Difference between pages "IC SG1" and "IC SG5"

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<big>'''Theory, implementation and quality assessment of geodetic reference frames'''</big>
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<big>'''JSG 0.5: Multi-sensor combination for the separation of integral
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geodetic signals'''</big>
  
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Chair: ''Y.M. Wang (USA)''<br>
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Chair: ''F. Seitz (Germany)''<br>
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Affiliation:''Comm. 2''
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Affiliation: ''Comm. 2, 3 and GGOS''
  
 
__TOC__
 
__TOC__
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===Introduction===
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===Objectives===
  
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In today's satellite age, the ellipsoidal height can be determined up to 2 cm-accuracy geometrically by the global positioning system (GPS). If geoid models reach the same accuracy, national or global vertical systems can be established in a quick and economical way with cm-accuracy everywhere.
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A large part of the geodetic parameters derived from space geodetic observation techniques are integral quantities of the Earth system. Among the most prominent ones are parameters related to Earth rotation and the gravity field. Variations of those parameters reflect the superposed effect of a multitude of dynamical processes and interactions in various subsystems of the Earth. The integral geodetic quantities provide fundamental and unique information for different balances in the Earth system, in particular for the balances of mass and angular momentum that are directly related to (variations of) the gravity field and Earth rotation. In respective balance equations the geodetic parameters describe the integral effect of exchange processes of mass and angular momentum in the Earth system. In contrast to many other disciplines of geosciences, geodesy is characterized by a very long observation history. Partly, the previously mentioned parameters have been determined over many decades with continuously improved space observation techniques. Thus geodesy provides an excellent data base for the analysis of long term changes in the Earth system and contributes fundamentally to an improved understanding of large-scale processes.
  
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Geoid modeling has been based on Stokes and Molodensky's theories. In both theories, including the theories of gravity and topographic reductions which are fundamentally important for precise geoid computation, approximations and assumptions are made. The evaluation and verification of the effects of assumptions and approximations in the theories are urgently called for. Due to the massive effort on data collection that has improved our knowledge of the Earth's physical surface and its interior, fixed-boundary value problems become practical and useful. Theoretical and numerical studies along this line are not only important in practice, but also may be a fundamental change in physical geodesy.
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However, in general the integral parameter time series cannot be separated into contributions of specific processes without further information. Their separation and therewith their geophysical interpretation requires complementary data from observation techniques that are unequally sensitive for individual effects and/or from numerical models. Activities of the study group are focussed on the development of strategies for the separation of the integral geodetic signals on the basis of modern space-based Earth observation systems. A multitude of simultaneously operating satellite systems with different objectives is available today. They offer a broad spectrum of information on global and regional-scale processes at different temporal resolutions. Within the study group it shall be investigated in which way the combination of heterogeneous data sets allows for the quantification of individual contributors to the balances of mass and angular momentum.
  
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The working group aims at bringing together scientists concerned with all aspects of the diverse areas of geodetically relevant theory and its applications. Its goal is to provide a framework consisting of theories and computational methods to ensure that cm-accurate geoid is achievable.
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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. The study group is primarily affiliated with the IAG commissions 2 (Gravity field) and 3 (Earth rotation and geodynamics).
  
 
===Objectives===
 
===Objectives===
  
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Theoretical research related to precise geoid computations; studies of geodetic boundary values problems (free and fixed boundary value problems); development and refinement of gravity/topographic reduction theories; exploration and implementation of numerical methods of partial differential equations for Earth's gravity field determination (e.g., domain decomposition, spectral combination and others).
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The primary objective of the study group is the development of strategies for multi-sensor combinations with the aim of separating time series of integral geodetic parameters related to Earth rotation and gravity field. The separation of the parameter time series into contributions of individual underlying effects fosters the understanding of dynamical processes and interactions in the Earth system. This is of particular interest in the view of global change.
 +
 
 +
Individual contributions from various subsystems of the Earth shall be quantified and balanced. In particular our investigations focus on the separation of the Earth rotation parameters (polar motion and variations of length-of-day) into contributions of atmospheric and hydrospheric angular momentum variations, and on the separation of GRACE gravity field observations over continents into the contributions of individual hydrological storage compartments, such as groundwater, surface water, soil moisture and snow.
 +
Investigations in the frame of the study group will exploit the synergies of various observation systems (satellite altimetry, optical and radar remote sensing, SMOS, and others) for the separation of the signals and combine their output with numerical models. Among the most important steps are compilation and assessment of background information for individual observation 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.
 +
 
