What instruments are used in the survey

geodesy

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The geodesy (ancient Greek. Geo (γη) = Earth, däsie (δαιζω) = I share) is according to the classic definition of F. R. Helmert "Science of the measurement and mapping of the earth's surface". This includes the determination of the geometric figure of the earth (geoid, terrain), its gravitational field and the orientation of the earth in space (earth rotation). According to DIN 18709-1, it is the science of the measurement and mapping of the earth's surface (including the determination of the earth's gravity field and the sea floor).

In scientific systematics, geodesy is on the one hand the link between astronomy and geophysics, on the other hand many of its processes can be assigned to the engineering sciences. This is particularly clear at technical universities, where geodesy is often not assigned to the natural sciences but to civil engineering.

In mathematics, the term "geodetic" is used for the theoretically shortest connection between two points on curved surfaces - the Geodetic linewhich corresponds to a great circle (orthodrome) on the globe.

Lithographic plates in the archive of the Bavarian Surveying Office

[Edit] Outline of geodesy

Until about 1930, geodesy was divided into two areas:

The Engineering geodesy uses methods from both areas depending on the required accuracy.

Around 1950, aerial photo measurement established itself as a separate subject under the name Photogrammetry - since the 1990s mostly with the Remote sensing seen as a double subject.

From 1958 the Satellite geodesy.

The databases of the state and cadastral surveying developed into geographic information systems (GIS) or land information systems (LIS).

However, all of these sub-subjects are mostly in one A university course that also includes cartography or at least parts of it as well as a number of other major and minor subjects (e.g. land management) and leads to the occupation of surveying engineer (see also geomatics or geomatics engineer). In North America (and English technical literature), however, between Geodesy and Surveying differentiated, which are hardly related in the curricula there. The designation Surveying corresponds to our word measurement.

These professionals, who are academically trained in Europe, are in addition to the o. Tasks often also involved in property valuation, construction, IT, cartography, navigation and spatial information systems, while in the real estate industry - with the exception of the cadastre - other training courses predominate. Civil engineers who work geodetically (Austrian, in Germany called ÖbVI) have the right to work in technical areas of geophysics in addition to real estate management.

[Edit] Brief history of geodesy

Geodesy has its origins in the need to divide up land, define property and property boundaries and document national boundaries. The history of geodesy goes back to ancient Egypt, where the occupation of geodesy became the most important in the country for a few weeks every year after the Nile flood.

The Hellenistic scholar Eratosthenes' measurement of degrees between Alexandria and Syene (today's Aswan) around 240 BC was remarkable. It gave the earth's circumference to 252,000 stadia, which came close to the true value despite the uncertain distance (estimate 5,000 stadia) to about 10 percent. The scientist and Alexandrian library director estimated the circumference of the earth from the 7.2 ° difference in the position of the sun.

As in Egypt, the surveying achievements of the Maya were astonishing, where geodesy was evidently strongly related to astronomy and calendar calculations.

Difficult tunnel measurements are also from the 1st millennium BC. Chr. Handed down, such as an almost 1 km long water tunnel in Israel.

Important milestones of ancient geodesy were also the first world maps from Greece, the observatories in the Middle East and various measuring instruments at some centers of the eastern Mediterranean. In 1023, Abu Reyhan Biruni - a polymath of the Islamic world at the time - determined the radius of the globe on the banks of the Kabul River, then called the Indus, with a new measuring method he had invented to be almost exactly 6339.6 km. (The radius at the equator of the earth is actually 6378.1 kilometers.) At that time, the construction of sundials and astrolabes was pushed to its peak in Arabia in the 11th century, something that European scientists like Peuerbach could build on from 1300 onwards.

With the dawn of the modern era, the needs of cartography and navigation provided a renewed boost in development, for example in clock and device production in Nuremberg or the measurement and calculation methods used by Portuguese seafarers. The discovery of the angular functions (India and Vienna) and triangulation (Snellius around 1615) also fell into this epoch. New measuring instruments such as the measuring table (Prätorius, Nuremberg 1590), the "pantometrum" of the Jesuit A.Kircher and the telescope / microscope enabled geodesy to carry out the first really precise land surveys.

From around 1700, the maps improved again through exact calculation methods (mathematical geodesy) and the beginning of large-scale earth measurements, which reached its first high point in 1740 with the determination of the ellipsoidal earth radii by the French Bouguer and Maupertuis. In order to be able to combine the results of various projects and national surveys better, Roger Joseph Boscovich, Carl Friedrich Gauß and others gradually developed the equalization calculation, which since around 1850 has also benefited the establishment of precise reference systems and the measurement of space (cosmic geodesy).

