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Topics on Gravity Field

Deutsches, kombiniertes Quasigeoid (GCG05)
Deutsches, kombiniertes Quasigeoid (GCG05)

The calculation and determination of the shape of the Earth is beside others, one of the main research fields of the Institute for Geodesy (IfE). Our Institute has unique facilities in Germany available  to determine the Shape of the Geoid with teresstrial instruments. Two of these facilities are the absolute gravimeter FG5-220 as well as the real time, transportable zenith camera TZK2-D. These fields of research are represented by the terrestrial gravimetry and the geodetic astronomy. At both methods  horizontal components of the deflexion of the vertical are measured to determine the shape of the Earth's Gravity Field. Both fields of research deal with terrestrial methods in contrast to the satellite missions, which deal with remote sensing methods.

The terrestrial determination of the Earth's Gravity Field is in close contact to the research field High Resolution Gravity Modelling. From 1990 to 2003 out Institute acts as a computing center of the IAG (International Association of Geodesy) geoid sub-commission for Europe. The "European Gravity and Geoid Project (EGGP)" proved that significant accuracy improvements are possible in central Europe through the use of updated gravity field data sets and GRACE geopotential models. Moreover, the gravity field data sets from the European Geoid Project are also utilized in connection with the validation and calibration of the satellite gravity field missions CHAMP, GRACE und GOCE.

High Resolution Gravity Field Modelling

Geiod Model of the Earth. Potatao or Balll?
Geiod Model of the Earth. Potatao or Balll?

The Institute of Geodesy (Institut für Erdmessung, IfE) at LUH (Leibniz Universität Hannover) plays a leading role in terrestrial gravimetry and regional geoid determination and its combination with satellite data (e.g. from GRACE). On the following web pages detailled information dealing with high resolution gravity field modelling can be find.

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Terrestial Gravimetry

Absolutgravimeter FG5X-220, Institute for Geodesy (IfE).
Absolutgravimeter FG5X-220, Institute for Geodesy (IfE).

The perception of "gravimetry" is a mixture of two clear defined words: from the latin word gravitas = gravity and the greek word τ μέτρον = dimension/measurement and means "gravity measurement".

Gravimetry is the metrology of the gravity measurement or in other words the metrology of the measurement of the acceleration of gravity on the Earth's surface. By means of gravity measurements the Earth Gravity Filed is determined by terrestrial methods. 

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Geodetic Astronomy | TZK2-D

Transportable Zenith camera during measurements in the Alps.
Transportable Zenith camera during measurements in the Alps.

On the basis of the convential transportable zenith camera TZK2, a new technology was developed by means of CCD technology at the Institute for Geodesy, which allows a real-time and high-precision as well as nearly complete automated application with the name TZK2-D (transportable zenith camera 2 - digital). The astronomic coordinates are measured by a CCD photo of the stars nearby zenith with an precision of approx. 0.1 arcsec. In combination with a GNSS receiver, it is possible to determine the astrogeodetic vertical deflection components for high-resolution gravity field determination on local and regional scales.

 

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