Geographical map

A geographical map is a Représentation of a geographical space. It emphasizes the extent of this space, its relative localization compared to close spaces, as well as the localization of the elements which it contains. The charts are used to represent Phénomène S geographical, i.e. Phénomène S whose space configuration produces Sens.

The applications of this type of representation are as varied as the Navigation, the Town and country planning, the studies demographic or the Communication.

The discipline which has as an aim the creation and the study of the geographical maps is the Cartographie.

Description

Geographical extent

The geographical extent of a chart can be very restricted like very vast. To an extreme the plans of architects are limiting itself to the influence of a building or a whole of buildings; to the other extreme are the world charts representing the whole of the terrestrial sphere.

A geographical map can represent another thing that usual terrestrial surface: seas and oceans, atmosphere, the basement, another planet, a legendary or imaginary world.

A geographical map can also represent a space geographical in the past, the present or the future, or extraterrestrial (Venus or Mars, moon, sky chart.).

Phenomena charted

All Phenomenon which can be localized can be represented on a geographical map.

A classification of the charts can be established by the nature of the phenomena charted. Here examples of the types of charts:

Geological map: levelling basement;
historical chart: last phenomena;
weather chart: weather phenomena;
pedological chart: nature of the grounds;
political map: states and administrative units composing these states;
road map: roads for cars;
topographic Chart: elements of the ground;
tourist chart: tourist infrastructures, remarkable elements of the landscape;
Sea chart: any Bitter object, indication, coast, etc useful for navigation;
cadrastal map: land and buildings;
local plan of town planning (RAINED), plane of occupation of grounds (POS): rules of land use;
Prevention plan of the risks: foreseeable phenomena presenting of the risks.

Localization

The phenomena identified on a geographical map can be localized in two different ways:

by direct positioning. The position of a phenomenon is given by its coordinates. These coordinates can be calculated thanks to graphic tools such as the Compass card, the scale, a squaring, a grid or a framework having the starters of a grid. For example, the modern charts usually present reference marks making it possible to locate the coordinates provided by equipment GPS;
by indirect positioning. The position of a phenomenon can be deduced from the position of other phenomena. For example: a city can be localized by the intersection of a road and a river. This method of localization is facilitated by the presence of benchmarks. The latter can be rivers and cities on charts with small scale or many remarkable points of the landscape for the charts with more large scales.

Representation

A geographical map is a Représentation. It falls under a step of communication. Consequently, graphic conventions used must be adapted to the targeted assistantship and are not universal. They evolved/moved during time and continue to evolve/move according to the culture of the authors or the readers, just as the measuring units (yard, bent, rods, meter, etc). Indeed, according to the countries and the scopes of application the same entities can be represented different manners. Graphic conventions used to represent the phenomena on a chart are described in its Légende.

In spite of the cultural differences evoked above, the following graphic elements can be found on a majority of geographical maps:

of surfaces representing of the phenomena having an extent: a forest, a stretch of water, the zone of impact of a catastrophe for example;
of the lines representing of the phenomena having an one-way space extension: a limit, a section of network, a route for example. On certain charts, these lines can take the appearance of arrows to symbolize a displacement;
of the symbols can represent phenomena such as the Marée S and running S (vectorial arrows) as well as the depth of water, the position of the sand banks, reefs, Phare S, etc (sea charts)
of the symbols representing of the specific phenomena such as a tree isolated on a chart from excursion, the epicentre of a seism or a city on a chart of the World;
of the texts allowing to specify the nature of other graphic elements such as those evoked above: the name of a forest, a point of water, a number of street for example.

Progress of data processing now makes it possible to visualize a chart with a simulation “ 3xD ” of relief, or one or more bottom of layers SIG , or a satellite assembly of images in relief exacerbated (with Google earth, for example, which is a software making it possible to fly over all the terrestrial sphere virtually). Certain software makes it possible to plunge in water or under the ground, since databases ad hoc , describing these zones are available.

Support of the charts

Traditionally the geographical maps are represented on a plane support. One speaks then about a Planisphère or a Mappemonde. However, other supports can be used:

sphere: the use of the term map of the world to speak about a sphere is considered abusive by the French Academy;
relief map: support in relief representing the altitude and the height of the elements constituting the site represented;
dematerialized chart: chart on computer or electronics components embarked (assistance systems with navigation for example);
seen 3D: representation in 3 dimensions, using computer tools, fascinating of account altitude or the height of the phenomena charted.

History

The chart is almost as old as humanity. The oldest known chart goes back to 6200 before J.C to Çatal Hüyük in Turkey.

The first charts were established from day to day progressively terrestrial or maritime explorations and were supplemented following the new discoveries; one thus finds charts old on which portions remained white.

At the end of the 13th century, the Portulan S appeared. They represent the commercial ports, the land-marks (objects fixed and visible being useful of benchmark at sea or on the coast), the islands and the shelters. These charts, ancestors of the navy, used by the sailors do not detail the interior of the grounds.

Until the 18th century, the French language used indifferently the words chart and map which gave the map of the world term as well as the English term map. Thus the administration of the Royaume of Piedmont Sardinia realized at the end of the 18th century, in the Duché of Savoy the first European land register called Sardinian Mappe.

In France, the first topographic chart of the territory produced in a systematic way was drawn up by four generations of cartographers all resulting from the family Cassini at the 18th century. This imposing chart comprised 181 sheets with the 1:86400 which put side by side formed a square of 11 meters with dimensions! This cartographic prowess barrel entièremenent realized by triangulation of 1756 to 1815.

See too

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