Difference between revisions of "IC SG8"

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<big>'''JSG 0.17: Multi-GNSS theory and algorithms'''</big>
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<big>'''Towards cm-accurate geoid - Theories, computational methods and validation'''</big>
  
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Chair: ''Amir Khodabandeh (Australia)''<br>
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Chair: ''Y.M. Wang (USA)''<br>
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Affiliation:''Comm. 1, 4 and GGOS''
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Affiliation:''Comm. 2''
  
 
__TOC__
 
__TOC__
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===Introduction===
  
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===Introduction===
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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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In recent years, we are witnessing rapid development in the satellite-based navigation and positioning systems. Next to the modernization of the GPS dual-frequency signals to the triple-frequency signals, the GLONASS satellites have been revitalized and become fully operational. The new global and regional satellite constellations are also joining the family of the navigation systems. These additions are the two global systems of Galileo and BeiDou satellites as well as the two regional systems of QZSS and IRNSS satellites. This namely means that many more satellites will be visible to the GNSS users, transmitting data on many more frequencies than the current GPS dual-frequency setup, thereby expecting considerable improvement in the performance of the positioning and non-positioning GNSS applications.
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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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Such a proliferation of multi-system, multi-frequency data demands rigorous theoretical frameworks, models and algorithms that enable the near-future multiple GNSSs to serve as a high-accuracy and high-integrity tool for the Earth-, atmospheric- and space-sciences. For instance, recent studies have revealed the existence of non-zero inter-system and inter-system-type biases that, if ignored, result in a catastrophic failure of integer ambiguity resolution, thus deteriorating the corresponding ambiguity resolved solutions. The availability of the new multi-system, multi-frequency data does therefore appeal proper mathematical models so as to enable one to correctly integrate such data, thus correctly linking the data to the estimable parameters of interest.
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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.
  
 
===Objectives===
 
===Objectives===
  
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The main objectives of this study group are:
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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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* to identify and investigate challenges that are posed by processing and integrating the data of the next generation navigation and positioning satellite systems,
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* to develop new functional and stochastic models linking the multi-GNSS observations to the positioning and non-positioning parameters,
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In more details, this includes:
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* to derive optimal methods that are capable of handling the data-processing of large-scale networks of mixed-receiver types tracking multi-GNSS satellites,
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* to conduct an in-depth analysis of the systematic satellite- and receiver-dependent biases that are present either within one or between multiple satellite systems,
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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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* to develop rigorous quality-control and integrity tools for evaluating the reliability of the multi-GNSS data and guarding the underlying models against any mis-modelled effects,
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* Rigorous yet efficient calculation of the topographic effects, refinement of the topographic and gravity reductions.
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* to access the compatibility of the real-time multi-GNSS input parameters for positioning and non-positioning products,
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* Studies on harmonic downward continuations.
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* to articulate the theoretical developments and findings through the journals and conference proceedings.
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* Non-linear effects of the geodetic boundary value problems on the geoid determinations.
 +
* Optimal combination of global gravity models with local gravity data.
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* Exploration of numerical methods in solving the geodetic boundary value problems (domain decomposition, finite elements, and others)
 +
* Studies on data requirements, data quality, distribution and sample rate, for a cm- accurate geoid.
 +
* 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.
  
 
===Program of activities===
 
===Program of activities===
  
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While the investigation will be strongly based on the theoretical aspects of the multi-GNSS observation modelling and challenges, they will be also accompanied by numerical studies of both the simulated and real-world data. Given the expertise of each member, the underlying studies will be conducted on both individual and collaborative bases. The outputs of the group study is to provide the geodesy and GNSS communities with well-documented models and algorithmic methods through the journals and conference proceedings.
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* Organization of meetings and conferences.
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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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* Email discussion and electronic exchange.
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* Launching a web page for dissemination of information, expressing aims, objectives, and discussions.
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* Monitoring and reporting activities of working group members and interested external individuals.
  
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===Members===
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===Membership===
  
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'' '''Amir Khodabandeh (Australia), chair''' <br /> Peter J.G. Teunissen (Australia) <br /> Pawel Wielgosz (Poland) <br /> Bofeng Li (China) <br /> Simon Banville (Canada) <br /> Nobuaki Kubo (Japan) <br /> Ali Reza Amiri-Simkooei (Iran) <br /> Gabriele Giorgi (Germany) <br />
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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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Thalia Nikolaidou (Canada) <br />''
 

Revision as of 11:08, 10 June 2008

Towards cm-accurate geoid - Theories, computational methods and validation

Chair: Y.M. Wang (USA)
Affiliation:Comm. 2

Introduction

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.

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.

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.

Objectives

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).

In more details, this includes:

  • Studies of the effect of topographic density variations on the Earth's gravity field, especially the geoid.
  • Rigorous yet efficient calculation of the topographic effects, refinement of the topographic and gravity reductions.
  • Studies on harmonic downward continuations.
  • Non-linear effects of the geodetic boundary value problems on the geoid determinations.
  • Optimal combination of global gravity models with local gravity data.
  • Exploration of numerical methods in solving the geodetic boundary value problems (domain decomposition, finite elements, and others)
  • Studies on data requirements, data quality, distribution and sample rate, for a cm- accurate geoid.
  • Studies on the time variations of the geoid caused by geodynamics.
  • 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.

Program of activities

  • Organization of meetings and conferences.
  • Organizing WG meetings or sessions, in coincidence with a larger event, if the presence of working group members appears sufficiently large.
  • Email discussion and electronic exchange.
  • Launching a web page for dissemination of information, expressing aims, objectives, and discussions.
  • Monitoring and reporting activities of working group members and interested external individuals.

Membership

Y.M. Wang, (USA, chair)
W. Featherstone, Australia
N. Kühtreiber, Austria
H. Moritz, Austria
M.G. Sideris, Canada
M. Véronneau, Canada
J. Huang, Canada
M. Santos, Canada
J.C. Li, China
D.B. Cao, China
W.B. Shen, China
F. Mao, China
Z. Martinec, Czech Republic
R. Forsberg, Denmark
O. Anderson, Denmark
H. Abd-Elmotaal, Egypt
H. Denker, Germany
B. Heck, Germany
W. Freeden, Germany
J. H. Kwon, Korea
L. Sjöberg, Sweden
D. Roman, USA
J. Saleh, USA
D. Smith USA

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