Difference between revisions of "IC SG3"

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<big>'''Configuration analysis of Earth oriented space techniques'''</big>
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<big>'''JSG 0.12: Advanced computational methods for recovery of high-resolution gravity field models'''</big>
  
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Chair: ''F. Seitz (Germany)''<br>
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Chairs: ''Robert Čunderlík (Slovakia)''<br>
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Affiliation: ''Comm. 3, 2, 1''
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Affiliation: ''Comm. 2 and GGOS''
  
 
__TOC__
 
__TOC__
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===Introduction===
 
===Introduction===
  
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Activities of the study group are focussed on modern methods of Earth observation from space. Today a multitude of simultaneously operating satellite systems with different objectives are available. They offer a broad spectrum of information on global and regional-scale processes within and/or between individual components of the Earth system in different temporal resolutions.
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Efficient numerical methods and HPC (high performance computing) facilities provide new opportunities in many applications in geodesy. The goal of the JSG is to apply numerical methods and/or HPC techniques mostly for gravity field modelling and nonlinear filtering of various geodetic data. The discretization numerical methods like the finite element method (FEM), finite volume method (FVM) and boundary element method (BEM) or the meshless methods like the method of fundamental solutions (MFS) or singular boundary method (SOR) can be efficiently used to solve the geodetic boundary value problems and nonlinear diffusion filtering, or to process e.g. the GOCE observations. Their parallel implementations and large-scale parallel computations on clusters with distributed memory using the MPI (Message Passing Interface) standards allows to solve such problems in spatial domains while obtaining high-resolution numerical solutions.  
  
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The general objective of this study group is the development of strategies how complementary and redundant information from heterogeneous observation types can be combined and analysed with respect to physical processes in the Earth system.
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Our JSG is also open for researchers dealing with the classical approaches of gravity field modelling (e.g. the spherical or ellipsoidal harmonics) that are using high performance computing 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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Most of the measurement techniques are restricted to the observation of integral effects of a multitude of underlying geophysical processes. It shall be investigated in which way the combination of heterogeneous data sets allows for the separation of processes and the identification of individual contributors.
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Applications of the aforementioned numerical methods for gravity field modelling involve a detailed discretization of the real Earth’s surface considering its topography. It naturally leads to the oblique derivative problem that needs to be treated. In case of FEM or FVM, unstructured meshes above the topography will be constructed. The meshless methods like MFS or SBM that are based on the point-masses modelling can be applied for processing the gravity gradients observed by the GOCE satellite mission. To reach precise and high-resolution solutions, an elimination of far zones’ contributions is practically inevitable. This can be performed using the fast multipole method or iterative procedures. In both cases such an elimination process improves conditioning of the system matrix and a numerical stability of the problem.
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The aim of the JSG is also to investigate and develop nonlinear filtering methods that allow adaptive smoothing, which effectively reduces the noise while preserves main structures in data. The proposed approach is based on a numerical solution of partial differential equations using a surface finite volume method. It leads to a semi-implicit numerical scheme of the nonlinear diffusion equation on a closed surface where the diffusivity coefficients depend on a combination of the edge detector and a mean curvature of the filtered function. This will avoid undesirable smoothing of local extremes.
  
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In particular the studies span geometrical observation techniques (e.g. point positioning systems, imaging radar systems), gravimetrical observation techniques (e.g. GRACE, GOCE) and sensors which allow for the direct observation of individual physical processes (e.g., IceSat, SMOS).
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===Objectives===
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The combination of complementary and redundant observation types fosters and improves the understanding of the Earth system. This implies more reliable information on processes and interactions in the subsystems of the Earth which is especially necessary with regard to studies of global change.
 
  
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Among the most important steps are compilation and assessment of background information for individual systems and sensors (mode of operation, sensitivity, accuracy, deficiencies) as well as theoretical studies which (new) information on the Earth system can be gained from a combination of different observation methods.
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The main objectives of the study group are as follows:
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* to develop algorithms for detailed discretization of the real Earth’s surface including the possibility of adaptive refinement procedures,
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* to create unstructured meshes above the topography for the FVM or FEM approach,
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* to develop the FVM, BEM or FEM numerical models for solving the geodetic BVPs that will treat the oblique derivative problem,
 +
* to develop numerical models based on MFS or SBM for processing the GOCE observations,
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* to develop parallel implementations of algorithms using the standard MPI procedures,
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* to perform large-scale parallel computations on clusters with distributed memory,
 +
* to investigate and develop methods for nonlinear diffusion filtering of data on the Earth’s surface where the diffusivity coefficients depend on a combination of the edge detector and a mean curvature of the filtered function,
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* to derive the semi-implicit numerical schemes for the nonlinear diffusion equation on closed surfaces using the surface FVM,
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* and to apply the developed nonlinear filtering methods to real geodetic data.
  
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===Objectives===
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===Program of Activities===
  
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* which processes in the Earth system are insufficiently known and which parameters are imprecisely determined?
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* Active participation at major geodetic workshops and conferences.
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* can the understanding of individual processes be improved by common analysis of different observations types?
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* Organization of group working meetings at main international symposia.
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* which are the target parameters and how are the connections with other variables?
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* Organization of conference sessions.
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* which sensors are available and sensitive for the target parameters?
 
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* which sensors can be used to reduce unwanted signals?
 
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* which are the accuracies, temporal and spatial resolutions of the different data sets and which regions and time spans are covered?
 
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* are the data publicly available or is their access restricted?
 
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* which pre-processing steps are necessary in order to extract the proper information from the raw observation data?
 
