Topography

The topography is the art of the measurement then of the representation on a plan or a chart of the forms and details visible on the ground, which they are natural (in particular the Relief) or artificial (like the buildings, the roads, etc). Its objective is to determine the position and the altitude of any point located in a given zone, that it is size of a continent, a country, a field or a body of street.

History

The first traces of measurements of the surface of the ground seem to date from the Egyptians, for the construction of the pyramids and also to position back the limits of cultures after the risings of the Nile. Starting from the Roman Empire, the Arpenteur S were charged to limit the grounds, to establish the buildings and the roads, etc In France, it is with the rebirth that the foregrounds of city are carried out. Claude Chastillon (1559-1616) was the topographer of the king de France Henri IV for which it carried out 544 engravings.

The Lunette is adapted to topography with the}. At that time the essential instrument of the land-surveyor is the small plank (or Goniographe). It is with the techniques evolve/move more, with the invention of the Théodolite and the Tachéomètre which at the same time make it possible to measure the distances and the angles, then in the Années 1950 and 1960 with the invention of the electronic distancemeters. Until there, the measurement of the distances was done using graduated ribbons (known as measuring land chains): these inventions thus constitute a revolution. Since the last decades, the appearance of electronics then data processing gave rise to novel methods of survey and data processing: positioning by satellites (in particular GPS), total stations, laser telemetry, Lasergrammétrie, etc

Use of topography

Topography makes it possible to lead work to the scale of a city or a country by using a planimetric representation (Planimétrie) and altimetric (Altimétrie) identical on the unit of its territory. This work can be constructions of highways, bridges, channels, tunnels, etc

Work of topography is undertaken by geometricians, topographers or geometrician-experts.

From the linguistic point of view, topography is used to describe the space of a place. It belongs to the descriptive typology which gathers several types of descriptions according to the object described.

Charts

The topographic Cartes are a geometrical representation, in general planes, of part of the Earth.

In France one uses the projection of Lambert (see Johann Heinrich Lambert), in order to determine with precision of the points, called geodetic points, which will be known in coordinates. Using this projection one can determine the virtual position of any point located on the French soil. This one will be very close to its real position, about a few decimetres.

The French altimetric system is system IGN 69. Level zero of General Level of France (NGF) is at the Marégraphe of Marseilles.

On each chart, the scale of representation is always present. A squaring indicating the coordinates can also be represented, as well as datum lines representing the Altimétrie.

The charts can make appear only certain elements of the territory in various scales. There exist thus charts of general interest for the private individuals (in particular the charts IGN) and others adapted to the need more specific for professionals. The charts to the 1/25000 present the level lines, the forests, the roads, the cities, etc They are useful for the excursions. The charts adapted to public works are on a building site scale and indicate the site of future constructions and the evolutions in progress.

The French national topographic service is called the national geographical Institute (IGN).

The charts with more large scales which are the plans of the land register are, topographically, of very unequal qualities. In spite of the fastening of all with the system Lambert, there remains imprudent to draw the conclusions from discordances between plan and ground without the council of a professional.

See too

External bonds

  • free Documentations provided by the IGN: to learn how to read a chart, to position, determine its altitude between two known references of the chart, etc
  • Section Topography of the INSA Strasbourg
  • studies in France
  • Site of the IGN (France)
  • presentation of the studies by the academy of Versailles and Lille for their excellent BTS:
    • the BTS geometrician-topographer
    • Bac Pro topographer
    • the technical BEP of the geometrician and topography
  • GéoForm - the gate of the formation into geomatic: Lists of the formations, the establishments, the contacts, bonds useful, remote formation…
  • annuaire.geomatique.info: Directory of Internet sites devoted to geomatic, in particular with topography
  • French Association of Topography the French Association of Topography which publishes review XYZ.
  • GeoRezo, the gate geomatic: Community site of the disciplines composing the géomatique one - Cartography, geographical Information system, Géomarketing, Teledetection, GPS, Topography…
  • Software TopoCad of topography.
  • Topocad By Data-processing synapse. Software for topography, driveways and various services, road studies, calculations of platforms…;
  • Hypergéo: Encyclopedia of geography on line.

Simple: Topography

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