Difference between revisions of "IC SG1"

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<big>'''JSG 0.10: High-rate GNSS'''</big>
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<big>'''Theory, implementation and quality assessment of geodetic reference frames'''</big>
  
Chair: ''Mattia Crespi (Italy)''<br>
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Chair: ''Y.M. Wang (USA)''<br>
Affiliation:''Commissions 1, 3 4 and GGOS''
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Affiliation:''Comm. 2''
  
 
__TOC__
 
__TOC__
 
 
===Introduction===
 
===Introduction===
  
Global Navigation Satellite Systems (GNSS) have become for a long time an indispensable tool to get accurate and reliable information about positioning and timing; in addition, GNSS are able to provide information related to physical properties of media passed through by GNSS signals. Therefore, GNSS play a central role both in geodesy and geomatics and in several branches of geophysics, representing a cornerstone for the observation and monitoring of our planet.
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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.
  
So, it is not surprising that, from the very beginning of the GNSS era, the goal was pursued to widen as much as possible the range in space (from local to global) and time (from short to long term) of the observed phenomena, in order to cover the largest possible field of applications, both in science and in engineering; two complementary, but primary as well, goals were, obviously, to get these information with the highest accuracy and in the shortest time.  
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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.
  
The advances in technology and the deployment of new constellations, after GPS (in the next years will be completed the European Galileo, the Chinese Beidou and the Japanese QZSS) remarkably contributed to transform this three-goals dream in reality, but still remain significant challenges when very fast phenomena have to be observed, mainly if real-time results are looked for.
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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.
  
Actually, for almost 15 years, starting from the noble birth in seismology, and the very first experiences in structural monitoring, high-rate GNSS has demonstrated its usefulness and power in providing precise positioning information in fast time-varying environments. At the beginning, high-rate observations were mostly limited at 1 Hz, but the technology development provided GNSS equipment (in some cases even at low-cost) able to collect measurements at much higher rates, up to 100 Hz, therefore opening new possibilities, and meanwhile new challenges and problems.
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===Objectives===
  
So, it is necessary to think about how to optimally process this potential huge heap of data, in order to supply information of high value for a large (and likely increasing) variety of applications, some of them listed hereafter without the claim to be exhaustive: better understanding of the geophysical/geodynamical processes mechanics; monitoring of ground shaking and displacement during earthquakes, also for contribution to tsunami early warning; tracking the fast variations of the ionosphere; real-time controlling landslides and the safety of structures; providing detailed trajectories and kinematic parameters (not only position, but also velocity and acceleration) of high dynamic platforms such as airborne sensors, high-speed terrestrial vehicles and even athlete and sport vehicles monitoring.
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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).
  
Further, due to the contemporary technological development of other sensors (hereafter referred as ancillary sensors) related to positioning and kinematics able to collect data at high-rate (among which MEMS accelerometers and gyros play a central role, also for their low-cost), the feasibility of a unique device for high-rate observations embedding GNSS receiver and MEMS sensors is real, and it open, again, new opportunities and problems, first of all related to sensors integration.
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In more details, this includes:
 
 
All in all, it is clear that high-rate GNSS (and ancillary sensors) observations represent a great resource for future investigations in Earth sciences and applications in engineering, meanwhile stimulating a due attention from the methodological point of view in order to exploit their full potential and extract the best information.  This is the why it is worth to open a focus on high-rate (and, if possible, real-time) GNSS within ICCT.
 
 
 
===Objectives===
 
  
* To realize the inventories of:
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* Studies of the effect of topographic density variations on the Earth's gravity field, especially the geoid.
- the available and applied methodologies for high-rate GNSS, in order to highlight their pros and cons and the open problems <br />
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* Rigorous yet efficient calculation of the topographic effects, refinement of the topographic and gravity reductions.
- the present and wished applications of high-rate GNSS for science and engineering, with a special concern to the estimated quantities (geodetic, kinematic, physical), in order to focus on related problems (still open and possibly new) and draw future challenges  <br />
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* Studies on harmonic downward continuations.
- the technology (hw, both for GNSS and ancillary sensors, and sw, possibly FOSS), pointing out what is ready and what is coming, with a special concern for the supplied observations and for their functional and stochastic modeling with the by-product of establishing a standardized terminology  <br />
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* Non-linear effects of the geodetic boundary value problems on the geoid determinations.
* To address known (mostly cross-linked) problems related to high-rate GNSS as (not an exhaustive list): revision and refinement of functional and stochastic models; evaluation and impact of observations time-correlation; impact of multipath and constellation change; outliers detection and removal; issues about GNSS constellations interoperability; ancillary sensors evaluation, cross-calibration and  integration
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* Optimal combination of global gravity models with local gravity data.
* To address the new problems and future challanges arised from the inventories
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* Exploration of numerical methods in solving the geodetic boundary value problems (domain decomposition, finite elements, and others)
* To investigate about the interaction with present real-time global (IGS-RTS, EUREF-IP, etc.) and regional/local positioning services: how can these services support high-rate GNSS observations and, on reverse, how can they benefit of high-rate GNSS observations
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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.
  
 
===Program of activities===
 
===Program of activities===
  
* To launch a questionnaire for the above mentioned inventory of methodologies, applications and technologies.
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* Organization of meetings and conferences.
* To open a web page with information concerning high-rate GNSS and its wide applications in science and engineering, with special emphasis on exchange of ideas, provision and updating bibliographic list of references of research results and relevant publications from different disciplines.
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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.
* To launch the proposal for two (one science and the other engineering oriented) state-of-the-art review papers in high-rate GNSS co-authored by the JSG Members.
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* Email discussion and electronic exchange.
* To organize a session at the forthcoming Hotine-Marussi symposium.
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* Launching a web page for dissemination of information, expressing aims, objectives, and discussions.
* To promote sessions and presentation of the  research results at international symposia both related to Earth science (IAG/IUGG, EGU, AGU, EUREF, IGS) and engineering (workshops and congresses in structural and geotechnical engineering).
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* Monitoring and reporting activities of working group members and interested external individuals.
  
===Members===
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===Membership===
  
'' '''Mattia Crespi (Italy), chair''' <br /> Juan Carlos Baez (Chile) <br /> Elisa Benedetti (United Kingdom) <br /> Geo Boffi (Switzerland) <br /> Gabriele Colosimo (Switzerland) <br /> Athanasios Dermanis (Greece) <br /> Roberto Devoti (Italy) <br /> Jeff Freymueller (USA) <br /> Joao Francisco Galera Monico (Brazil) <br /> Jianghui Geng (Germany) <br /> Kosuke Heki (Japan) <br /> Melvin Hoyer (Venezuela) <br /> Nanthi Nadarajah (Australia) <br /> Yusaku Ohta (Japan) <br /> Ruey-Juin Rau (Taiwan) <br /> Eugenio Realini (Italy) <br /> Chris Rizos (Australia) <br /> Nico Sneeuw (Germany) <br /> Peiliang Xu (Japan) <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 />''

Revision as of 12:48, 22 April 2008

Theory, implementation and quality assessment of geodetic reference frames

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