Difference between revisions of "IC SG2"

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<big>'''JSG 0.11: Multiresolutional aspects of potential field theory'''</big>
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<big>'''JSG 0.2: Gravity field modelling in support of world height system realization'''</big>
  
Chair:''Dimitrios Tsoulis (Greece)''<br>
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Chair:''P. Novák (Czech Republic)''<br>
Affiliation:''Comm. 2, 3 and GGOS''
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Affiliation:''Comm. 2, 1 and GGOS''
  
 
__TOC__
 
__TOC__
 
 
===Introduction===
 
===Introduction===
  
The mathematical description and numerical computation of the gravity signal of finite distributions play a central role in gravity field modelling and interpretation. Thereby, the study of the field induced by ideal geometrical bodies, such as the cylinder, the rectangular prism or the generally shaped polyhedron, is of special importance both as fundamental case studies but also in the frame of terrain correction computations over finite geographical regions.
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Description of the Earth’s gravity field still remains a major research topic in geodesy. The main goal is to provide reliable global models covering all spatially-temporal frequencies of its scalar parameterization through the gravity potential. Detailed and accurate gravity field models are required for proper positioning and orientation of geodetic sensors (data geo-referencing). Geometric properties of the gravity field are then studied including those of its equipotential surfaces and their respective surface normals, since they play a fundamental role in definition and realization of geodetic reference systems. Gravity field models will be applied for definition and realization of a vertical reference system (currently under construction) that will support studies of the Earth system.
Analytical and numerical tools have been developed for the potential function and its derivatives up to second order for the most familiar ideal bodies, which are widely used in gravity related studies. Also, an abundance of implementations have been proposed for computing these quantities over grids of computational points, elaborating data from digital terrain or crustal databases.
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This study group is an entity of the Inter-Commission Committee on Theory. It is affiliated to Commissions 1 (Reference Frames) and 2 (Gravity Field); its close co-operation with GGOS Theme 1 “Unified Global Height System” is anticipated. It aims at bringing together scientists concerned namely with theoretical aspects in the areas of interest specified below.
Scope of the Study Group is to investigate the possibilities of applying wavelet and multiscale analysis methods to compute the gravitational effect of known density distributions. Starting from the cases of ideal bodies and moving towards applications involving DTM data, or hidden structures in the Earth's interior, it will be attempted to derive explicit approaches for the individual existing analytical, numerical or combined (hybrid) methodologies. In this process, the mathematical consequences of expressing in the wavelet representation standard tools of potential theory, such as the Gauss or Green theorem, involved for example in the analytical derivations of the polyhedral gravity signal, will be addressed. Finally, a linkage to the coefficients obtained from the numerical approaches but also to the potential coefficients of currently available Earth gravity models will also be envisaged.
 
  
 
===Objectives===
 
===Objectives===
  
* Bibliographical survey and identification of multiresolutional techniques for expressing the gravity field signal of finite distributions.
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* Considering different types and large amounts of gravity-related data available today, large variety of gravity field models and the ongoing IAG project of realizing a world height system (WHS), this study group shall focuses on theoretical aspects related to the following (non-exhaustive to WHS) list of problems:
* Case studies for different geometrical finite shapes.
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* To study available gravity field models in terms of their available resolution, accuracy and stability for the purpose of WHS realization.
* Comparison and assessment against existing analytical, numerical and hybrid solutions.
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* To define a role of a conventional model of the Earth’s gravity field (EGM) to be used for WHS realization including its scale parameters.
* Computations over finite regions in the frame of classical terrain correction computations.
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* To study relations between an adopted conventional EGM and parameters of a geocentric reference ellipsoid of revolution approximating a time invariant equipotential surface of the adopted EGM aligned to reduced observables of mean sea level.
* Band limited validation against available Earth gravity models.
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* To study theoretical aspects of various methods proposed for WHS definition and realization including investigations on tidal system effects.
 +
To investigate combination of heterogeneous gravity field observables by using spatial inversion, spherical radial functions, collocation, wavelets, etc. and by taking into account their sampling geometry, spectral and stochastic properties.
 +
* To investigate methods of gravity field modelling based on combination of global gravitational models, ground and airborne gravity, GNSS/levelling height differences, altimetry data, deflections of the vertical, etc.
 +
* To study stable, accurate and efficient methods for continuation of gravity field parameters including spaceborne observables of type GRACE and GOCE.
 +
* To advance theory and methods for solving various initial and boundary value problems (I/BVP) in geodesy.
 +
* To study methods for gravity potential estimation based on its measured directional derivatives (gravity, gravity gradients) by exploiting advantages of simultaneous continuation and inversion of observations.
 +
* To investigate requirements for gravity data (stochastic properties, spatially-temporal sampling, spectral content etc.) in terms of their specific geodetic applications.
  
 
===Program of Activities===
 
===Program of Activities===
  
* Active participation at major geodetic meetings.
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Active participation at major geodetic conferences and meetings.
* Organize a session at the forthcoming Hotine-Marussi Symposium.
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Organizing a session at the Hotine-Marussi Symposium 2013.
* Compile a bibliography with key publications both on theory and applied case studies.
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Co-operation with affiliated IAG Commissions and GGOS.
* Collaborate with other working groups and affiliated IAG Commissions.
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Electronic exchange of ideas and thoughts through a JSG web page.
 +
Monitoring activities of SG members and external individuals related to JSG.
 +
Compiling bibliography in the area of JSG interest.
  
 
===Members===
 
===Members===
  
'' '''Dimitrios Tsoulis (Greece), chair''' <br />Katrin Bentel (USA) <br /> Maria Grazia D'Urso (Italy) <br /> Christian Gerlach (Germany) <br /> Wolfgang Keller (Germany) <br /> Christopher Kotsakis (Greece) <br /> Michael Kuhn (Australia) <br /> Pavel Novák (Czech Republic) <br /> Konstantinos Patlakis (Greece) <br /> Clément Roussel (France) <br /> Michael Sideris (Canada) <br />Jérôme Verdun (France) <br /> Christopher Jekeli (USA) <br /> Frederik Simons (USA) <br /> Nico Sneeuw (Germany)''
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'' '''Pavel Novák (Czech Republic), chair'''<br />Hussein Abd-Elmotaal (Egypt)<br />Robert Čunderlík (Slovakia)<br />Heiner Denker (Germany)<br />Will Featherstone (Australia)<br />René Forsberg (Denmark)<br />Bernhard Heck (Germany)<br />Jianliang Huang (Canada)<br />Christopher Jekeli (USA)<br />Dan Roman (USA)<br />Fernando Sansò (Italy)<br />Michael G Sideris (Canada)<br />Lars Sjöberg (Sweden)<br /> Robert Tenzer (New Zealand)<br />Yan-Ming Wang (USA)<br />''

Revision as of 10:07, 2 July 2012

JSG 0.2: Gravity field modelling in support of world height system realization

Chair:P. Novák (Czech Republic)
Affiliation:Comm. 2, 1 and GGOS

Introduction

Description of the Earth’s gravity field still remains a major research topic in geodesy. The main goal is to provide reliable global models covering all spatially-temporal frequencies of its scalar parameterization through the gravity potential. Detailed and accurate gravity field models are required for proper positioning and orientation of geodetic sensors (data geo-referencing). Geometric properties of the gravity field are then studied including those of its equipotential surfaces and their respective surface normals, since they play a fundamental role in definition and realization of geodetic reference systems. Gravity field models will be applied for definition and realization of a vertical reference system (currently under construction) that will support studies of the Earth system. This study group is an entity of the Inter-Commission Committee on Theory. It is affiliated to Commissions 1 (Reference Frames) and 2 (Gravity Field); its close co-operation with GGOS Theme 1 “Unified Global Height System” is anticipated. It aims at bringing together scientists concerned namely with theoretical aspects in the areas of interest specified below.

Objectives

  • Considering different types and large amounts of gravity-related data available today, large variety of gravity field models and the ongoing IAG project of realizing a world height system (WHS), this study group shall focuses on theoretical aspects related to the following (non-exhaustive to WHS) list of problems:
  • To study available gravity field models in terms of their available resolution, accuracy and stability for the purpose of WHS realization.
  • To define a role of a conventional model of the Earth’s gravity field (EGM) to be used for WHS realization including its scale parameters.
  • To study relations between an adopted conventional EGM and parameters of a geocentric reference ellipsoid of revolution approximating a time invariant equipotential surface of the adopted EGM aligned to reduced observables of mean sea level.
  • To study theoretical aspects of various methods proposed for WHS definition and realization including investigations on tidal system effects.

To investigate combination of heterogeneous gravity field observables by using spatial inversion, spherical radial functions, collocation, wavelets, etc. and by taking into account their sampling geometry, spectral and stochastic properties.

  • To investigate methods of gravity field modelling based on combination of global gravitational models, ground and airborne gravity, GNSS/levelling height differences, altimetry data, deflections of the vertical, etc.
  • To study stable, accurate and efficient methods for continuation of gravity field parameters including spaceborne observables of type GRACE and GOCE.
  • To advance theory and methods for solving various initial and boundary value problems (I/BVP) in geodesy.
  • To study methods for gravity potential estimation based on its measured directional derivatives (gravity, gravity gradients) by exploiting advantages of simultaneous continuation and inversion of observations.
  • To investigate requirements for gravity data (stochastic properties, spatially-temporal sampling, spectral content etc.) in terms of their specific geodetic applications.

Program of Activities

Active participation at major geodetic conferences and meetings. Organizing a session at the Hotine-Marussi Symposium 2013. Co-operation with affiliated IAG Commissions and GGOS. Electronic exchange of ideas and thoughts through a JSG web page. Monitoring activities of SG members and external individuals related to JSG. Compiling bibliography in the area of JSG interest.

Members

Pavel Novák (Czech Republic), chair
Hussein Abd-Elmotaal (Egypt)
Robert Čunderlík (Slovakia)
Heiner Denker (Germany)
Will Featherstone (Australia)
René Forsberg (Denmark)
Bernhard Heck (Germany)
Jianliang Huang (Canada)
Christopher Jekeli (USA)
Dan Roman (USA)
Fernando Sansò (Italy)
Michael G Sideris (Canada)
Lars Sjöberg (Sweden)
Robert Tenzer (New Zealand)
Yan-Ming Wang (USA)