Map

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A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes.

Many maps are static 2D geometric model of three-dimensional space, while others are dynamic or interactive, even three-dimensional. Although most commonly used to depict geography, maps may represent any space, real or imagined, without regard to context or scale; e.g. Brain mapping, DNA mapping, and extra-terrestrial mapping.

Geographic maps Cartography, or map-making is the study and, often, practice, of crafting representations of the Earth upon a flat surface (see History of cartography), and one who makes maps is called a cartographer.

While we tend to think of maps today as products of a rationalistic, scientific world-view, maps also have a mythical quality. Pre-modern maps, and mapping traditions outside the Western tradition, often merge geography with non-scientific cosmography, showing the relationship of the viewer to the universe. Medieval T-O map, for example, show Jerusalem at the centre of the and Bruno with his mention of a fictional map that had "the scale of a mile to the mile". A character notes some practical difficulties with this map and states that "we now use the country itself, as its own map, and I assure you it does nearly as well". This concept is elaborated in a one-paragraph story by Jorge Luis Borges, generally known in English language as "On Exactitude in Science".

Road maps are perhaps the most widely used maps today, and form a subset of navigational maps, which also include aeronautical and nautical charts, railroad network maps, and hiking and bicycling maps. In terms of quantity, the largest number of drawn map sheets is probably made up by local surveys, carried out by municipality, utilities, tax assessors, emergency services providers, and other local agencies. Many national surveying projects have been carried out by the military, such as the United Kingdom Ordnance Survey (now a civilian government agency internationally renowned for its comprehensively detailed work).

Orientation of maps , about 1300, Hereford Cathedral, England. A classic "T-O" map with Jerusalem at centre, east toward the top, Europe the bottom left and Africa on the right.

The term Orientation (physical) refers to the relationship between directions on a map and compass directions. The word orient is derived from oriens, meaning east. In the Middle Ages many maps, including the T and O maps, were drawn with east at the top. Today the most common, but far from universal, cartographic convention is that North is at the top of a map. Examples of maps not orientated to north are:

Polar maps of the Arctic or Antarctic regions are conventionally centered on the pole, in which case the direction north would be towards or away from the center of the map, respectively.
Buckminster Fuller's Dymaxion maps are based on a projection of the Earth's sphere onto an icosahedron. The resulting triangular pieces may be arranged in any order or orientation.
Maps from non-Western traditions are oriented a variety of ways. Old maps of Edo show the Kokyo as the "top," but also at the centre, of the map. Labels on the map are oriented in such a way that you cannot read them properly unless you put the imperial palace above your head.
Medieval European T and O maps such as the Hereford Mappa Mundi were centred on Jerusalem with east at the top. Indeed, prior to the reintroduction of Ptolemy's Geography to Europe around 1400, there was no single convention in the West. Portolan charts, for example, are oriented to the shores they describe.
Route and channel maps have traditionally been oriented to the road or waterway they describe.
Many maps used in the Society for Creative Anachronism show the west at the top, in honor of the Society starting in California.

Scale and accuracy Many but not all maps are drawn to a Scale (map), allowing the reader to infer the actual sizes of, and distances between, depicted objects. A larger scale shows more detail, thus requiring a larger map to show the same area. For example, maps designed for the hiker are often scaled at the ratio 1:24,000, meaning that 1 of any unit of measurement on the map corresponds to 24,000 of that same unit in reality; while maps designed for the motorist are often scaled at 1:250,000. Maps which use some quality other than physical area to determine relative size are called cartograms.

A famous example of a map without scale is the Tube map, which best fulfils its purpose by being less physically accurate and more visually communicative to the hurried glance of the commuter. This is not a cartogram (since there is no consistent measure of distance) but a Topology map that also depicts approximate bearings. The simple maps shown on some directional road signs are further examples of this kind.

In fact, most commercial navigational maps, such as road maps and town plans, sacrifice an amount of accuracy in scale to deliver a greater visual usefulness to its user, for example by exaggerating the width of roads. With the end-user similarly in mind, cartographers will censor the content of the space depicted by a map in order to provide a useful tool for that user.For example, a road map may or may not show railroads, and if it does, it may show them less clearly than highways.

Some maps such as topographical maps show constant values such as elevation, these are often represented, along with other characteristics, depending on the scale of the map, in the form of Isolines. Isolines on a map or chart indicate a constant value such as temperature, or rainfall.

World maps and projections )Maps of the world or large areas are often either 'political' or 'physical'. The most important purpose of the political map is to show territorial borders; the purpose of the physical is to show features of geography such as mountains, soil type or land use. Geological maps show not only the physical surface, but characteristics of the underlying rock, Geologic fault lines, and subsurface structures.

Maps that depict the surface of the Earth also use a map projection, a way of translating the three-dimensional real surface of the geoid to a two-dimensional picture. Perhaps the best-known world-map projection is the Mercator Projection, originally designed as a form of nautical chart.

Airplane pilots use aeronautical charts based on a Lambert conformal conic projection, in which a cone is laid over the section of the earth to be mapped. The cone intersects the sphere (the earth) at one or two parallels which are chosen as standard lines. This allows the pilots to plot a great-circle route approximation on a flat, two-dimensional chart.

