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>
  
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Chair: ''Mattia Crespi (Italy)''<br>
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Chair: ''A. Dermanis (Greece)''<br>
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Affiliation:''Commissions 1, 3 4 and GGOS''
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Affiliation:''Comm. 1, IERS''
  
 
__TOC__
 
__TOC__
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===Introduction===
 
===Introduction===
  
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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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The realization of a reference system by means of a reference frame, in the form of coordinate time series or coordinate functions for a global set of control stations is a complicated procedure. It involves input data from various space techniques each one based on its own advanced modelling and observation analysis techniques, as well as, criteria for the optimal selection of the time evolution of the reference frame among all data compatible possibilities. The relevant “observed” coordinate time series demonstrate significant signals of periodic, non- periodic variations and discontinuities, which pose the challenge of departing from the current ITRF model of linear time evolution, realized by reference epoch coordinates and constant velocities. The final product needs proper quality measures, which take also into account the possible modelling discrepancies, systematic errors and noise level of each particular space technique. The connection with a celestial frame by means of earth orientation parameters (EOPs) and current geophysical plate motion hypotheses necessitate the study of the compatibility of the geodetically established reference system with reference systems introduced in theoretical studies of the earth rotation and in theoretical geophysics. The working group is primarily aiming in problem identification, outlining of possible solution directions and motivation of relevant scientific research.  
  
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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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===Objectives===
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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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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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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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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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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.
 
  
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===Objectives===
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* Study of models for time-continuous definitions of reference systems for discrete networks with a non-permanent set of points and their realization through discrete time series of station coordinate functions and related earth rotation parameters.
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* Understanding the relation between such systems and reference systems implicitly introduced in theories of earth rotation and deformation.
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* Extension of ITRF establishment procedures beyond the current linear (constant velocity) model, treatment of periodic and discontinuous station position variations, understanding of their geophysical origins and related models.
 +
* Understanding the models used for data treatment within each particular technique, identification of possible biases and systematic effects and study of their influence on the combined ITRF solution. Study and improvement of current procedures for the merging of data from various space techniques.
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* Statistical aspects of reference frames, introduction and assessment of appropriate quality measures.
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* Problems of mathematical compatibility within current celestial-to-terrestrial datum transformations and proposal of new conventions which are data-based and theoretically compatible.
  
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* To realize the inventories of:
 
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** the available and applied methodologies for high-rate GNSS, in order to highlight their pros and cons and the open problems,
 
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** 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
 
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** 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 <br />
 
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with the by-product of establishing a standardized terminology
 
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* 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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* To address the new problems and future challanges arised from the inventories
 
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* 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
 
  
 
===Program of activities===
 
===Program of activities===
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* Launching of a web-page for dissemination of information, presentation, communication, outreach purposes, and providing a bibliography.
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* Working meetings at international symposia and presentation of research results in appropriate sessions.
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* Organization of workshops dedicated mainly to problem identification and motivation of relevant scientific research.
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* A special issue of the Journal of Geodesy on reference frames with papers from working group workshops and invited review papers.
  
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* To launch a questionnaire for the above mentioned inventory of methodologies, applications and technologies.
 
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* 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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* 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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* To organize a session at the forthcoming Hotine-Marussi symposium.
 
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* 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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===Members===
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===Membership===
  
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'' '''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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'' '''Athanasios Dermanis, (Greece, Chair)'''<br /> Zuheir Altamimi (France) <br /> Hermann Drewes (Germany) <br /> Fernando Sansò (Italy) <br /> Claude Boucher (France) <br /> Gerard Petit (France) <br /> Xavier Collilieux (France) <br /> Axel Nothnagel (Germany) <br /> Erricos Pavlis (USA) <br /> Jim Ray (USA) <br /> Frank Lemoine (USA) <br /> Geoff Blewitt (USA) <br /> Ludovico Biagi (Italy) <br /> Thomas Herring (USA) <br /> Pascal Willis (France) <br />''

Revision as of 14:27, 15 February 2010

Theory, implementation and quality assessment of geodetic reference frames

Chair: A. Dermanis (Greece)
Affiliation:Comm. 1, IERS

Introduction

The realization of a reference system by means of a reference frame, in the form of coordinate time series or coordinate functions for a global set of control stations is a complicated procedure. It involves input data from various space techniques each one based on its own advanced modelling and observation analysis techniques, as well as, criteria for the optimal selection of the time evolution of the reference frame among all data compatible possibilities. The relevant “observed” coordinate time series demonstrate significant signals of periodic, non- periodic variations and discontinuities, which pose the challenge of departing from the current ITRF model of linear time evolution, realized by reference epoch coordinates and constant velocities. The final product needs proper quality measures, which take also into account the possible modelling discrepancies, systematic errors and noise level of each particular space technique. The connection with a celestial frame by means of earth orientation parameters (EOPs) and current geophysical plate motion hypotheses necessitate the study of the compatibility of the geodetically established reference system with reference systems introduced in theoretical studies of the earth rotation and in theoretical geophysics. The working group is primarily aiming in problem identification, outlining of possible solution directions and motivation of relevant scientific research.

Objectives

  • Study of models for time-continuous definitions of reference systems for discrete networks with a non-permanent set of points and their realization through discrete time series of station coordinate functions and related earth rotation parameters.
  • Understanding the relation between such systems and reference systems implicitly introduced in theories of earth rotation and deformation.
  • Extension of ITRF establishment procedures beyond the current linear (constant velocity) model, treatment of periodic and discontinuous station position variations, understanding of their geophysical origins and related models.
  • Understanding the models used for data treatment within each particular technique, identification of possible biases and systematic effects and study of their influence on the combined ITRF solution. Study and improvement of current procedures for the merging of data from various space techniques.
  • Statistical aspects of reference frames, introduction and assessment of appropriate quality measures.
  • Problems of mathematical compatibility within current celestial-to-terrestrial datum transformations and proposal of new conventions which are data-based and theoretically compatible.


Program of activities

  • Launching of a web-page for dissemination of information, presentation, communication, outreach purposes, and providing a bibliography.
  • Working meetings at international symposia and presentation of research results in appropriate sessions.
  • Organization of workshops dedicated mainly to problem identification and motivation of relevant scientific research.
  • A special issue of the Journal of Geodesy on reference frames with papers from working group workshops and invited review papers.


Membership

Athanasios Dermanis, (Greece, Chair)
Zuheir Altamimi (France)
Hermann Drewes (Germany)
Fernando Sansò (Italy)
Claude Boucher (France)
Gerard Petit (France)
Xavier Collilieux (France)
Axel Nothnagel (Germany)
Erricos Pavlis (USA)
Jim Ray (USA)
Frank Lemoine (USA)
Geoff Blewitt (USA)
Ludovico Biagi (Italy)
Thomas Herring (USA)
Pascal Willis (France)

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