Difference between revisions of "IC SG3"

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<big>'''JSG 0.3: Comparison of current methodologies in regional gravity field modelling'''</big>
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<big>'''Configuration analysis of Earth oriented space techniques'''</big>
  
Chairs: ''M. Schmidt (Germany), Ch. Gerlach (Germany)''<br>
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Chair: ''F. Seitz (Germany)''<br>
Affiliation: ''Comm. 2, 3''
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Affiliation: ''Comm. 3, 2, 1''
  
 
__TOC__
 
__TOC__
 
===Introduction===
 
===Introduction===
  
Traditionally the gravitational potential of the Earth and other celestial bodies is modelled as a series expansion in terms of spherical harmonics. Although this representation is technically possible for ultra-high expansions, it is well-known that spherical harmonic approaches cannot represent data of heterogeneous density and quality in a proper way. In order to overcome these and other deficiencies regional modelling comes into question.
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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.
  
In the last years many groups have developed sophisticated approaches for regional modelling, e.g., the expansion of the gravity field or functionals of the field in terms of spherical (radial) base functions. Analogously to spherical harmonic approaches, also in regional modelling the unknown model parameters, i.e., the coefficients of the series expansion, can be either determined by means of numerical integration or as the solution of a parameter estimation process. Numerical integration techniques are widely used in the mathematical community and provide efficient and stable solutions. However, numerical integration techniques suffer from important disadvantages. Among others these methods (1) require the input data to be given on a spherical integration grid, (2) cannot provide estimated error variances and covariances of the model parameters and (3) have difficulties to handle the combination of data from different measurement techniques. Due to these disadvantages, parameter estimation is the preferred strategy in the geodetic community. Although solutions in regional modelling based on parameter estimation are generated by several groups since many years, a large number of unsolved problems and open questions still remain. They mostly arise from the condition of the normal equation system and are therefore directly connected to the parametrization of the gravity field, the type and distribution of observation data, the choice and location of base functions, possible regularisation schemes, etc.
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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.
  
The aim of the JSG is to find guidelines on suitable strategies for setting up the parameter estimation of regional gravity field modelling. This includes appropriate strategies for the combination of satellite, airborne and terrestrial data. The focus of the JSG is on the methodological foundation of regional gravity field modelling based on series expansions in terms of localizing base functions. Therefore, numerical studies will be concentrated on simulations based on synthetic data. It is not the aim of the JSG to process and compare solutions from real data.
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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.
  
===Objectives===
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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).
 +
 
 +
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.
  
The main objectives of this JSG are:
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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.
* to collect information of available methodologies and strategies for regional modelling, including
 
** the type of base functions (splines, wavelets, Slepian function, Mascons, etc.),
 
** the point grids for placing the functions (standard grid, icosaeder, Reuter grid, etc. on a sphere, ellipsoid, etc.),
 
** the choice and establishment of an appropriate adjustment model (combination strategy, variance component estimation, rank deficiency problems, e.g., due to downward continuation, etc.),
 
** the consideration of model errors (truncation errors, edge effects, leakage, etc.),
 
** the specific field of application,
 
* to analyze the collected information in order to find specific properties of the different approaches and to find, why certain strategies have been chosen,
 
* to create a benchmark data set for comparative numerical studies,
 
* to carry out numerical comparisons between different solution strategies for estimating the model parameters and to validate the results with other approaches (spherical harmonic models, least-squares collocation, etc.),
 
* to quantify and interpret the differences of the comparisons with a focus on detection, explanation and treatment of inconsistencies and possible instabilities of the different approaches,
 
* to create guidelines for generating regional gravity solutions,
 
* to outline standards and conventions for future regional gravity products.
 
* Comparable work outside gravity field determination, e.g., in the mathematical communities and in geomagnetic field determination will be taken into account.
 
* To achieve the objectives, the JSG interacts and collaborates with other ICCT JSGs as well as IAG Commission 2. As a matter of fact, the outcomes of the JSG can be also used by other IAG commissions, especially in Commission 3.
 
