Difference between revisions of "JSG T.35"

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<big>'''JSG 0.22: Definition of next generation terrestrial reference frames'''</big>
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<big>'''JSG T.35: Advanced numerical methods in physical geodesy'''</big>
  
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Chair: ''Christopher Kotsakis (Greece)''<br>
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Chair: ''Robert Čunderlík (Slovakia)''<br>
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Affiliation:''Comm. 1 and GGOS''
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Affiliation:''Commission and GGOS''
  
 
__TOC__
 
__TOC__
  
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===Terms of Reference===
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===Introduction===
  
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A Terrestrial Reference Frame (TRF) is required for measuring the Earth orientation in space, for positioning objects at the Earth’s surface as well as satellites in orbit around the Earth, and for the analysis of geophysical processes and their spatiotemporal variations. TRFs are currently constructed by sets of tri-dimensional coordinates of ground stations, which implicitly realize the three orthogonal axes of the corresponding frame. To account for Earth’s deformations, these coordinates have been commonly modelled as piece-wise linear functions of time which are estimated from space geodetic data under various processing strategies, resulting to the usual type of geodetic frame solutions in terms of station coordinates (at some reference epoch) and constant velocities. Most recently, post-seismic deformation has been added as well in geodetic frame solutions. The requirements of the Earth science community for the accuracy level of such secular TRFs for present-day applications are in the order of 1 mm and 0.1 mm/year, which is not generally achievable at the present time. Improvements in data analysis models, coordinate variation models, optimal estimation procedures and datum definition choices (e.g. NNR conditions) should still be investigated in order to enhance the present positioning accuracy under the “linear” TRF framework.  
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Advanced numerical methods and high performance computing (HPC) facilities provide new opportunities in many applications in geodesy. The goal of this JSG is to apply such numerical methods to solve various problems of physical geodesy, mainly gravity field modelling, processing satellite observations, nonlinear data filtering or others. It focuses on a further development of approaches based on discretization numerical methods like the finite element method (FEM), finite volume method (FVM) and boundary element method (BEM) or the meshless collocation techniques like the method of fundamental solutions (MFS) or singular boundary method (SOR). Such approaches allow gravity field modelling in spatial domain while solving the geodetic boundary-value problems (GBVPs) directly on the discretized Earth’s surface. Their parallel implementations and large-scale parallel computations on clusters with distributed memory allow high-resolution numerical modelling.
  
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Moreover, the consideration of seasonal changes in the station positions due to the effect of geophysical loading signals and other complex tectonic motions has created an additional interest towards the development of “non-linear” TRFs aiming to provide highly accurate coordinates of the quasi-instantaneous positions in a global network. This approach overcomes the limitation of global secular frames which model the average positions over a long time span, yet it creates significant new challenges and open problems that need to be resolved to meet the aforementioned accuracy requirements.
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The JSG is also open to new innovative approaches based for example on the computational fluid dynamics (CFD) techniques, spectral FEM, advection-diffusion equations, or similar approaches of scientific computing. It is also open for researchers dealing with classical approaches of gravity field modelling like the spherical or ellipsoidal harmonics that are using HPC facilities to speed up their processing of enormous amount of input data. This includes large-scale parallel computations on massively parallel architectures as well as heterogeneous parallel computations using graphics processing units (GPUs).
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The above considerations provide the motivation for this JSG whose work will be focused to studying and improving the current approaches for the definition and realization of global TRFs from space geodetic data, in support of Earth mapping and monitoring applications. The principal aim is to identify the major issues causing the current internal/external accuracy limitations in global TRF solutions, and to investigate possible ways to overcome them either in the linear or the non-linear modeling framework.
 
  
 
===Objectives===
 
===Objectives===
  
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* To review and compare from the theoretical point of view the current approaches for the definition and realization of global TRFs, including data reduction strategies and frame estimation methodologies.
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* Design the FEM, BEM and FVM numerical models for solving GBVPs with the oblique derivative boundary conditions.
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* To evaluate the distortion caused by hidden datum information within the unconstrained normal equations (NEQs) to combination solutions by the “minimum constraints” approach, and to develop efficient tools enforcing the appropriate rank deficiency in input NEQs when computing TRF solutions.
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* Develop algorithms for a discretization of the Earth’s surface based on adaptive refinement procedures (the BEM approach).
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* To study the role of the 7/14-parameter Helmert transformation model in handling non-linear (non-secular) global frames, as well as to investigate the frame transformation problem in the presence of modeled seasonal variations in the respective coordinates.
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* Develop algorithms for an optimal construction of 3D unstructured meshes above the Earth’s topography (the FVM or FEM approaches).
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* To study theoretical and numerical aspects of the stacking problem, both at the NEQ level and at the coordinate time-series level, with unknown non-linear seasonal terms when estimating a global frame from space geodetic data.
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* Design numerical models based on MFS or SBM for processing the GOCE gravity gradients in spatial domain.
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* To compare the aforementioned methodology with other alternative approaches in non-linear frame modeling, such as the computation of high-rate time series of global TRFs.
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* Design algorithms for 1D along track filtering of satellite data, e.g., from the GOCE satellite mission.
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* To investigate the modeling choices for the datum definition in global TRFs with particular emphasis on the frame orientation and the different types of no-net-rotation (NNR) conditions.
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* Develop numerical methods for nonlinear diffusion filtering of data on the Earth’s surface based on solutions of the nonlinear heat equations.
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* Investigate innovative approaches based on the computational fluid dynamics (CFD) techniques, spectral FEM or advection-diffusion equations.
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* Apply parallel algorithms using MPI procedures.
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* Apply large-scale parallel computations on clusters with distributed memory.
  
