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Terms of
Reference
Up to now the operating satellite navigation systems GPS
and GLONASS allow a huge user community easy access to reference frames very
close to the most recent realization of the ITRS. The IAG Services, International
Earth Rotation and Reference Systems Service (IERS) and the International
GPS Service (IGS), provide the necessary products to tie these frames to the
International Terrestrial Reference Frame (ITRF), which is based upon a set
of estimated coordinates and velocities of stable stations observed by all
space techniques. The design of the upcoming GALILEO system - its envisaged
accuracy and the long-term stability - implies that also GALILEO will become
a highly valuable technique for the definition and maintenance of the ITRF.
The modernization of GPS and the completion of the GLONASS system will further
improve the situation. The goal of Study Group 1.2 is to evaluate and support
the use of Global Navigation Satellite Systems (GNSS) for the definition and
densification of the ITRF.
Steering
Committee
Robert
Weber (Tech. Univ. of Vienna, Austria)
- Chair
Objectives
- Document the potential contributions of GNSS to reference frame establishment
and maintenance.
- Investigate the ties and their time evolution between GNSS Broadcast
Frames like WGS84, PZ-90, and the upcoming GALILEO Reference Frame, and
the ITRF.
- Examine deficiencies in the stability of the global GNSS station network,
especially focussing on stations contributing to the ITRF2000 catalogue.
- Prepare a consolidated feedback concerning GPS, GLONASS and GALILEO
frame establishment and improvement based on relevant experience in areas
such as receiver site selection, installation and maintenance.
- Investigate the individual strengths and shortcomings of GPS, GLONASS
and GALILEO for Reference System Realisation and work out synergies.
- Study the ties of regional and local frames realized by a permanently
increasing number of active real-time GNSS networks.
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