IC SG2

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 JSG 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)