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Physics of the Globe
Published in Aurèle Parriaux, Geology, 2018
The gravimeter is an instrument for measuring gravitational differences between a reference station and points measured in the field. The principle of the gravimeter is very simple (Fig. 4.41). A mass is suspended from the housing of the gravimeter by a spring that has a small drift over time. A mirror is placed on both the fixed solid arm of the housing and the suspended mass. At the reference station, the length of the spring is set using a micrometric screw so that the luminous bundle reflected by the mirror arrives right in the middle of the ocular. When the instrument is moved to a point in the field, a gravitational difference requires a modification of the spring length. The luminous bundle no longer reaches the ocular. The initial position of the bundle is re-established by moving the micrometric screw. The adjustment of the micrometric screw is converted to the gravity difference.
Physics of the Globe
Published in Aurèle Parriaux, Geology, 2018
The gravimeter is an instrument for measuring gravitational differences between a reference station and points measured in the field. The principle of the gravimeter is very simple (Fig. 4.41). A mass is suspended from the housing of the gravimeter by a spring that has a small drift over time. A mirror is placed on both the fixed solid arm of the housing and the suspended mass. At the reference station, the length of the spring is set using a micrometric screw so that the luminous bundle reflected by the mirror arrives right in the middle of the ocular. When the instrument is moved to a point in the field, a gravitational difference requires a modification of the spring length. The luminous bundle no longer reaches the ocular. The initial position of the bundle is re-established by moving the micrometric screw. The adjustment of the micrometric screw is converted to the gravity difference.
Petroleum Geophysical Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
A variety of commercial gravimeters are available. The principle of working of the gravity determination apparatus is either of a ‘spring elongation’ or ‘pendulum oscillation time period’ under the influence of gravitational force. Again, spring elongations (extension) or the time period of pendulum oscillation is not measured in absolute terms. Only the initial and final meter readings (number) are recorded on an already calibrated instrument. Gravity variation or anomaly is estimated with the help of elongation or time period recorded by the instrument. Two types of gravimeters, based on the above-mentioned principle, are the spring elongation balance and the pendulum torsion instrument. A third type of gravimeter is based on the combination of these two features.
Workplace exposure to particulate matter, bio-accessible, and non-soluble metal compounds during hot work processes
Published in Journal of Occupational and Environmental Hygiene, 2019
Balázs Berlinger, Ulf Skogen, Conny Meijer, Yngvar Thomassen
The collected aerosol particulate mass on the filters was determined gravimetrically with a Sartorius Micro model MC5 balance with six decimal places (Sartorius AG, Göttingen, Germany) in a weighing room dedicated to low filter mass measurements, under controlled relative humidity (40 ± 2%) and temperature (20 ± 1°C) conditions. The balance was calibrated daily. Accuracy and precision of gravimetry were assessed by weighing certified reference masses (19.989 ± 0.030 and 49.953 ± 0.040 mg). The mass detection limits (DLs) were calculated as three times standard deviation of all field blanks and were 0.01 mg for all the filters used in this study.
Geoid determination using band limited airborne horizontal gravimetric data
Published in Journal of Spatial Science, 2022
Kailiang Deng, Guobin Chang, Motao Huang, Huaien Zeng, Xin Chen
The Geoid or Quasi-Geoid is the reference surface of the height system in spatial science. Specifically a geoid model with sufficiently high resolution and precision makes efficient GNSS-leveling possible (Featherstone 2008, Trojanowicz 2015). Determination of the geoid is one of the fundamental tasks of geodetic science and practice. Recently, benefiting from the increased precision of both differential GNSS positioning technology and gravimetry sensor technology, airborne vector gravimetry has emerged as a major progress in the geodetic community, compared to conventional scalar gravimetry Sander and Ferguson 2010, Cai et al. 2013). Vector gravimetry model equations were stated and their error models were derived in Schwarz and Li (1997). The repeated-line precision of results with the AIRGrav airborne gravity system can reach as high as 0.34 and 0.28mGal for the north and east components, respectively (Sander and Ferguson 2010). Results with a strapdown system named SGA-WZ are 1.23 and 1.80mGal, respectively (Cai et al. 2013). These experimental results show that it is now practically possible that incorporating horizontal components of gravity in the determination of the geoid could achieve relatively high resolution and accuracy. However, in recent years, theoretical and practical studies concerning geoid determination were mainly focused on using the vertical component as the only data source (Novák and Heck 2002, Novák et al. 2003). Similar to astronomical levelling theory, a sub-decimeter geoid can be obtained by integrating the horizontal components of vector airborne gravimetry data along the surveying profiles (Jekeli and Kwon 2002, Serpas and Jekeli 2005). However, only a relative geoid can be obtained using this method, which apparently limits its applicability. As a result, determining the absolute geoid using horizontal components of vector airborne gravimetry data, as the main topic of this study, is of significant theoretical and practical importance.