Difference between revisions of "JSG T.32"

From Icctwiki
Jump to: navigation, search
(Created page with "<big>'''JSG 0.19: High resolution harmonic analysis and synthesis of potential fields'''</big> Chair: ''Sten Claessens (Australia)''<br> Affiliation:''Comm. 2 and GGOS'' __T...")
 
 
(3 intermediate revisions by 2 users not shown)
Line 1: Line 1:
−
<big>'''JSG 0.19: High resolution harmonic analysis and synthesis of potential fields'''</big>
+
<big>'''JSG T.32: High-rate GNSS for geoscience and mobility'''</big>
  
−
Chair: ''Sten Claessens (Australia)''<br>
+
Chair: ''Mattia Crespi (Italy)''<br>
−
Affiliation:''Comm. 2 and GGOS''
+
Affiliation:''Commissions 1, 3 and 4, GGOS''
  
 
__TOC__
 
__TOC__
  
−
===Terms of Reference===
+
===Introduction===
  
−
The gravitational fields of the Earth and other celestial bodies in the Solar System are customarily represented by a series of spherical harmonic coefficients. The models made up of these harmonic coefficients are used widely in a large range of applications within geodesy. In addition, spherical harmonics are now used in many other areas of science such as geomagnetism, particle physics, planetary geophysics, biochemistry and computer graphics, but one of the first applications of spherical harmonics was related to the gravitational potential, and geodesists are still at the forefront of research into spherical harmonics. This holds true especially when it comes to the extension of spherical harmonic series to ever higher degree and order (d/o).
+
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.
−
The maximum d/o of spherical harmonic series of the Earth’s gravitational potential has risen steadily over the past decades. The highest d/o models currently listed by the International Centre for Global Earth Models (ICGEM) have a maximum d/o of 2190. In recent years, spherical harmonic models of the topography and topographic potential to d/o 10,800 have been computed, and with ever-increasing computational prowess, expansions to even higher d/o are feasible. For comparison, the current highest-resolution global gravity model has a resolution of 7.2” in the space domain, which is roughly equivalent to d/o 90,000 in the frequency domain, while the highest-resolution global Digital Elevation Model has a resolution of 5 m, equivalent to d/o ~4,000,000.
 
  
−
The increasing maximum d/o of harmonic models has posed and continues to pose both theoretical and practical challenges for the geodetic community. For example, the computation of associated Legendre functions of the first kind, which are required for spherical harmonic analysis and synthesis, is traditionally subject to numerical instabilities and underflow/overflow problems. Much progress has been made on this issue by selection of suitable recurrence relations, summation strategies, and use of extended range arithmetic, but further improvements to efficiency may still be achieved.  
+
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 additional primary goals were, obviously, to get this information with the highest accuracy and in the shortest time.  
  
−
There are further separate challenges in ultra-high d/o harmonic analysis (the forward harmonic transform) and synthesis (the inverse harmonic transform). Many methods for the forward harmonic transform exist, typically separated into least-squares and quadrature methods, and further comparison between the two at high d/o, including studying the influence of aliasing, is of interest. The inverse harmonic transform, including synthesis of a large variety of quantities, has received much interest in recent years. In moving towards higher d/o series, highly efficient algorithms for synthesis on irregular surfaces and/or in scattered point locations, are of utmost importance.  
+
The advances in technology and the deployment of new constellations, after GPS (in the next few years the European Galileo, the Chinese Beidou and the Japanese QZSS will be completed) 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.
  
−
Another question that has occupied geodesists for many decades is whether there is a substantial benefit to the use of oblate ellipsoidal (or spheroidal) harmonics instead of spherical harmonics.  The limitations of the spherical harmonic series for use on or near the Earth’s surface are becoming more and more apparent as the maximum d/o of the harmonic series increase. There are still open questions about the divergence effect and the amplification of the omission error in spherical and spheroidal harmonic series inside the Brillouin surface.  
+
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.
  
