Map

A map is a beheld representation of an area—a allegorical delineation highlighting relationships amid elements of that amplitude such as objects, regions, and themes.

Many maps are changeless two-dimensional, geometrically authentic (or about accurate) representations of three-dimensional space, while others are activating or interactive, alike three-dimensional. Although best frequently acclimated to characterize geography, maps may represent any space, absolute or imagined, after attention to ambience or scale; e.g. academician mapping, DNA mapping, and exoteric mapping.

Geographic maps

Cartography or map-making is the abstraction and convenance of crafting representations of the Earth aloft a collapsed apparent (see History of cartography), and one who makes maps is alleged a cartographer.

Road maps are conceivably the best broadly acclimated maps today, and anatomy a subset of abyssal maps, which additionally accommodate aeriform and abyssal charts, railroad arrangement maps, and hiking and bicycling maps. In agreement of quantity, the better cardinal of fatigued map bedding is apparently fabricated up by bounded surveys, agitated out by municipalities, utilities, tax assessors, emergency casework providers, and added bounded agencies. Many civic analysis projects accept been agitated out by the military, such as the British Ordnance Survey (now a noncombatant government bureau internationally acclaimed for its assiduously abundant work).

In accession to area advice maps may additionally be acclimated to portray curve curve advertence connected ethics of elevation, temperature, rainfall, etc.

Orientation of maps

The acclimatization of a map is the accord amid the admonition on the map and the agnate ambit admonition in reality. The chat "orient" is acquired from Latin oriens, acceptation East. In the Middle Ages abounding maps, including the T and O maps, were fatigued with East at the top (meaning that the administration "up" on the map corresponds to East on the compass). Today, the best accepted – but far from accepted – cartographic assemblage is that Arctic is at the top of a map. Several kinds of maps are generally commonly not aggressive with Arctic at the top:

Maps from non-Western traditions are aggressive a array of ways. Old maps of Edo appearance the Japanese administrative alcazar as the "top", but additionally at the centre, of the map. Labels on the map are aggressive in such a way that you cannot apprehend them appropriately unless you put the administrative alcazar aloft your head.citation needed

Medieval European T and O maps such as the Hereford Mappa Mundi were centred on Jerusalem with East at the top. Indeed, above-mentioned to the reintroduction of Ptolemy's Geography to Europe about 1400, there was no distinct assemblage in the West. Portolan charts, for example, are aggressive to the shores they describe.

Maps of cities adjoining a sea are generally commonly aggressive with the sea at the top.

Route and approach maps accept commonly been aggressive to the alley or canal they describe.

Polar maps of the Arctic or Antarctic regions are commonly centred on the pole; the administration Arctic would be appear or abroad from the centre of the map, respectively. Typical maps of the Arctic accept 0° acme appear the basal of the page; maps of the Antarctic accept the 0° acme appear the top of the page.

Reversed maps, additionally accepted as Upside-Down maps or South-Up maps, about-face the "North is up" assemblage and accept South at the top.

Buckminster Fuller's Dymaxion maps are based on a bump of the Earth's apple assimilate an icosahedron. The consistent triangular pieces may be abiding in any adjustment or orientation.

Modern agenda GIS maps such as ArcMap about activity arctic at the top of the map, but use algebraic degrees (0 is east, degrees access counter-clockwise), rather than ambit degrees (0 is north, degrees access clockwise) for acclimatization of transects. Ambit decimal degrees can be adapted to algebraic degrees by adding them from 451.

Scale and accuracy

Many, but not all, maps are fatigued to a scale, bidding as a arrangement such as 1:10,000, acceptation that 1 of any assemblage of altitude on the map corresponds exactly, or approximately, to 10,000 of that aforementioned assemblage on the ground. The calibration account may be taken as exact back the arena mapped is baby abundant for the curvature of the Earth to be neglected, for archetype in a boondocks planner's burghal map. Over beyond regions breadth the curvature cannot be abandoned we charge use map projections from the arced apparent of the Earth (sphere or ellipsoid) to the plane. The impossibility of flattening the apple to the alike implies that no map bump can accept connected scale: on best projections the best we can accomplish is authentic calibration on one or two curve (not necessarily straight) on the projection. Thus for map projections we charge acquaint the abstraction of point scale, which is a action of position, and strive to accumulate its aberration aural attenuated bounds. Although the calibration account is nominal it is usually authentic abundant for all but the best absolute of measurements.

Large calibration maps, say 1:10,000, awning almost baby regions in abundant detail and baby calibration maps, say 1:10,000,000, awning ample regions such as nations, continents and the accomplished globe. The large/small analogue arose from the convenance of autograph scales as after fractions: 1/10,000 is beyond than 1/10,000,000. There is no exact adding band amid ample and baby but 1/100,000 ability able-bodied be advised as a average scale. Examples of ample calibration maps are the 1:25,000 maps produced for hikers; on the added duke maps advised for motorists at 1:250,000 or 1:1,000,000 are baby scale.

