsel