Geodesy

The Geodesy ( ancient Greek γῆ gé 'earth' and δαίζειν daízeïn share ') is as defined by Friedrich Robert Helmert and DIN 18709-1 the science of surveying and mapping the earth's surface. This includes the determination of the geometric shape of the Earth ( geoid, terrain ), its gravity field and the orientation of the Earth in space ( Earth's rotation ).

In scientific classification geodesy is associated mainly engineering. This is particularly evident in the technical universities or universities where the geodesy studies is often not associated with the Department of Natural Sciences, but civil engineering. Furthermore, the Geodesy the link between astronomy and geophysics dar.

In mathematics uses the term geodesic for the theoretically shortest distance between two points on curved surfaces - the geodesic line, which corresponds to a great circle on the globe ( geodesic ).

  • 5.1 Important measuring instruments and equipment
  • 5.2 Special and auxiliary equipment
  • 5.3 Historical devices antiquity
  • 5.4 Historical devices of modern times
  • 6.1 Measurement procedure in detail ( in alphabetical order)
  • 6.2 calculation methods and tools
  • 8.1 National
  • 8.2 International

Structure

Geodesy has been divided to about 1930 in two areas:

  • The higher geodesy includes ( as a physical, mathematical and astronomical geodesy) and geodesy, land surveying and astronomical methods.
  • The lower Geodesy ( which requires only flat surfaces computing ) includes simple construction and land surveying; today it is rather called general geodesy, applied geodesy, practical geodesy or surveying piece.

The engineering geodesy used depending on the required accuracy methods in both areas.

By 1950 the aerial measurement established as a separate subject under the name of Photogrammetry - seen since the 1990s, mostly with the remote sensing as a double compartment. As of 1958, the satellite geodesy was born.

The databases of the country or Cadastral developed into geographic information systems (GIS ) and Land Information Systems ( LIS) on.

All of these sub-subjects, however, are usually combined in a higher education program, which also includes the mapping, or at least parts thereof, and a number of other major and minor subjects (eg land tenure ) and to the profession of surveyor leads (see also Geomatics or Geomatikingenieur ). In North America ( and the English literature ), however, differed between Geodesy and Surveying, related little more in the local curriculum. The name corresponds to our word Surveying Surveying.

These academically trained professionals in Europe are active in addition to the above stated objects often in land valuation, construction, IT, cartography, navigation and geospatial information systems, while in the real estate industry - with the exception of the cadastre - prevail rather other configurations. The publicly appointed surveyors ( ÖbVIs ), which in Austria civil engineers, have next to the property being also the right to work in technical areas of geophysics.

Foundations and sub-areas

Geodesy provides with their survey results (eg from cadastral and land surveying, engineering geodesy, photogrammetry and remote sensing ) the basis for numerous other disciplines and activities:

  • In geosciences and natural sciences, for example, in astronomy, physics and oceanography, for geoinformatics and land, for maps (in addition to topographic and thematic maps ) of the geology, geophysics and mapping, as well as for various documentaries about archeology.
  • In the art, especially for civil engineering and architecture, for various civil engineers, civil engineering, the radio and geotechnical engineering and related databases or information systems.

The so-called higher geodesy (mathematical geodesy, physical geodesy and physical geodesy ) deals inter alia with the mathematical figure of the earth, precision reference systems and the determination of the geoid and Earth gravity. To geoid determination, various measuring methods are used: gravimetry, geometric and dynamic methods of satellite geodesy and the Astro geodesy. Knowing the severity is necessary to establish an accurate height system, for example with regard to the North Sea (called NN- ups, see also Amsterdam Level ) or the Adriatic Sea. The official height system in Germany is the German main level network ( DHHN ) embodies.

The geoid (or its gradient, the deflection of the vertical ) is also used for defining and reducing long-range measurements and coordinates on the earth's surface. For triangulation and for longer lines connecting one approaches the sea level by a reference ellipsoid and calculates means of geodetic lines in mathematics ( differential geometry ), navigation, and when clamping easier vault ( geodesic dome ) shall apply. Geoid and gravity field are also important for applied geophysics and the calculation of satellite orbits.

Also the higher geodesy that area of land surveying is to you, in which it comes to regional surveys and their reference systems. These tasks were previously solved terrestrial, now growing with the GPS and other satellite methods.

The so-called lower Geodesy includes the recording of site plans for building design, documentation and creation of digital models for technical projects, the topographic survey of the site, the Cadastral and areas of facility management.

If the ownership of the plots have complicated over time ( by dividing the purchase and sale or inheritance), then a so-called land division is necessary. Your most important tool is the land consolidation, which in Austria melioration. It also serves as the uniform distribution of loads when land for major projects (highways, new lines ) must be applied ( corporate land consolidation ).

With engineering surveying refers to the technical, non-official survey (eg, building alignment, Ingenieurnivellements, establishment of large machines, etc.)

In the performance of geodetic tasks in underground and surface mining is called Markscheidewesen or mountain surveying.

Among the specialty areas of geodesy include the marine geodesy, hydrographic surveying and recording of hydrographic profiles of rivers, the oceanographic altimetry satellite, as well as cooperation in the field of navigation.

A distinction is made between the sub-regions surveying technology as a technical part ( Instrument tuition ) and the non-technical part Surveying as a collective term for the areas of higher and lower geodesy. The land and property being not part of the measurement technique, although German dishes such as the Higher Regional Court Dusseldorf ( OLG) in Decision I-10 W 62/ 06 go against the dominant German universities and universities school of thought of it.

History

Antiquity and Middle Ages

Has its origin in the need to divide the geodesy, land, to define land and property boundaries and to document national borders. Its history goes back to the " hydraulic society" of ancient Egypt, where the profession of surveyors each year, after the flooding of the Nile for a few weeks for most of the country.

Man has dealt with the stars and in particular the shape of the earth has always been considered. First, it was assumed that the earth was a umflossene from the ocean plate. Pythagoras of Samos ( around 500 BC ), although stated that the earth is a sphere, but he could not prove his thesis. This was not until Aristotle ( 350 BC ). He proved the thesis in the following three practical examples:

Of note is the degree measure of the Hellenistic scholar Eratosthenes between Alexandria and Syene was (now Aswan ) to 240 BC. Gave you the circumference of the earth to 252,000 stadia, which came close to the true value, despite the uncertain distance (estimate 5000 stadiums) to about ten percent. The scientist and Alexandrian Library Director estimated the circumference of the earth from the 7.2 degrees different sun.

As in Egypt, the surveying services of the Maya were amazing where geodesy obviously strongly connected with astronomy and calendar calculations.

Even difficult tunnel measurements have been handed down from the first millennium BC, as in the 6th century BC v. the tunnel of Eupalinos on Samos.

Important landmarks of the ancient geodesy were also the first world maps from Greece, the observatories in the Middle East and various measuring instruments to some centers of the eastern Mediterranean. 1023 identified Abu Reyhan Biruni - a polymath of the then Islamic world - with which he invented new methods of measurement of the radius of the earth on the banks of Kabulfluß, then Indus known fairly accurately to 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 driven to its zenith in Arabia in the 11th century, what could also build European scientists as Peuerbach from 1300.

Modern Times

With the dawn of the modern age, the needs of cartography and navigation made ​​for a renewed surge in development, for example in the watch and equipment production of Nuremberg or the measurement and calculation methods of sailors in Portugal. This era was also the discovery of the trigonometric functions (India and Vienna ) and the triangulation ( Snell 1615 ) falls. New instruments like the measuring table ( Praetorius, Nuremberg 1590), the " Pantometrum " of the Jesuit Athanasius Kircher and the telescope / microscope enabled geodesy 's first truly accurate land surveying.

From about 1700, the maps themselves again improved by exact calculation methods (mathematical geodesy) and the beginnings of large-scale physical geodesy, with the determination of the ellipsoidal Earth radii by the French Bouguer and Maupertuis in 1740 experienced its first peak. In order to combine the results of various projects and land surveying better, Roger Joseph Boscovich, Carl Friedrich Gauss developed and other progressive compensatory bill, which zugutekam since 1850 and the establishment of a more specific reference systems and the measurement of space (cosmic geodesy).

For geodesy of the 19th and 20th centuries the most important stages were:

  • The introduction of the meter, the Greenwich zero meridian and from 1950 of a global time system based on wireless technology and Quartz
  • The geoid and gravity measurement and cross-links to Geophysics
  • Increase the measurement accuracy to about one hundred times (dm ⇒ mm per km), including further developments of theodolite and angle measurements, the optical and later electro-optical / electronic distance measurement and finally the EDP contributed
  • From 1960, the increasing use of artificial earth satellites and the immense development of satellite geodesy, which enabled intercontinental measurements for the first time and in 1990 realized the global systems such as GPS
  • From about 1980 radio astronomy by means of interferometry ( VLBI ) as the basis of high-precision reference systems such as ITRF, ETRS89 for global geodesy and geodynamics of the Earth's crust.

Results of geodetic works

  • Fixed-point fields for position, height and gravity
  • Horizontal and vertical coordinates of object points and survey points
  • Dimensions (width, length, height ) of objects
  • Form and shape variations of objects ( planarity, curvature, ...)
  • Orientation of objects ( eg after True North, inclination with respect to vertical)
  • Orientation of objects (distances, alignments, Levelling, ...)
  • Deformation monitoring of objects (see Geodynamics and Engineering Geodesy )
  • Maps and plans
  • Orthophotos
  • Data for Geographic Information Systems
  • Digital terrain models and representations based on it, such as perspective views
  • Visualization of technical objects.

Measuring instruments, devices and equipment

Important measuring instruments and equipment

(Note: The Surveying but rather speaks of instruments, photogrammetry equipment. )

  • Measuring tape and plumb bob (measurement of horizontal distances)
  • Theodolite (measurement of horizontal directions and vertical angles )
  • Tachymeter (measurement of horizontal directions and vertical angles and space routes )
  • Leveling (measurement of height differences)
  • Gravimeter (measurement of the acceleration due to gravity )
  • GNSS (GPS, GLONASS, Beidou or Galileo receiver) (Measurement of spatial paths to more than one satellite )
  • Laser scanner ( automatic measurement of polar elements, two deflection angle and a spatial distance to surfaces in the environment )
  • Measuring chamber ( photogrammetry) ( measurement of reflected radiation - photos, pictures )

Special and auxiliary equipment

  • Distancer, EDM essay
  • Double pentagonal prism ( rectangular prism )
  • Ranging pole or rod escape
  • Combination receiver for GPS and similar methods ( GLONASS, Galileo)
  • Gyrocompass
  • LaserDisto
  • Laser Tracker
  • Staff level
  • Meridional direction gyro
  • Measuring tape, tape measure or measuring tape
  • Prism or reflector
  • Tripod (wood, metal )
  • Marking

Historical devices antiquity

  • Groma
  • Chorobates
  • Dioptra
  • Skiotherikós gnomon

Historical devices of modern times

  • Base bar
  • Bordakreis
  • Bussolentachymeter
  • Alidade
  • Oldham
  • Bar
  • Measuring table
  • Sextant

Measurement and calculation methods

  • Direction and angle measurement
  • Distance measurement ( electro-optical distance measurement), Doppler navigation and inertial navigation
  • Altimetry ( nivellitisch, trigonometric, barometric, altimetry )
  • Photogrammetry (terrestrial, aerial image measurement )
  • Remote Sensing
  • Gravimetry ( gravity measurement ) and gradiometry
  • Satellite Geodesy

Measurement procedures in detail ( in alphabetical order)

  • Stakeout
  • Astronomical localization
  • Digital Image Processing
  • Remote Sensing
  • Free point of choice or free stationing
  • Relative and absolute gravimetry
  • GNSS (Global Navigation Satellite System): Differential GPS (DGPS )
  • Gradiometry
  • Laser Scanning
  • Network measurement
  • Leveling
  • Polar Surveying
  • Traversing (polygon )
  • Photogrammetry
  • Profiling
  • Cutting methods: Straight cut ( cross-bearing ), Resection, forward intersection, Resection ( bow shock)
  • SLR ( Satellite Laser Ranging)
  • SST ( Satellite to Satellite Tracking)
  • Mirrors, scales
  • Triangulation ( geodesy), trilateration
  • VLBI ( Very Long Baseline Interferometry )

Calculation methods and tools

  • Geodetic Computing at PC and programmable calculators geodetic software, surveying software
  • Helmert transformation and spatial methods of coordinate transformation (for example, 7- transformation parameters in GPS systems )
  • Curve fitting and statistical methods
  • Digital cadastre and land register, facility management
  • SAPOS and other regional services for satellite positioning.

Reference Systems

  • Commonly used reference ellipsoids
  • List of important date definitions

Organizations

National

  • Working Committee of the Surveying Authorities of the States of the Federal Republic of Germany - AdV ( Germany )
  • Federal Agency for Cartography and Geodesy - BKG ( Germany )
  • Land survey offices ( Germany )
  • Federal Office of Metrology and Surveying - BEV Vienna ( Austria )
  • Federal Office of Topography - swisstopo ( Switzerland )
  • DVW - Society for Geodesy, Geoinformation and Land Management eV - DVW ( Germany )
  • German Association of Surveyors - VDV ( Germany )
  • Alliance of Publicly Appointed Surveyors - BDVI ( Germany )
  • German Geodetic Research Institute
  • German Geodetic Commission
  • Swiss Geodetic Commission - SGC - Swiss Geodetic Commission

Internationally

  • International Federation of Géomètres ( FIG)
  • International Association of Geodesy (IAG )
  • International Geodetic Student Organisation ( IGSO )

Significant geodesics

Gaia (mythology) Plane (geometry) Geotechnics Amsterdam Ordnance Datum Vertical deflection Controlled-access highway Boundary (real estate) Grade measurement Maya civilization Arabian Peninsula Plane table Pierre Bouguer Metre Convention Coordinate system Tacheometer Groma surveying subtense bar Repeating circle Helmert-Transformation Karl Ledersteger Integrated Authority File
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