Difference between pages "JSG T.27" and "JSG T.30"

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(Created page with "<big>'''JSG 0.14: Fusion of multi-technique satellite geodetic data'''</big> Chair: ''Krsyzstof Sośnica (Poland)''<br> Affiliation: ''All Commissions and GGOS'' __TOC__ ==...")
 
(→‎Members)
 
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<big>'''JSG 0.14: Fusion of multi-technique satellite geodetic data'''</big>
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<big>'''JSG 0.17: Multi-GNSS theory and algorithms'''</big>
  
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Chair: ''Krsyzstof Sośnica (Poland)''<br>
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Chair: ''Amir Khodabandeh (Australia)''<br>
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Affiliation: ''All Commissions and GGOS''
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Affiliation:''Comm. 1, 4 and GGOS''
  
 
__TOC__
 
__TOC__
  
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===Terms of Reference===
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===Introduction===
  
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Observations provided by space geodetic techniques deliver a global picture of the changing system Earth, in particular temporal changes of the Earth’s gravity field, irregularities in the Earth rotation and variations of station positions due to various geodynamical phenomena. Different techniques are characterized by different accuracy and different sensitivity to geodetic parameters, e.g., GNSS provides most accurate pole coordinates, but cannot provide the absolute information on UT1-UTC, and thus, must be integrated with VLBI or LLR data. GRACE observations provide state-of-the-art and most accurate information on temporal changes of the gravity field, but the temporal changes of the Earth’s oblateness or the geocentre motion can be better determined using SLR data. Therefore, a fusion of various space geodetic observations is an indispensable prerequisite for a reliable description of the varying system Earth.
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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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However, the space geodetic observations are typically not free of artifacts related to deficiencies in various models used in the data reduction process. GNSS satellite orbits are very sensitive to deficiencies in solar radiation pressure modeling affecting, e.g., the accuracy of GNSS-derived Earth rotation parameters and geocentre coordinates. Deficiencies in modeling of antenna phase center offsets, albedo and the antenna thrust limit the reliability of GNSS and DORIS-derived scale of the terrestrial reference frame, despite a good global coverage of GNSS receivers and DORIS beacons. VLBI solutions are affected by an inhomogeneous quality delivered by different stations and antenna deformations. SLR technique is affected by the Blue-Sky effect which is related to the weather dependency of laser observations and the station-dependent satellite signature effect due to multiple reflections from many retroreflectors. Moreover, un-modeled horizontal gradients of the troposphere delay in SLR analyzes also limit the quality of SLR solutions. Finally, GRACE data are very sensitive to aliasing with diurnal and semidiurnal tides, whereas GOCE and Swarm orbits show a worse quality around the geomagnetic equator due to deficiencies in ionosphere delay modeling.
 
  
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Separation of real geophysical signals and artifacts in geodetic observations yield a very challenging objective. A fusion of different observational techniques of space geodesy may enhance our knowledge on systematic effects, improve the consistency between different observational techniques, and may help us to mitigate artifacts in the geodetic time series.
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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 mitigation of artifacts using parameters derived by a fusion of different techniques of space geodesy should comprise three steps: 1) identification of an artifact through an analysis of geodetic parameters derived from multiple techniques; 2) delivering a way to model an artifact; 3) applying the developed model to standard solutions by the analysis centers.
 
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Improving the consistency level through mitigating artifacts in space geodetic observations will bring us closer to fulfilling the objectives of the Global Geodetic Observing System (GGOS), i.e., the 1-mm accuracy of positions and 0.1-mm/year accuracy of the velocity determination. Without a deep knowledge of systematic effects in satellite geodetic data and without a proper modeling thereof, the accomplishment of the GGOS goals will never be possible.  
 
  
 
===Objectives===
 
===Objectives===
  
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* Developing of data fusion methods based on geodetic data from different sources
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The main objectives of this study group are:
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* Accuracy assessment and simulations of geodetic observations in order to fulfil GGOS’ goals
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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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* Study time series of geodetic parameters (geometry, gravity and rotation) and other derivative parameters (e.g., troposphere and ionosphere delays) determined using different techniques of space geodesy
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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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* Investigating biases and systematic effects in single techniques
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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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* Combination of satellite geodetic observations at the observation level and software synchronization
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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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* Investigating various methods of technique co-locations: through local ties, global ties, co-location in space
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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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* Identifying artifacts in time series of geodetic parameters using e.g., spatial, temporal, and spectral analyzes
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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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* Elaborating methods aimed at mitigating systematic effects and artifacts
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* to articulate the theoretical developments and findings through the journals and conference proceedings.
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* Determination of the statistical significance levels of the results obtained by techniques using different methods and algorithms
 
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* Comparison of different methods in order to point out their advantages and disadvantages
 
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* Recommendations for analysis working groups and conventions
 
  
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===Planned Activities===
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===Program of activities===
  
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* Preparing a web page with information concerning integration and consistency of satellite geodetic techniques and their integration with special emphasis on exchange of ideas, providing and updating bibliographic list of references of research results and relevant publications from different disciplines.
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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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* Working meetings at the international symposia and presentation of research results at the appropriate sessions.
 
  
 
===Members===
 
===Members===
  
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'' '''Krzysztof Sośnica (Poland), chair''' <br /> Toshimichi Otsubo (Japan) <br /> Daniela Thaller (Germany) <br /> Mathis Blossfeld (Germany) <br /> Andrea Maier (Switzerland) <br /> Claudia Flohrer (Germany) <br /> Agnieszka Wnek (Poland) <br /> Sara Bruni (Italy) <br /> Karina Wilgan (Poland) <br />''
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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 /> Thalia Nikolaidou (Canada) <br /> Robert Odolinski (New Zealand) <br />''

Revision as of 12:18, 14 March 2017

JSG 0.17: Multi-GNSS theory and algorithms

Chair: Amir Khodabandeh (Australia)
Affiliation:Comm. 1, 4 and GGOS

Introduction

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.

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.

Objectives

The main objectives of this study group are:

  • to identify and investigate challenges that are posed by processing and integrating the data of the next generation navigation and positioning satellite systems,
  • to develop new functional and stochastic models linking the multi-GNSS observations to the positioning and non-positioning parameters,
  • to derive optimal methods that are capable of handling the data-processing of large-scale networks of mixed-receiver types tracking multi-GNSS satellites,
  • 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,
  • 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,
  • to access the compatibility of the real-time multi-GNSS input parameters for positioning and non-positioning products,
  • to articulate the theoretical developments and findings through the journals and conference proceedings.

Program of activities

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.

Members

Amir Khodabandeh (Australia), chair
Peter J.G. Teunissen (Australia)
Pawel Wielgosz (Poland)
Bofeng Li (China)
Simon Banville (Canada)
Nobuaki Kubo (Japan)
Ali Reza Amiri-Simkooei (Iran)
Gabriele Giorgi (Germany)
Thalia Nikolaidou (Canada)
Robert Odolinski (New Zealand)

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