Clarification of the geophysical definition of a gravity field

Geophysics ◽  
2004 ◽  
Vol 69 (5) ◽  
pp. 1252-1254 ◽  
Author(s):  
Hualin Zeng ◽  
Tianfeng Wan
Keyword(s):  
Gravity Field ◽  
Definition Of

Reply to the Comment on ‘Evaluation of the local value of the Earth gravity field in the context of the new definition of the kilogram’

Metrologia ◽  
2010 ◽  
Vol 47 (3) ◽  
pp. 341-342
Author(s):  
H Baumann ◽  
E E Klingelé ◽  
A L Eichenberger ◽  
B Jeckelmann ◽  
P Richard
Keyword(s):  
Gravity Field ◽  
Earth Gravity Field ◽  
Earth Gravity ◽  
The Earth ◽  
Definition Of ◽  
Local Value

scholarly journals Relativistic effects in geodynamics

1986 ◽  
Vol 114 ◽  
pp. 241-253 ◽  
Author(s):  
C. Boucher
Keyword(s):  
Gravity Field ◽  
Reference Frame ◽  
Relativistic Effects ◽  
Terrestrial Reference Frame ◽  
The Earth ◽  
Lunar Laser ◽  
Time Variations ◽  
Satisfactory Answer ◽  
Definition Of ◽  
Theories Of Gravitation

Geodesy has now reached such an accuracy in both measuring and modelling that time variations of the size, shape and gravity field of the Earth must be basically considered under the name of Geodynamics. The objective is therefore the description of point positions and gravity field functions in a terrestrial reference frame, together with their time variations.For this purpose, relativistic effects must be taken into account in models. Currently viable theories of gravitation such as Einstein's General Relativity can be expressed in the solar system into the parametrized post-newtonian (PPN) formalism. Basic problems such as the motion of a test particle give a satisfactory answer to the relativistic modelling in Geodynamics.The relativistic effects occur in the definition of a terrestrial reference frame and gravity field. They also appear widely into terrestrial (gravimetry, inertial techniques) and space (satellite laser, Lunar laser, VLBI, satellite radioelectric tracking …) measurements.

Tensor Invariants for Gravitational Curvatures

2021 ◽  
Author(s):  
Xiao-Le Deng ◽  
Wen-Bin Shen ◽  
Meng Yang ◽  
Jiangjun Ran
Keyword(s):  
Gravity Field ◽  
Gravity Gradient ◽  
Additional Information ◽  
Tensor Invariants ◽  
Global Gravity ◽  
Potential Applications ◽  
Gravitational Curvatures ◽  
Definition Of ◽  
Elemental Mass ◽  
Derivatives Of

<p>The tensor invariants (or invariants of tensors) for gravity gradient tensors (GGT, the second-order derivatives of the gravitational potential (GP)) have the advantage of not changing with the rotation of the corresponding coordinate system, which were widely applied in the study of gravity field (e.g., recovery of global gravity field, geophysical exploration, and gravity matching for navigation and positioning). With the advent of gravitational curvatures (GC, the third-order derivatives of the GP), the new definition of tensor invariants for gravitational curvatures can be proposed. In this contribution, the general expressions for the principal and main invariants of gravitational curvatures (PIGC and MIGC denoted as I and J systems) are presented. Taking the tesseroid, rectangular prism, sphere, and spherical shell as examples, the detailed expressions for the PIGC and MIGC are derived for these elemental mass bodies. Simulated numerical experiments based on these new expressions are performed compared to other gravity field parameters (e.g., GP, gravity vector (GV), GGT, GC, and tensor invariants for the GGT). Numerical results show that the PIGC and MIGC can provide additional information for the GC. Furthermore, the potential applications for the PIGC and MIGC are discussed both in spatial and spectral domains for the gravity field.</p>

The GGOS Bureau of Products and Standards

2020 ◽  
Author(s):  
Detlef Angermann ◽  
Thomas Gruber ◽  
Michael Gerstl ◽  
Urs Hugentobler ◽  
Laura Sanchez ◽  
...  
Keyword(s):  
Organizational Structure ◽  
Gravity Field ◽  
Working Group ◽  
System Modeling ◽  
Earth System ◽  
Earth System Modeling ◽  
The Earth ◽  
External Stakeholders ◽  
Definition Of