* The JSG's work will be distributed to IAG sister associations through respective members.
 
  
===Program of Activities===
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===Objectives===
  
The JSG’s program of activities will include organization of SG meetings and of one or more scientific workshops on regional modelling
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* which processes in the Earth system are insufficiently known and which parameters are imprecisely determined?
participation in respective symposia (EGU, AGU, etc.), publication of important findings in proper journals, maintaining a website for general information as well as for internal exchange of data sets and results, supporting ICCT activities.
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* can the understanding of individual processes be improved by common analysis of different observations types?
 +
* which are the target parameters and how are the connections with other variables?
 +
* which sensors are available and sensitive for the target parameters?
 +
* which sensors can be used to reduce unwanted signals?
 +
* which are the accuracies, temporal and spatial resolutions of the different data sets and which regions and time spans are covered?
 +
* are the data publicly available or is their access restricted?
 +
* which pre-processing steps are necessary in order to extract the proper information from the raw observation data?
 +
* have the data already been pre-processed? Which methods, models and conventions have been applied? Are there possible error sources or inconsistencies?
 +
* which methods can be applied in order to enhance the information content (e.g. filters)?
 +
* how can the heterogeneous observation types can be combined expediently?
 +
* how do the observation equations look like?
 +
* which methods for parameter estimation can be applied? How can linear dependencies between parameters and rank deficiency problems be solved?
 +
* how can balance equations be regarded in the combination process (e.g. mass and energy balance)?
 +
* are their additional information (models and terrestrial data) which can/must be considered?
 +
* which of the desired parameters can be assessed with the available observation techniques?
 +
* which further parameters are desired and how could appropriate missions for the future look like?
  
===Members===
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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.
  
'' '''Michael Schmidt (Germany), chair<br />Christian Gerlach (Germany), chair'''<br />Katrin Bentel (Norway)<br />Annette Eicker (Germany)<br />Indridi Einarsson (Denmark)<br />Junyi Guo (USA)<br />Majid Naeimi (Germany)<br />Isabelle Panet (France)<br />
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===Membership===
Judith Schall (Germany)<br />Uwe Schäfer (Germany)<br />Frederick Simons (USA)<br />C.K. Shum (USA)<br />Matthias Weigelt (Germany)
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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 />''
<br />Gongyou Wu (China)<br />''
 

Revision as of 10:26, 28 April 2010

Configuration analysis of Earth oriented space techniques

Chair: F. Seitz (Germany)
Affiliation: Comm. 3, 2, 1

Introduction

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.

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.

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.

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).

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.

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.

Objectives

  • which processes in the Earth system are insufficiently known and which parameters are imprecisely determined?
  • can the understanding of individual processes be improved by common analysis of different observations types?
  • which are the target parameters and how are the connections with other variables?
  • which sensors are available and sensitive for the target parameters?
  • which sensors can be used to reduce unwanted signals?
  • which are the accuracies, temporal and spatial resolutions of the different data sets and which regions and time spans are covered?
  • are the data publicly available or is their access restricted?
  • which pre-processing steps are necessary in order to extract the proper information from the raw observation data?
  • have the data already been pre-processed? Which methods, models and conventions have been applied? Are there possible error sources or inconsistencies?
  • which methods can be applied in order to enhance the information content (e.g. filters)?
  • how can the heterogeneous observation types can be combined expediently?
  • how do the observation equations look like?
  • which methods for parameter estimation can be applied? How can linear dependencies between parameters and rank deficiency problems be solved?
  • how can balance equations be regarded in the combination process (e.g. mass and energy balance)?
  • are their additional information (models and terrestrial data) which can/must be considered?
  • which of the desired parameters can be assessed with the available observation techniques?
  • which further parameters are desired and how could appropriate missions for the future look like?

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.

Membership

Florian Seitz, (Germany, Chair)
Jean Dickey (USA)
Franz Meyer (USA)
Mahdi Motagh (Germany)
Michael Schmidt (Germany)
Manuela Seitz (Germany)
Xinxing Wang (Germany)