 +
In particular the research comprises the following topics:
 +
* potential und usability of contemporary spaceborne and terrestrial sensors for an improved understanding of processes within atmosphere and hydrosphere,
 +
* analysis of accuracy, temporal and spatial resolution and coverage of different data sets,
 +
* theoretical and numerical studies on the combination of heterogeneous observation types; this comprehends investigations on appropriate methods for parameter estimation including error propagation, the analysis of linear dependencies between parameters and the solution of rank deficiency problems,
 +
* mathematical methods for the enhancement of the information content (e.g., filters),
 +
* quantification of variations of mass and angular momentum in different subsystems from multi-sensor analysis.
 +
* analysis of the consistencies of balances between individ-ual effects and integral geodetic parameters on different spatial scales
 +
* formulation of recommendations for future research and (if possible) for future satellite missions on the basis of balance inconsistencies
  
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In more details, this includes:
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===Planned Activities===
  
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* Studies of the effect of topographic density variations on the Earth's gravity field, especially the geoid.
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* Set-up of a JSG webpage for dissemination of information (activities and a bibliographic list of references) and for presentation and communication of research results.
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* Rigorous yet efficient calculation of the topographic effects, refinement of the topographic and gravity reductions.
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* Organization of conference sessions / workshops:
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* Studies on harmonic downward continuations.
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** planned in 2013: Conference Session in the Hotine Marussi Symposium
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* Non-linear effects of the geodetic boundary value problems on the geoid determinations.
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** planned in 2014: 2nd workshop on the Quality of Geodetic Observing and Monitoring Systems (QuGOMS’ 14)
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* Optimal combination of global gravity models with local gravity data.
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* Common publications of SG members
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* Exploration of numerical methods in solving the geodetic boundary value problems (domain decomposition, finite elements, and others)
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* Common fund raising activities (e.g., for PhD. positions)
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* Studies on data requirements, data quality, distribution and sample rate, for a cm- accurate geoid.
 
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* Studies on the time variations of the geoid caused by geodynamics.
 
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* Studies on the interdisciplinary approach for marine geoid determination, e.g., research on realization of a global geoid consistent with the global mean sea surface observed by satellites.
 
  
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===Program of activities===
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===Principal Scientific Outcome/Results===
  
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* Organization of meetings and conferences.
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By the end of the 4-year period 2011-2015 the following outcome shall be achieved:
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* Organizing WG meetings or sessions, in coincidence with a larger event, if the presence of working group members appears sufficiently large.
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Mature experience in geodetic multi-sensor data combina-tion including data availability, formats, combination strategies and accuracy aspects
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* Email discussion and electronic exchange.
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Numerical results for separated hydrological contributions to integral mass variations observed by GRACE for selected study areas.
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* Launching a web page for dissemination of information, expressing aims, objectives, and discussions.
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Numerical results for separated atmospheric/hydrospheric contributions Earth rotation parameters on seasonal to inter-annual time scales
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* Monitoring and reporting activities of working group members and interested external individuals.
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Initiation of at least one common funded project with posi-tions for PhD students working in the topical field of the study group
  
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===Membership===
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===Members===
  
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'' '''Y.M. Wang, (USA, chair)'''<br /> W. Featherstone, Australia<br /> N. Kühtreiber, Austria<br /> H. Moritz, Austria<br /> M.G. Sideris, Canada<br /> M. Véronneau, Canada<br /> J. Huang, Canada<br /> M. Santos, Canada<br /> J.C. Li, China<br /> D.B. Cao, China<br /> W.B. Shen, China<br /> F. Mao, China<br /> Z. Martinec, Czech Republic<br /> R. Forsberg, Denmark<br /> O. Anderson, Denmark<br /> H. Abd-Elmotaal, Egypt<br /> H. Denker, Germany<br /> B. Heck, Germany<br /> W. Freeden, Germany<br /> J. H. Kwon, Korea<br /> L. Sjöberg, Sweden<br /> D. Roman, USA<br /> J. Saleh, USA<br /> D. Smith USA<br />''
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'' '''Florian Seitz (Germany), chair'''<br />Sarah Abelen (Germany)<br />Rodrigo Abarca del Rio (Chile)<br />Andreas Güntner (Germany)
 +
<br />Karin Hedman (Germany)<br />Franz Meyer (USA)<br />Michael Schmidt (Germany)<br />Manuela Seitz (Germany)<br />Alka Singh (India)<br />''

Revision as of 11:48, 2 July 2012

JSG 0.5: Multi-sensor combination for the separation of integral geodetic signals