−
The Hotine-Jekeli transformation between spherical and spheroidal harmonic coefficients has proven very useful, in particular for spherical harmonic analysis of data on a reference ellipsoid. It has recently been improved upon and extended, while alternatives using surface spherical harmonics have also been proposed, but the performance of the transformations at very high d/o may be improved further. Direct use of spheroidal harmonic series requires (ratios of) associated Legendre functions of the second kind, and their stable and efficient computation is also of ongoing interest.
+
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 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.
 +
 
 +
Further, due to the contemporary technological development of other sensors (hereafter referred as ancillary sensors) related to positioning and kinematics able to collect high-rate data (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 opens, again, new opportunities and problems, first of all related to sensors integration.
 +
In this respect, Android based mass-market devices (smartphones and tablets) are nowadays able to provide 1 Hz raw GNSS measurements (with a growing number of models able to provide multi-constellation and multi-frequency code and phase observations) in addition to the above-mentioned ancillary sensors measurements.
 +
 
 +
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===
 
===Objectives===
  
−
The objectives of this study group are to:
+
* To realize the inventories of:
−
* Create and compare stable and efficient methods for computation of ultra-high degree and order associated Legendre functions of the first and second kind (or ratios thereof), plus its derivatives and integrals.
+
** the available and applied methodologies for high-rate GNSS, in order to highlight their pros and cons and the open problems
−
* Study the divergence effect of ultra-high degree spherical and spheroidal harmonic series inside the Brillouin sphere/spheroid.
+
** 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
−
* Verify the numerical performance of transformations between spherical and spheroidal harmonic coefficients to ultra-high degree and order.
+
** 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 modelling with the by-product of establishing a standardized terminology.
−
* Compare least-squares and quadrature approaches to very high-degree and order spherical and spheroidal harmonic analysis.
+
* 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; outlier detection and removal; issues about GNSS constellations interoperability; ancillary sensors evaluation, cross-calibration and integration.
−
* Study efficient methods for ultra-high degree and order harmonic analysis (the forward harmonic transform) for a variety of data types and boundary surfaces.
+
* To address new problems and future challenges which arise from inventories.  
−
* Study efficient methods for ultra-high degree and order harmonic synthesis (the inverse harmonic transform) of point values and area means of all potential quantities of interest on regular and irregular surfaces.
+
* To investigate about the interaction with present real-time global (IGS-RT, 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===
  
−
* Providing a platform for increased cooperation between group members, facilitating and encouraging exchange of ideas and research results.
+
* To launch a questionnaire for the above mentioned inventory of methodologies, applications and technologies.
−
* Creating and updating a bibliographic list of relevant publications from both the geodetic community as well as other disciplines for the perusal of group members.
+
* 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, raw relevant datasets, provision and updating bibliographic list of references of research results and relevant publications from different disciplines.
−
* Organizing working meetings at international symposia and presenting research results in the appropriate sessions.
+
* 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 JSG members.
 +
* To promote sessions and presentation of research results at international symposia both related to Earth science (IAG/IUGG, EGU, AGU, EUREF, IGS), engineering (workshops and congresses in structural, geotechnical, mechanical, transport and automotive engineering), and life sciences (sports and health care).
  
