Results of the IfE absolute gravity campaigns in 2004

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Superiority of Scintrex CG relative gravimeters
Ludger Timmen
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Motivation

• Find the optimal sensor or optimal sensor mix for
  specific tasks!
• Many gravimetric applications require only
  absolute scale surveys
• eccentre measurements
• gravity gradients
• densification of national networks
• dense point data to improve regional geoids
• monitoring of gravity changes (geodynamics)
• If the absolute level for gravity differences is
  not required,
• relative gravimetry can be applied, evtl.
  supplementary to absolute gravimetry.
• The big question
• How accurate is relative gravimetry with respect
  to its
• absolute scale?

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Table 1 MAXIMUM AND MEAN AMPLITUDE OF THE
PERIODIC CALIBRATION TERMS AS DERIVED FOR 21
LACOSTE-ROMBERG MODELL G GRAVIMETERS IN THE
GRAVIMETER CALIBRATION SYSTEM HANNOVER
Main features of SCG

• non-astatised quartz spring system,
• capacitive displacement transducer with feedback
  system (0.2 nm resolution),
• vacuum chamber for gravity sensing system,
• no micrometer screw, no gearbox, no mechanical
  feedthrough.

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Investigations time stability of
calibration, Gravity range dependency.
Fig. 3. - The station distribution of the
gravimeter calibration system Hannover
(Cuxhaven-Harz mountains, 3000 µm/s2, 90 µm/s2
interval), e.g. TORGE, 1989.
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The investigation of the Scintrex Autograv CG-3M
no. 4492 yielded the following results    Over
2.5 years of surveys, the calibration was stable
at least in the order of 110-4. No instability
could be proven.    Within a total range of
almost 0.015 m/s², no gravity range dependence
has been found.    For gravity ties with short
distances (local and microgravimetric nets), the
connection can be determined with an accuracy of
10 nm/s². Observation and calibration
uncertainties are considered.