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

Objectives

A large part of the geodetic parameters derived from space geodetic observation techniques are integral quantities of the Earth system. Among the most prominent ones are parameters related to Earth rotation and the gravity field. Variations of those parameters reflect the superposed effect of a multitude of dynamical processes and interactions in various subsystems of the Earth. The integral geodetic quantities provide fundamental and unique information for different balances in the Earth system, in particular for the balances of mass and angular momentum that are directly related to (variations of) the gravity field and Earth rotation. In respective balance equations the geodetic parameters describe the integral effect of exchange processes of mass and angular momentum in the Earth system. In contrast to many other disciplines of geosciences, geodesy is characterized by a very long observation history. Partly, the previously mentioned parameters have been determined over many decades with continuously improved space observation techniques. Thus geodesy provides an excellent data base for the analysis of long term changes in the Earth system and contributes fundamentally to an improved understanding of large-scale processes.

However, in general the integral parameter time series cannot be separated into contributions of specific processes without further information. Their separation and therewith their geophysical interpretation requires complementary data from observation techniques that are unequally sensitive for individual effects and/or from numerical models. Activities of the study group are focussed on the development of strategies for the separation of the integral geodetic signals on the basis of modern space-based Earth observation systems. A multitude of simultaneously operating satellite systems with different objectives is available today. They offer a broad spectrum of information on global and regional-scale processes at different temporal resolutions. Within the study group it shall be investigated in which way the combination of heterogeneous data sets allows for the quantification of individual contributors to the balances of mass and angular momentum.

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. The study group is primarily affiliated with the IAG commissions 2 (Gravity field) and 3 (Earth rotation and geodynamics).

Objectives

The primary objective of the study group is the development of strategies for multi-sensor combinations with the aim of separating time series of integral geodetic parameters related to Earth rotation and gravity field. The separation of the parameter time series into contributions of individual underlying effects fosters the understanding of dynamical processes and interactions in the Earth system. This is of particular interest in the view of global change.

Individual contributions from various subsystems of the Earth shall be quantified and balanced. In particular our investigations focus on the separation of the Earth rotation parameters (polar motion and variations of length-of-day) into contributions of atmospheric and hydrospheric angular momentum variations, and on the separation of GRACE gravity field observations over continents into the contributions of individual hydrological storage compartments, such as groundwater, surface water, soil moisture and snow. Investigations in the frame of the study group will exploit the synergies of various observation systems (satellite altimetry, optical and radar remote sensing, SMOS, and others) for the separation of the signals and combine their output with numerical models. Among the most important steps are compilation and assessment of background information for individual observation 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.

In particular the research comprises the following topics:

  • potential und usability of contemporary spaceborne and terrestrial sensors for an improved understanding of processes within atmosphere and hydrosphere,
  • analysis of accuracy, temporal and spatial resolution and coverage of different data sets,
  • theoretical and numerical studies on the combination of heterogeneous observation types; this comprehends investigations on appropriate methods for parameter estimation including error propagation, the analysis of linear dependencies between parameters and the solution of rank deficiency problems,
  • mathematical methods for the enhancement of the information content (e.g., filters),
  • quantification of variations of mass and angular momentum in different subsystems from multi-sensor analysis.
  • analysis of the consistencies of balances between individ-ual effects and integral geodetic parameters on different spatial scales
  • formulation of recommendations for future research and (if possible) for future satellite missions on the basis of balance inconsistencies

Planned Activities

  • Set-up of a JSG webpage for dissemination of information (activities and a bibliographic list of references) and for presentation and communication of research results.
  • Organization of conference sessions / workshops:
    • planned in 2013: Conference Session in the Hotine Marussi Symposium
    • planned in 2014: 2nd workshop on the Quality of Geodetic Observing and Monitoring Systems (QuGOMS’ 14)
  • Common publications of SG members
  • Common fund raising activities (e.g., for PhD. positions)

Principal Scientific Outcome/Results

By the end of the 4-year period 2011-2015 the following outcome shall be achieved: Mature experience in geodetic multi-sensor data combina-tion including data availability, formats, combination strategies and accuracy aspects Numerical results for separated hydrological contributions to integral mass variations observed by GRACE for selected study areas. Numerical results for separated atmospheric/hydrospheric contributions Earth rotation parameters on seasonal to inter-annual time scales Initiation of at least one common funded project with posi-tions for PhD students working in the topical field of the study group

Members

Florian Seitz (Germany), chair
Sarah Abelen (Germany)
Rodrigo Abarca del Rio (Chile)
Andreas Güntner (Germany)
Karin Hedman (Germany)
Franz Meyer (USA)
Michael Schmidt (Germany)
Manuela Seitz (Germany)
Alka Singh (India)

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