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* have the data already been pre-processed? Which methods, models and conventions have been applied? Are there possible error sources or inconsistencies?
 
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* which methods can be applied in order to enhance the information content (e.g. filters)?
 
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* how can the heterogeneous observation types can be combined expediently?
 
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* how do the observation equations look like?
 
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* which methods for parameter estimation can be applied? How can linear dependencies between parameters and rank deficiency problems be solved?
 
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* how can balance equations be regarded in the combination process (e.g. mass and energy balance)?
 
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* are their additional information (models and terrestrial data) which can/must be considered?
 
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* which of the desired parameters can be assessed with the available observation techniques?
 
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* which further parameters are desired and how could appropriate missions for the future look like?
 
  
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The research activities shall be coordinated between the participating scientists and shall be conducted in interdisciplinary collaboration. At all times the group is open for new contacts and members in order to embed the activities in a wide context.
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===Members===
  
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===Membership===
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'' '''Róbert Čunderlík (Slovakia), chair <br /> Karol Mikula (Slovakia), vice-chair''' <br /> Jan Martin Brockmann (Germany) <br /> Walyeldeen Godah (Poland) <br /> Petr Holota (Czech Republic) <br /> Michal Kollár (Slovakia) <br /> Marek Macák (Slovakia) <br />  
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'' '''Florian Seitz, (Germany, Chair)'''<br /> Jean Dickey (USA) <br /> Franz Meyer (USA) <br /> Mahdi Motagh (Germany) <br /> Michael Schmidt (Germany) <br /> Manuela Seitz (Germany) <br /> Xinxing Wang (Germany) <br />''
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Zuzana Minarechová (Slovakia) <br /> Otakar Nesvadba (Czech Republic) <br /> Wolf-Dieter Schuh (Germany) <br />''

Latest revision as of 12:07, 24 April 2016

JSG 0.12: Advanced computational methods for recovery of high-resolution gravity field models

Chairs: Robert Čunderlík (Slovakia)
Affiliation: Comm. 2 and GGOS

Introduction

Efficient numerical methods and HPC (high performance computing) facilities provide new opportunities in many applications in geodesy. The goal of the JSG is to apply numerical methods and/or HPC techniques mostly for gravity field modelling and nonlinear filtering of various geodetic data. The discretization numerical methods like the finite element method (FEM), finite volume method (FVM) and boundary element method (BEM) or the meshless methods like the method of fundamental solutions (MFS) or singular boundary method (SOR) can be efficiently used to solve the geodetic boundary value problems and nonlinear diffusion filtering, or to process e.g. the GOCE observations. Their parallel implementations and large-scale parallel computations on clusters with distributed memory using the MPI (Message Passing Interface) standards allows to solve such problems in spatial domains while obtaining high-resolution numerical solutions.

Our JSG is also open for researchers dealing with the classical approaches of gravity field modelling (e.g. the spherical or ellipsoidal harmonics) that are using high performance computing 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).

Applications of the aforementioned numerical methods for gravity field modelling involve a detailed discretization of the real Earth’s surface considering its topography. It naturally leads to the oblique derivative problem that needs to be treated. In case of FEM or FVM, unstructured meshes above the topography will be constructed. The meshless methods like MFS or SBM that are based on the point-masses modelling can be applied for processing the gravity gradients observed by the GOCE satellite mission. To reach precise and high-resolution solutions, an elimination of far zones’ contributions is practically inevitable. This can be performed using the fast multipole method or iterative procedures. In both cases such an elimination process improves conditioning of the system matrix and a numerical stability of the problem. The aim of the JSG is also to investigate and develop nonlinear filtering methods that allow adaptive smoothing, which effectively reduces the noise while preserves main structures in data. The proposed approach is based on a numerical solution of partial differential equations using a surface finite volume method. It leads to a semi-implicit numerical scheme of the nonlinear diffusion equation on a closed surface where the diffusivity coefficients depend on a combination of the edge detector and a mean curvature of the filtered function. This will avoid undesirable smoothing of local extremes.

Objectives

The main objectives of the study group are as follows:

  • to develop algorithms for detailed discretization of the real Earth’s surface including the possibility of adaptive refinement procedures,
  • to create unstructured meshes above the topography for the FVM or FEM approach,
  • to develop the FVM, BEM or FEM numerical models for solving the geodetic BVPs that will treat the oblique derivative problem,
  • to develop numerical models based on MFS or SBM for processing the GOCE observations,
  • to develop parallel implementations of algorithms using the standard MPI procedures,
  • to perform large-scale parallel computations on clusters with distributed memory,
  • to investigate and develop methods for nonlinear diffusion filtering of data on the Earth’s surface where the diffusivity coefficients depend on a combination of the edge detector and a mean curvature of the filtered function,
  • to derive the semi-implicit numerical schemes for the nonlinear diffusion equation on closed surfaces using the surface FVM,
  • and to apply the developed nonlinear filtering methods to real geodetic data.

Program of Activities

  • Active participation at major geodetic workshops and conferences.
  • Organization of group working meetings at main international symposia.
  • Organization of conference sessions.

Members

Róbert Čunderlík (Slovakia), chair
Karol Mikula (Slovakia), vice-chair
Jan Martin Brockmann (Germany)
Walyeldeen Godah (Poland)
Petr Holota (Czech Republic)
Michal Kollár (Slovakia)
Marek Macák (Slovakia)
Zuzana Minarechová (Slovakia)
Otakar Nesvadba (Czech Republic)
Wolf-Dieter Schuh (Germany)

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