 
===Membership===
 
===Membership===
  
−
'' '''Sten Claessens (Australia), chair''' <br /> Hussein Abd-Elmotaal (Egypt) <br /> Oleh Abrykosov (Germany) <br /> Blažej Bucha (Slovakia) <br /> Toshio Fukushima (Japan) <br /> Thomas Grombein (Germany) <br /> Christian Gruber (Germany) <br /> Eliška Hamáčková (Czech Republic) <br /> Christian Hirt (Germany) <br /> Christopher Jekeli (USA) <br /> Otakar Nesvadba (Czech Republic) <br /> Moritz Rexer (Germany) <br /> Josef Sebera (Czech Republic) <br /> Kurt Seitz (Germany) <br />''
+
'' '''Mattia Crespi (Italy), chair ''' <br /> Elisa Benedetti (United Kingdom) <br /> Mara Branzanti (Switzerland) <br /> Liang Chen (China) <br /> Gabriele Colosimo (Switzerland) <br /> Elisabetta D’Anastasio (New Zealand) <br /> Roberto Devoti (Italy) <br /> Rui Fernandes (Portugal) <br /> Marco Fortunato (Italy) <br /> Athanassios Ganas (Greece) <br /> Pan Li (Germany) <br /> Alain Geiger (Switzerland) <br /> Jianghui Geng (China) <br /> Dara Goldberg (USA) <br /> Kathleen Hodgkinson (USA) <br /> Shuanggen Jin (China) <br />  Iwona Kudlacik (Poland) <br /> Jan Kaplon (Poland) <br /> Augusto Mazzoni (Italy) <br /> Joao Francisco Galera Monico (Brazil) <br /> Héctor Mora Páez (Colombia) <br /> Michela Ravanelli (Italy) <br /> Giorgio Savastano (Luxembourg) <br /> Sebastian Riquelme (Chile) <br /> Peiliang Xu (Japan) <br />''

Latest revision as of 12:33, 10 June 2020

JSG T.32: High-rate GNSS for geoscience and mobility

Chair: Mattia Crespi (Italy)
Affiliation:Commissions 1, 3 and 4, GGOS

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.

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 additional primary goals were, obviously, to get this information with the highest accuracy and in the shortest time.

The advances in technology and the deployment of new constellations, after GPS (in the next few years the European Galileo, the Chinese Beidou and the Japanese QZSS will be completed) 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.

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.

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 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.

Further, due to the contemporary technological development of other sensors (hereafter referred as ancillary sensors) related to positioning and kinematics able to collect high-rate data (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 opens, again, new opportunities and problems, first of all related to sensors integration. In this respect, Android based mass-market devices (smartphones and tablets) are nowadays able to provide 1 Hz raw GNSS measurements (with a growing number of models able to provide multi-constellation and multi-frequency code and phase observations) in addition to the above-mentioned ancillary sensors measurements.

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:
    • the available and applied methodologies for high-rate GNSS, in order to highlight their pros and cons and the open problems
    • 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
    • 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 modelling with the by-product of establishing a standardized terminology.
  • 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; outlier detection and removal; issues about GNSS constellations interoperability; ancillary sensors evaluation, cross-calibration and integration.
  • To address new problems and future challenges which arise from inventories.
  • To investigate about the interaction with present real-time global (IGS-RT, 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

  • To launch a questionnaire for the above mentioned inventory of methodologies, applications and technologies.
  • 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, raw relevant datasets, provision and updating bibliographic list of references of research results and relevant publications from different disciplines.
  • 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 JSG members.
  • To promote sessions and presentation of research results at international symposia both related to Earth science (IAG/IUGG, EGU, AGU, EUREF, IGS), engineering (workshops and congresses in structural, geotechnical, mechanical, transport and automotive engineering), and life sciences (sports and health care).

Membership

Mattia Crespi (Italy), chair
Elisa Benedetti (United Kingdom)
Mara Branzanti (Switzerland)
Liang Chen (China)
Gabriele Colosimo (Switzerland)
Elisabetta D’Anastasio (New Zealand)
Roberto Devoti (Italy)
Rui Fernandes (Portugal)
Marco Fortunato (Italy)
Athanassios Ganas (Greece)
Pan Li (Germany)
Alain Geiger (Switzerland)
Jianghui Geng (China)
Dara Goldberg (USA)
Kathleen Hodgkinson (USA)
Shuanggen Jin (China)
Iwona Kudlacik (Poland)
Jan Kaplon (Poland)
Augusto Mazzoni (Italy)
Joao Francisco Galera Monico (Brazil)
Héctor Mora Páez (Colombia)
Michela Ravanelli (Italy)
Giorgio Savastano (Luxembourg)
Sebastian Riquelme (Chile)
Peiliang Xu (Japan)

Retrieved from "http://icct.kma.zcu.cz/index.php?title=JSG_T.32&oldid=597"