 
===Program of activities===
 
===Program of activities===
  
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* Active participation at major geodetic meetings, promotion of related sessions at international scientific symposia and publication of important findings related to the JSG objectives.
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* Active participation in major geodetic conferences.
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* Proposal for a state-of-art review paper in global frame theory, realization methodologies and open problems, co-authored by the JSG members.
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* Working meetings at international symposia.
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* Organize a related session at the forthcoming Hotine-Marussi Symposium.
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* Organization of a conference session.
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* Launching a web page with emphasis on exchange of research ideas, recent results, updated bibliographic list of references and relevant publications from other disciplines.
 
  
 
===Membership===
 
===Membership===
  
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'' '''Christopher Kotsakis (Greece), chair''' <br /> Zuheir Altamimi (France) <br /> Michael Bevis (USA) <br /> Mathis Bloßfeld (Germany) <br /> David Coulot (France) <br /> Athanasios Dermanis (Greece) <br /> Richard Gross (USA) <br /> Tom Herring (USA) <br /> Michael Schindelegger (Austria) <br /> Manuela Seitz (Germany) <br /> Krzysztof Sośnica (Poland) <br />''
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'' '''Róbert Čunderlík (Slovakia), chair ''' <br /> Petr Holota (Czech Republic) <br /> Michal Kollár (Slovakia) <br /> Marek Macák (Slovakia) <br /> Matej Medľa (Austria) <br /> Karol Mikula (Slovakia) <br /> Zuzana Minarechová (Slovakia) <br /> Otakar Nesvadba (Czech Republic) <br /> Yoshiyuki Tanaka (Japan) <br /> Robert Tenzer (Hong Kong) <br /> Zhi Yin (Germany) <br />''

Latest revision as of 11:55, 10 June 2020

JSG T.35: Advanced numerical methods in physical geodesy

Chair: Robert Čunderlík (Slovakia)
Affiliation:Commission and GGOS

Introduction

Advanced numerical methods and high performance computing (HPC) facilities provide new opportunities in many applications in geodesy. The goal of this JSG is to apply such numerical methods to solve various problems of physical geodesy, mainly gravity field modelling, processing satellite observations, nonlinear data filtering or others. It focuses on a further development of approaches based on discretization numerical methods like the finite element method (FEM), finite volume method (FVM) and boundary element method (BEM) or the meshless collocation techniques like the method of fundamental solutions (MFS) or singular boundary method (SOR). Such approaches allow gravity field modelling in spatial domain while solving the geodetic boundary-value problems (GBVPs) directly on the discretized Earth’s surface. Their parallel implementations and large-scale parallel computations on clusters with distributed memory allow high-resolution numerical modelling.

The JSG is also open to new innovative approaches based for example on the computational fluid dynamics (CFD) techniques, spectral FEM, advection-diffusion equations, or similar approaches of scientific computing. It is also open for researchers dealing with classical approaches of gravity field modelling like the spherical or ellipsoidal harmonics that are using HPC facilities to speed up their processing of enormous amount of input data. This includes large-scale parallel computations on massively parallel architectures as well as heterogeneous parallel computations using graphics processing units (GPUs).

Objectives

  • Design the FEM, BEM and FVM numerical models for solving GBVPs with the oblique derivative boundary conditions.
  • Develop algorithms for a discretization of the Earth’s surface based on adaptive refinement procedures (the BEM approach).
  • Develop algorithms for an optimal construction of 3D unstructured meshes above the Earth’s topography (the FVM or FEM approaches).
  • Design numerical models based on MFS or SBM for processing the GOCE gravity gradients in spatial domain.
  • Design algorithms for 1D along track filtering of satellite data, e.g., from the GOCE satellite mission.
  • Develop numerical methods for nonlinear diffusion filtering of data on the Earth’s surface based on solutions of the nonlinear heat equations.
  • Investigate innovative approaches based on the computational fluid dynamics (CFD) techniques, spectral FEM or advection-diffusion equations.
  • Apply parallel algorithms using MPI procedures.
  • Apply large-scale parallel computations on clusters with distributed memory.

Program of activities

  • Active participation in major geodetic conferences.
  • Working meetings at international symposia.
  • Organization of a conference session.

Membership

Róbert Čunderlík (Slovakia), chair
Petr Holota (Czech Republic)
Michal Kollár (Slovakia)
Marek Macák (Slovakia)
Matej Medľa (Austria)
Karol Mikula (Slovakia)
Zuzana Minarechová (Slovakia)
Otakar Nesvadba (Czech Republic)
Yoshiyuki Tanaka (Japan)
Robert Tenzer (Hong Kong)
Zhi Yin (Germany)

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