Map Commune FR Insee Code 32316

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 fictional, 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 , wherein ''mappa'' meant 'napkin' or 'cloth' and ''mundi'' 'the world'. Thus, "map" became a shortened term referring to a two-dimensional representation of the surface of the world.

History

The history of cartography traces the development of cartography, or mapmaking technology, in human history. Maps have been one of the most important human inventions for millennia, allowing humans to explain and navigate their way through the world. The earliest surviving maps include cave paintings and etchings on tusk and stone, followed by extensive maps produced by ancient Babylon, Greece and Rome, China, and India. In their most simple form maps are two dimensional constructs, however since the age of Classical Greece maps have also been projected onto a three-dimensional sphere known as a globe. The Mercator Projection, developed by Flemish geographer Gerardus Mercator, was widely used as the standard two-dimensional projection of the earth for world maps until the late 20th century, when more accurate projections were formulated. Mercator was also the first to use and popularise the concept of the atlas as a collection of maps.

Geography

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, rainfall, etc.

Orientation

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 , 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 have oriented a variety of ways. Old maps of Edo show the Japanese imperial palace as the "top", but also at the center, 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 centered on Jerusalem with East at the top. Indeed, before 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 centered on the pole; the direction North would be toward or away from the center of the map, respectively. Typical maps of the Arctic have 0° meridian toward the bottom of the page; maps of the Antarctic have the 0° meridian toward the top of the page.
* South-up maps invert the ''North is up'' convention by having south at the top. Ancient Africans including in Ancient Egypt used this orientation, as some maps in Brazil do today.
* 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.
* Using the equator as the edge, the world map of Gott, Vanderbei, and Goldberg is arranged as a pair of disks back-to-back designed to present the least error possible. They are designed to be printed as a two-sided flat object that could be held easily for educational purposes.

Scale and accuracy

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 the 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 a constant scale. Rather, on most projections, the best that can be attained is an accurate scale along one or two paths on the projection. Because scale differs everywhere, it can only be measured meaningfully as point scale per location. Most maps strive to keep point scale variation within narrow bounds. Although the scale statement is nominal it is usually accurate enough for most purposes unless the map covers a large fraction of the earth. At the scope of a world map, scale as a single number is practically meaningless throughout most of the map. Instead, it usually refers to the scale along the equator.

Some maps, called cartograms, have the scale deliberately distorted to reflect information other than land area or distance. For example, this map (at the right) of Europe has been distorted to show population distribution, while the rough shape of the continent is still discernible.

Another example of distorted scale is the famous London Underground map. The basic geographical structure is respected but the tube lines (and the River Thames) are smoothed to clarify the relationships between stations. Near the center of the map, stations are spaced out more than near the edges of the map.

Further inaccuracies may be deliberate. For example, cartographers may simply omit military installations or remove features solely to enhance the clarity of the map. For example, a road map may not show railroads, smaller waterways, or other prominent non-road objects, and even if it does, it may show them less clearly (e.g. dashed or dotted lines/outlines) than the main roads. Known as decluttering, the practice makes the subject matter that the user is interested in easier to read, usually without sacrificing overall accuracy. Software-based maps often allow the user to toggle decluttering between ON, OFF, and AUTO as needed. In AUTO the degree of decluttering is adjusted as the user changes the scale being displayed.

Projection

Geographic maps use a projection to translate the three-dimensional real surface of the geoid to a two-dimensional picture. Projection always distorts the surface. There are many ways to apportion the distortion, and so there are many map projections. Which projection to use depends on the purpose of the map.

Symbology

The various features shown on a map are represented by conventional signs or symbols. For example, colors can be used to indicate a classification of roads. Those signs are usually explained in the margin of the map, or on a separately published characteristic sheet.

Some cartographers prefer to make the map cover practically the entire screen or sheet of paper, leaving no room "outside" the map for information about the map as a whole. These cartographers typically place such information in an otherwise "blank" region "inside" the mapcartouche, map legend, title, compass rose, bar scale, etc.
In particular, some maps contain smaller "sub-maps" in otherwise blank regions—often one at a much smaller scale showing the whole globe and where the whole map fits on that globe, and a few showing "regions of interest" at a larger scale to show details that wouldn't otherwise fit.
Occasionally sub-maps use the same scale as the large map—a few maps of the contiguous United States include a sub-map to the same scale for each of the two non-contiguous states.

Design

The design and production of maps is a craft that has developed over thousands of years, from clay tablets to Geographic information systems. As a form of Design, particularly closely related to Graphic design, map making incorporates scientific knowledge about how maps are used, integrated with principles of artistic expression, to create an aesthetically attractive product, carries an aura of authority, and functionally serves a particular purpose for an intended audience.

Designing a map involves bringing together a number of elements and making a large number of decisions. The elements of design fall into several broad topics, each of which has its own theory, its own research agenda, and its own best practices. That said, there are synergistic effects between these elements, meaning that the overall design process is not just working on each element one at a time, but an iterative feedback process of adjusting each to achieve the desired gestalt.

* Map projections: The foundation of the map is the plane on which it rests (whether paper or screen), but projections are required to flatten the surface of the earth. All projections distort this surface, but the cartographer can be strategic about how and where distortion occurs.
* Generalization: All maps must be drawn at a smaller scale than reality, requiring that the information included on a map be a very small sample of the wealth of information about a place. Generalization is the process of adjusting the level of detail in geographic information to be appropriate for the scale and purpose of a map, through procedures such as selection, simplification, and classification.
* Symbology: Any map visually represents the location and properties of geographic phenomena using map symbols, graphical depictions composed of several visual variables, such as size, shape, color, and pattern.
* Composition: As all of the symbols are brought together, their interactions have major effects on map reading, such as