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

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(Introduction)
 
(Planned Activities)
 
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<big>'''JSG 0.1: Application of time-series analysis in geodesy'''</big>
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<big>'''JSG 0.5: Multi-sensor combination for the separation of integral
 +
geodetic signals'''</big>
  
Chair: ''W. Kosek (Poland)''<br>
+
Chair: ''F. Seitz (Germany)''<br>
Affiliation:''GGOS, all commissions''
+
Affiliation: ''Comm. 2, 3 and GGOS''
  
 
__TOC__
 
__TOC__
===Introduction===
+
===Objectives===
  
Observations provided by modern space geodetic techniques (geometric and gravimetric) deliver a global picture of dynamics of the Earth. Such observations are usually represented as time series which describe (1) changes of surface geometry of the Earth due to horizontal and vertical deformations of the land, ocean and cryosphere, (2) fluctuations in the orientation of the Earth divided into precession, nutation, polar motion and spin rate, and (3) variations of the Earth’s gravitational field and the centre of mass of the Earth. The vision and goal of GGOS is to understand the dynamic Earth’s system by quantifying our planet’s changes in space and time and integrate all observations and elements of the Earth’s system into one unique physical and mathematical model. To meet the GGOS requirements, all temporal variations of the Earth’s dynamics – which represent the total and hence integral effect of mass exchange between all elements of Earth’s system including atmosphere, ocean and hydrology – should be properly described by time series methods.
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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.
  
Various time series methods have been applied to analyze such geodetic and related geophysical time series in order to better understand the relation between all elements of the Earth’s system. The interactions between different components of the Earth’s system are very complex, thus the nature of the considered signals in the geodetic time series is mostly wideband, irregular and non-stationary. Therefore, the application of time frequency analysis methods based on wavelet coefficients – e.g. time-frequency cross-spectra, coherence and semblance – is necessary to reliably detect the features of the temporal or spatial variability of signals included in various geodetic data, and other associated geophysical data.
+
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.
  
Geodetic time series may include, for instance, temporal variations of site positions, tropospheric delay, ionospheric total electron content, masses in specific water storage compartments or estimated orbit parameters as well as surface data including gravity field, sea level and ionosphere maps. The main problems to be scrutinized concern the estimation of deterministic (including trend and periodic variations) and stochastic (non-periodic variations and random fluctuations) components of the time series along with the application of the appropriate digital filters for extracting specific components with a chosen frequency bandwidth. The application of semblance filtering enables to compute the common signals, understood in frame of the time-frequency approach, which are embedded in various geodetic/geophysical time series.
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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).
  
Numerous methods of time series analysis may be employed for processing raw data from various geodetic measurements in order to promote the quality level of signal enhancement. The issue of improvement of the edge effects in time series analysis may also be considered. Indeed, they may either affect the reliability of long-range tendency (trends) estimated from data or the real-time processing and prediction.
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===Objectives===
  
The development of combination strategies for time- and space-dependent data processing, including multi-mission sensor data, is also very important. Numerous observation techniques, providing data with different spatial and temporal resolutions and scales, can be combined to compute the most reliable geodetic products. It is now known that incorporating space variables in the process of geodetic time series modelling and prediction can lead to a significant improvement of the prediction performance. Usually multi-sensor data comprises a large number of individual effects, e.g., oceanic, atmospheric and hydrological contributions. In Earth system analysis one key point at present and in the future will be the development of separation techniques. In this context principal component analysis and related techniques can be applied.
+
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.
  
===Objectives===
+
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===
  
* To study geodetic time series and their geophysical causes in different frequency bands using time series analysis methods, mainly for better understanding of their causes and prediction improvement.
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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.
* The evaluation of appropriate covariance matrices corre-sponding to the time series by applying the law of error propagation, including weighting schemes, regulariza-tion, etc.
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* Organization of conference sessions / workshops:
* Determining statistical significance levels of the results obtained by different time series analysis methods and algorithms applied to geodetic time series.
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** planned in 2013: Conference Session in the Hotine Marussi Symposium
* The comparison of different time series analysis methods and their recommendation, with a particular emphasis put on solving problems concerning specific geodetic data.
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** planned in 2014: 2nd workshop on the Quality of Geodetic Observing and Monitoring Systems (QuGOMS’ 14)
* Developing and implementing the algorithms – aiming to seek and utilize spatio-temporal correlations – for geo-detic time series modelling and prediction.
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* Common publications of SG members
* Better understanding of how large-scale environmental processes, such as for instance oceanic and atmospheric oscillations and climate change, impact modelling strate-gies employed for numerous geodetic data.
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* Common fund raising activities (e.g., for PhD. positions)
* Developing combination strategies for time- and space-dependent data obtained from different geodetic observa-tions.
 
* Developing separation techniques for integral measure-ments in individual contributions.
 
  
 +
===Principal Scientific Outcome/Results===
  
===Program of activities===
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By the end of the 4-year period 2011-2015 the following outcome shall be achieved:
Updating the webpage, so that the information on time series analysis and its application in geodesy (including relevant multidisciplinary publications and the unification of terminology applied in time series analysis) will be available.
+
Mature experience in geodetic multi-sensor data combina-tion including data availability, formats, combination strategies and accuracy aspects
Participating in working meetings at the international sym-posia and presenting scientific results at the appropriate sessions.
+
Numerical results for separated hydrological contributions to integral mass variations observed by GRACE for selected study areas.
Collaboration with other working groups dealing with geo-detic time-series e.g. Cost ES0701 Improved constraints on models of GIA or the Climate Change Working Group.
+
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===
 
===Members===
  
'' '''W. Kosek (Poland), chair'''<br /> R. Abarca del Rio (Chile)<br /> O. Akyilmaz (Turkey)<br /> J. Böhm (Austria)<br /> L. Fernandez (Argentina)<br /> R. Gross (USA)<br /> M. Kalarus (Poland)<br /> M. O. Karslioglu (Turkey)<br /> H. Neuner (Germany)<br /> T. Niedzielski (Poland)<br /> S. Petrov (Russia)<br /> W. Popinski (Poland)<br /> M. Schmidt (Germany)<br /> M. van Camp (Belgium)<br /> O. de Viron (France)<br /> J. Vondrák (Czech Republic)<br /> D. Zheng (China)<br /> Y. Zhou (China)<br />''
+
'' '''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 10:48, 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)