<p>The Bureau of Products and Standards (BPS) supports GGOS in its goal to obtain consistent products describing the geometry, rotation and gravity field of the Earth. A key objective of the BPS is to keep track of adopted geodetic standards and conventions across all IAG components as a fundamental basis for the generation of consistent geometric and gravimetric products. This poster gives an overview about the organizational structure, the objectives and activities of the BPS. In its present structure, the two Committees “Earth System Modeling” and “Essential Geodetic Variables” as well as the newly established Working Group “Towards a consistent set of parameters for the definition of a new GRS” are associated to the BPS. Recently the updated 2<sup>nd</sup> version of the BPS inventory on standards and conventions used for the generation of IAG products has been compiled. Other activities of the Bureau include the integration of geometric and gravimetric observations towards the development of integrated products (e.g., GGRF, IHRF, atmosphere products) in cooperation with the IAG Services and the GGOS Focus Areas, the contribution to the re-writing of the IERS Conventions as Chapter Expert for Chapter 1 “General definitions and numerical standards”, the interaction with external stakeholders regarding standards and conventions (e.g., ISO, IAU, BIPM, CODATA) as well as contributions to the Working Group “Data Sharing and Development of Geodetic Standards” within the UN GGIM Subcommittee on Geodesy.</p>

Selection of operative centrifuge radius to minimize stress error in calculations

1991 ◽  
Vol 28 (1) ◽  
pp. 160-161 ◽  
Author(s):  
Brian Cooke
Keyword(s):  
Stress Distribution ◽  
Key Words ◽  
Gravity Field ◽  
Vertical Stress ◽  
Centrifugal Acceleration ◽  
Centrifuge Model ◽  
Definition Of ◽  
Centre Of Rotation ◽  
Selection Of ◽  
Stress Error

In a centrifuge model, the vertical stress distribution is nonlinear because of the variation of the model's "gravity" field with the centrifuge radius from the top to the bottom of the model. Thus in calculating the centrifugal acceleration, and hence the scale of the model, care must be taken to use the definition of centrifuge radius that minimizes the stress error in the model profile. This paper demonstrates that this optimum radius is measured from the centre of rotation to a point 0.59 times the model height from the bottom of the model. Key words: centrifuge, stress, error.

On: “A Kalman filter approach to susceptibility mapping” by Mark Pilkington and D. J. Crossley (GEOPHYSICS, 52, 655–664, May 1987).

Geophysics ◽  
1988 ◽  
Vol 53 (4) ◽  
pp. 561-561 ◽  
Author(s):  
Nelson C. Steenland
Keyword(s):  
Kalman Filter ◽  
Gravity Field ◽  
Potential Field ◽  
Field Studies ◽  
Salt Dome ◽  
Susceptibility Mapping ◽  
Filter Approach ◽  
Definition Of ◽  
Distribution Of Magnetization ◽  
Single Constant

A single anomaly may be exactly satisfied by a single, constant, magnetization contrast. (“Magnetization” proves to be a much more effective unit to use than “susceptibility.”) These contrasting bodies have discrete boundaries, so the distribution of magnetization shows abrupt discontinuities between adjacent bodies with uniform, single values. Field studies confirm this habit. So to show “apparent susceptibilities” (i.e., Figure 9) as a continuously varying “potential” field may be correct, depending upon the definition of “apparent,” but it is not an accurate nor even helpful exercise. (Try to imagine this process operated over a gravity field in a salt dome province with densities varying continuously within salt which, as is well known, stay remarkably constant at 2.2 g/cc.)

Antarctica crustal model by means of the Bayesian gravity inversion

2020 ◽  
Author(s):  
Martina Capponi ◽  
Daniele Sampietro
Keyword(s):  
Gravity Field ◽  
Gravity Data ◽  
Mass Density ◽  
Geophysical Methods ◽  
Gravity Inversion ◽  
Inversion Algorithm ◽  
Global Gravity ◽  
Uniqueness Of The Solution ◽  
Definition Of ◽  
Regional Gravity

<p>The Antarctica crustal structure is still not completely unveiled due to the presence of thick ice shields all over the continent which prevent direct in situ measurements. In the last decades, various geophysical methods have been used to retrieve information of the upper crust and sediments distribution however there are still regions, especially in central Antarctica, where our knowledge is limited. For these kind of situations, in which the indirect investigation of the subsurface is the only valuable solution, the gravity data are an important source of information. After the recent dedicated satellite missions, like GRACE and GOCE, it has been possible to obtain global gravity field data with spatial resolution and accuracy almost comparable to those of local/regional gravity acquisitions, paving the way to new geophysical applications. The new challenge today is the capability to invert such gravity data on large areas with the aim to obtain a 3D density model of the Earth crust. This is in fact a problem characterized by intrinsic instability and non-uniqueness of the solution that to be solved requires the definition of strong constrains and numerical regularization.</p><p>In this work the authors propose the application of a Bayesian inversion algorithm to the Antarctica continent to infer a model of mass density distribution. The first operation is the definition of an initial geological model in terms of geological horizons and density. These two variables are considered as random variables and, within the iterative procedure based on Markov Chain Monte Carlo methods, they are adjusted in such a way to fit the gravity field on the surface. The test performed show that the method is capable of retrieving an estimated model consistent with the prior information and fitting the gravity observations according to their accuracy.</p>

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