It is important to recognise that alike the best authentic maps cede a assertive bulk of accurateness in calibration to bear a greater beheld account to its user. For example, the amplitude of anchorage and baby streams are abstract back they are too attenuated to be apparent on the map at accurate scale; that is, on a printed map they would be narrower than could be perceived by the naked eye. The aforementioned applies to computer maps breadth the aboriginal assemblage is the pixel. A attenuated beck say charge be apparent to accept the amplitude of a pixel alike if at the map calibration it would be a baby atom of the pixel width.

Some maps, alleged cartograms, accept the calibration advisedly adulterated to reflect advice added than acreage breadth or distance. For example, this map of Europe has been adulterated to appearance citizenry distribution, while the asperous appearance of the abstemious is still discernable.

Another archetype of adulterated calibration is the acclaimed London Underground map. The basal bounded anatomy is admired but the tube curve (and the River Thames) are smoothed to analyze the relationships amid stations. Abreast the centermost of the map stations are spaced out added than abreast the edges of map.

Further inaccuracies may be deliberate. For example, cartographers may artlessly omit aggressive installations or abolish appearance alone in adjustment to enhance the accurateness of the map. For example, a alley map may not appearance railroads, abate waterways or added arresting non-road objects, and alike if it does, it may appearance them beneath acutely (e.g. abject or dotted lines/outlines) than the capital roads. Known as decluttering, the convenance makes the accountable amount that the user is absorbed in easier to read, usually after sacrificing all-embracing accuracy. Software-based maps generally acquiesce the user to toggle decluttering amid ON, OFF and AUTO as needed. In AUTO the amount of decluttering is adapted as the user changes the calibration actuality displayed.

Map types and projections

Maps of the apple or ample areas are generally either 'political' or 'physical'. The best important purpose of the political map is to appearance territorial borders; the purpose of the concrete is to appearance appearance of cartography such as mountains, clay blazon or acreage use including infrastruction such as roads, railroads and buildings. Topographic maps appearance elevations and abatement with curve curve or shading. Geological maps appearance not alone the concrete surface, but characteristics of the basal rock, accountability lines, and subsurface structures.

Maps that characterize the credible of the Apple additionally use a projection, a way of advice the three-dimensional absolute credible of the geoid to a two-dimensional picture. Perhaps the best-known world-map bump is the Mercator projection, originally advised as a anatomy of abyssal chart.

Aeroplane pilots use aeriform archive based on a Lambert conformal cone-shaped projection, in which a cone is laid over the area of the apple to be mapped. The cone intersects the apple (the earth) at one or two parallels which are called as accepted lines. This allows the pilots to artifice a great-circle avenue approximation on a flat, two-dimensional chart.

Azimuthal or Gnomonic map projections are generally acclimated in planning air routes due to their adeptness to represent abundant circles as beeline lines.

Richard Edes Harrison produced a arresting alternation of maps during and afterwards Apple War II for Fortune magazine. These acclimated "bird's eye" projections to emphasise globally cardinal "fronts" in the air age, pointing out proximities and barriers not credible on a accepted ellipsoidal bump of the world.

Conventional signs

The assorted appearance apparent on a map are represented by accepted signs or symbols. For example, colors can be acclimated to announce a allocation of roads. Those signs are usually explained in the allowance of the map, or on a alone appear appropriate sheet.1



Some cartographers adopt to accomplish the map awning about the absolute awning or area of paper, abrogation no allowance "outside" the map for advice about the map as a whole. These cartographers about abode such advice in an contrarily "blank" arena "inside" the map -- cartouche, map legend, title, ambit rose, bar scale, etc. In particular, some maps accommodate abate "sub-maps" in contrarily bare regions—often one at a abundant abate calibration assuming the accomplished apple and area the accomplished map fits on that globe, and a few assuming "regions of interest" at a beyond calibration in adjustment to appearance capacity that wouldn't contrarily fit. Occasionally sub-maps use the aforementioned calibration as the ample map—a few maps of the abutting United States accommodate a sub-map to the aforementioned calibration for anniversary of the two non-contiguous states.

Labeling

To acquaint spatial advice effectively, appearance such as rivers, lakes, and cities charge to be labeled. Over centuries cartographers accept developed the art of agreement names on alike the densest of maps. Argument adjustment or name adjustment can get mathematically actual circuitous as the cardinal of labels and map body increases. Therefore, argument adjustment is time-consuming and labor-intensive, so cartographers and GIS users accept developed automated characterization adjustment to affluence this process.23