IC SG2

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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 pur-pose of WHS realization.
  • To define a role of a conventional model of the Earth’s gravity field (EGM) to be used for WHS realization in-cluding its scale parameters.
  • To study relations between an adopted conventional EGM and parameters of a geocentric reference ellipsoid of revolution approximating a time invariant equipoten-tial 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 investiga-tions 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 con-tinuation of gravity field parameters including space-borne 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 con-tinuation 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 SG web page. Monitoring activities of SG members and external individuals related to SG. Compiling bibliography in the area of SG 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)