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A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes.
Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although most commonly used to depict geography, maps may represent any space, real or imagined, without regard to context or scale, such as in brain mapping, DNA mapping, or computer network topology mapping. The space being mapped may be two dimensional, such as the surface of the earth, three dimensional, such as the interior of the earth, or even more abstract spaces of any dimension, such as arise in modeling phenomena having many independent variables.
Although the earliest maps known are of the heavens, geographic maps of territory have a very long tradition and exist from ancient times. The word “map” comes from the medieval Latin Mappa mundi, wherein mappa meant napkin or cloth and mundi the world. Thus, “map” became the shortened term referring to a two-dimensional representation of the surface of the world.
Cartography or map-making is the study and practice of crafting representations of the Earth upon a flat surface (see History of cartography), and one who makes maps is called a cartographer.
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 municipalities, utilities, tax assessors, emergency services providers, and other local agencies. Many national surveying projects have been carried out by the military, such as the British Ordnance Survey: a civilian government agency, internationally renowned for its comprehensively detailed work.
In addition to location information maps may also be used to portray contour lines indicating constant values of elevation, temperature,
The orientation of a map is the relationship between the directions on the map and the corresponding compass directions in reality. The word “orient” is derived from Latin oriens, meaning east. In the Middle Ages many maps, including the T and O maps, were drawn with east at the top (meaning that the direction “up” on the map corresponds to East on the compass). The most common cartographic convention is that north is at the top of a map.
Maps not oriented with north at the top:
Maps from non-Western traditions are oriented a variety of ways. Old maps of Edo show the Japanese imperial palace 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.
Maps of cities bordering a sea are often conventionally oriented with the sea at the top.
Route and channel maps have traditionally been oriented to the road or waterway they describe.
Polar maps of the Arctic or Antarctic regions are conventionally centred on the pole; the direction North would be towards or away from the centre of the map, respectively. Typical maps of the Arctic have 0° meridian towards the bottom of the page; maps of the Antarctic have the 0° meridian towards the top of the page.
Reversed maps, also known as Upside-Down maps or South-Up maps, reverse the North is up convention and have south at the top.
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.
Modern digital GIS maps such as ArcMap typically project north at the top of the map, but use math degrees (0 is east, degrees increase counter-clockwise), rather than compass degrees (0 is north, degrees increase clockwise) for orientation of transects. Compass decimal degrees can be converted to math degrees by subtracting them from 450; if the answer is greater than 360, subtract 360.
Many maps are drawn to a scale expressed as a ratio, such as 1:10,000, which means that 1 unit of measurement on the map corresponds to 10,000 of that same unit on the ground. The scale statement can be accurate when the region mapped is small enough for the curvature of the Earth to be neglected, such as a city map. Mapping larger regions, where curvature cannot be ignored, requires projections to map from the curved surface of the Earth to the plane. The impossibility of flattening the sphere to the plane without distortion means that the map cannot have constant scale. Rather, on most projections the best that can be attained is accurate scale along one or tw