Map projection#Azimuthal .28projections onto a plane.29 or Gnomonic projection map projections are often used in planning air routes due to their ability to represent great circles as straight lines.

Richard Edes Harrison produced a striking series of maps during and after World War II for Fortune magazine. These used "bird's eye" projections to emphasize globally strategic "fronts" in the air age, pointing out proximities and barriers not as apparent on a conventional rectangular projection of the world.

Electronic maps digital raster graphic.From the last quarter of the 20th century, the indispensable tool of the cartographer has been the computer. Much of cartography, especially at the data-gathering survey level, has been subsumed by geographic information system (GIS). The functionality of maps has been greatly advanced by technology allowing, for example, the superimposition of spatially located variables onto existing geographical maps. Having local information such as rainfall level, distribution of wildlife, or demographic data integrated within the map makes for more efficient analysis and better decision making. In the pre-electronic age such superimposition of data led to John Snow (physician) discovering the cause of cholera. Today, it is used by agencies as diverse as wildlife conservationists and militaries around the world.

Even when GIS is not involved, most cartographers now use a variety of computer graphics programs to generate new maps.

Interactive, computerised maps are commercially available, allowing users to zoom in or zoom out (respectively meaning to increase or decrease the scale), sometimes by replacing one map with another of different scale, centred where possible on the same point. In-car Satellite navigation are computerised maps with route-planning and advice facilities which monitor the user's position with the help of satellites. From the computer scientist's point of view, zooming in entails one or a combination of:

replacing the map by a more detailed one

enlarging the same map without enlarging the pixels, hence showing more detail by removing less information compared to the less detailed version

enlarging the same map with the pixels enlarged (replaced by rectangles of pixels); no additional detail is shown, but, depending on the quality of one's vision, possibly more detail can be seen; if a computer display does not show adjacent pixels really separate, but overlapping instead (this does not apply for an Liquid crystal display, but may apply for a cathode ray tube), then replacing a pixel by a rectangle of pixels does show more detail. A variation of this method is interpolation.

For example:

Typically (2) applies to a Portable Document Format (PDF) file. The increase in detail is, of course, limited to the information contained in the file: enlargement of a curve may eventually result in a series of standard geometric figures such as straight lines or arcs of circles.
(2) may apply to text and (3) to the outline of a map feature such as a forest or building.
(1) may apply to the text (displaying labels for more features), while (2) applies to the rest of the image. Text is not necessarily enlarged when zooming in. Similarly, a road represented by a double line may or may not become wider when one zooms in.
The map may also have layers which are partly raster graphics and partly vector graphics. For a single raster graphics image (2) applies until the pixels in the image file correspond to the pixels of the display, thereafter (3) applies.

See also Webpage#Graphics, Portable Document Format#Layers, Mapquest, Google Maps, Google Earth or Yahoo! Maps.

Labeling To communicate spatial information effectively, features such as rivers, lakes, cities and so on need to be labeled. Over centuries cartographers perfected the art of placing names on even the densest of maps. Text placement or name placement can get mathematically very complex as the number of labels and map density increases. Therefore, text placement is time-consuming and labor-intensive, which is why automatic label placement makes the life of cartographers and GIS users easier when it comes to labeling maps Imhof, E., “Die Anordnung der Namen in der Karte,” Annuaire International de Cartographie II, Orell-Füssli Verlag, Zürich, 93-129, 1962., Freeman, H.,, Map data processing and the annotation problem, Proc. 3rd Scandinavian Conf. on Image Analysis, Chartwell-Bratt Ltd. Copenhagen, 1983..

Footnotes

References

David Buisseret, ed., Monarchs, Ministers and Maps: The Emergence of Cartography as a Tool of Government in Early Modern Europe. Chicago: University of Chicago Press, 1992, ISBN 0-226-07987-2
Freeman, Herbert, Automated Cartographic Text Placement. White paper.
Ahn, J. and Freeman, H., “A program for automatic name placement,” Proc. AUTO-CARTO 6, Ottawa, 1983. 444-455.
Freeman, H., “Computer Name Placement,” ch. 29, in Geographical Information Systems, 1, D.J. Maguire, M.F. Goodchild, and D.W. Rhind, John Wiley, New York, 1991, 449-460.
Mark Monmonier, How to Lie with Maps, ISBN 0-226-53421-9
O'Connor, J.J. and E.F. Robertson, The History of Cartography. Scotland : St. Andrews University, 2002.
Denis E. Cosgrove (ed.) Mappings. Reaktion Books, 1999 ISBN 1-86189-021-4

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See also General

Atlas
Ancient world maps
Automatic label placement
Cartography
Geography
Globe
History of cartography
Template:Coord

Map design and types

Thematic map
Cartogram
Contour line
Dymaxion map
Floor plan
Geologic map
Map design
Nautical chart
Pictorial maps
Planform
Plat
Reversed map
Road atlas
Street map
Topographic map
World map

Modern maps

Map history

George Bradshaw, including maps of the British railway network, first published in 1839
Sanborn Maps - detailed American fire insurance maps
Ordnance Survey