The most important stations for geodesy in the 19th and 20th centuries were:

[Edit] Basics and sub-areas

With its survey results (e.g. from cadastral and national surveying, engineering geodesy, photogrammetry and remote sensing), geodesy provides the basis for numerous other specialist areas and activities:

  • in the field of geo- and natural sciences z. B. for astronomy, physics and oceanography, for geoinformatics and cadastre, for maps (in addition to topographical and thematic maps) of geology, geophysics and cartography, as well as for a wide variety of documentation, such as archeology.
  • in technology, especially for construction and architecture, for various civil engineers, civil engineering, radio and geotechnical engineering and related databases or information systems.

The so-called higher geodesy (mathematical geodesy, earth measurement and physical geodesy) deals, among other things, with the mathematical figure of the earth, precise reference systems and the determination of geoid and earth's gravitational field. Various measurement methods are used to determine geoid: gravimetry, geometric and dynamic methods of satellite geodesy and astrogeodesy. Knowing the gravity is necessary to establish an exact height system - e.g. B. with regard to the North Sea (so-called NN heights, see also Amsterdam level) or the Adriatic Sea. The official height system in Germany is embodied in the German Main Height Network (DHHN).

The geoid (or its gradient, the deviation from the perpendicular) also serves to define and reduce large-scale measurements and coordinates on the earth's surface. For triangulation and for longer connecting lines, the sea level is approximated using a reference ellipsoid and calculated using geodetic lines, which are also used in mathematics (differential geometry), navigation and when spanning light vaults (geodetic dome). Geoid and gravitational field are also important for applied geophysics and for calculating satellite orbits.

Also the Higher Geodesy is to be assigned to the area of ​​national surveying that deals with regional surveys and their reference systems. These tasks were previously solved terrestrially, but now increasingly with GPS and other satellite methods.

The so-called lower geodesy includes the recording of site plans for construction planning, documentation and creation of digital models for technical projects, the topographical recording of the site, the cadastral survey and areas of facility management.

If the ownership structure of the land has become more complicated over the course of time (through division when buying and selling or inheriting), so-called zoning becomes necessary. Their most important instrument is land consolidation, known in Austria as amelioration. It also serves to evenly distribute loads when areas have to be raised for large projects (motorways, new construction routes) (company land consolidation).

Engineering surveying is the name given to them technical, non-official surveying (e.g. building outlines, engineering leveling, setting up large machines, etc.)

When performing geodetic tasks in underground and surface mining, one speaks of mine separation or mountain surveying.

The special fields of geodesy also include marine geodesy, sea surveying and recording of hydrographic profiles of rivers, oceanographic altimetry with satellites and cooperation in the field of navigation.

[Edit] Geodetic reference systems

This article or section needs to be revised. Details are given on the talk page. Please help to improve it and then remove this mark.

(see also: Frequently used reference ellipsoids or list of important date definitions)

[Edit] Measurement and calculation methods in geodesy

[Edit] Measurement method in detail (alphabetically)

[Edit] Calculation methods and calculation tools of geodesy

[Edit] Measuring instruments, devices and equipment

[Edit] Important instruments and devices

(Note: Surveyors tend to speak of instruments, but photogrammetry of devices.)

[Edit] Special and auxiliary equipment

[Edit] Historical devices of antiquity

[Edit] Historic devices of the modern age

[Edit] Results of geodetic work

[Edit] Organizations

[Edit] Important geodesics

see article Geodesy

[Edit] Literature

  • Karl Ledersteger: Astronomical and physical geodesy. 10th edition. Metzler, Stuttgart 1969 (Handbook of Surveying 5)
  • Hans-Gert Kahle: Introduction to higher geodesy. 2nd (extended) edition. Verlag der Fachvereine, Zurich 1988, ISBN 3-7281-1655-6
  • Wolfgang Torge: Geodesy. 2nd Edition. De Gruyter, Berlin 2003, ISBN 3-11-017545-2
  • Bertold Witte, Hubert Schmidt: Surveying and the basics of statistics for the construction industry. 5th edition. Wichmann, Heidelberg 2004, ISBN 3-87907-418-6
  • Bettina Schütze, Andreas Engler, Harald Weber: Textbook surveying basic knowledge. Weber, Dresden 2001, ISBN 3-936203-00-8
  • Walther Welsch, Otto Heunecke, Heiner Kuhlmann: Evaluation of geodetic monitoring measurements. In: M. Möser, G. Müller, H. Schlemmer, H. Werner (Eds.): Handbook of engineering geodesy. Wichmann, Heidelberg 2000, ISBN 3-87907-295-7
  • Vitalis Pantenburg: The portrait of the earth. History of cartography. Franckh, Stuttgart 1970, ISBN 3-440-00266-7
  • European Commission (ed.): Spatial Reference Systems for Europe. European Commission, 2000 (EUR 19575, PDF, 13.7 MB - European coordinate reference systems as a geodetic contribution to spatial data infrastructure)
  • Walter Grossmann: Geodetic calculations and images in the national survey. 3. Edition. Wittwer, Stuttgart 1976

[Edit] Web links

 Wiktionary: geodesy - Explanations of meanings, word origins, synonyms, translations and grammar