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DORISMail               02-Dec-2004 14:36:58                   Message No 0358
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Author: Jim Ray "(NGS" 301-713-2850 "x112)" <jimr@ngs.noaa.gov
Subject: Reference System session at EGU2005 

Author: Jim Ray, Ernst Schrama, & Zuheir Altamimi

   EGU 2nd General Assembly -- Vienna, Austria, 25-29 April 2005
             http://www.copernicus.org/EGU/ga/egu05/

Dear Colleagues,

The 2nd General Assembly of the European Geosciences Union will be held in
Vienna, Austria, 25-29 April 2005.  We draw your attention in particular to
session "G1 - Reference System Stability, Accuracy, and the Presence of
Secular or Seasonal Signals", which is co-sponsored by Hydrological and
Cryospheric Sciences.  This session should provide a good opportunity to
prepare for the new ITRF2004 realization, among other things.

  As geodetic applications in the Earth sciences advance in their
  capabilities and accuracy goals, the demands placed on the International
  Terrestrial Reference Frame (ITRF) increase also since this is the
  fundamental platform from which most large-scale measurements are made.
  The basic ITRF requirements concern: accuracy in terms of origin and
  scale; precision in terms of relative internal consistency of station
  positions and velocities; long-term stability of origin, scale, and
  orientation; universal and easy user access.

  ITRF is formed by a combination of different space geodetic techniques.
  Since no one technique possesses all the needed strengths, a major
  challenge is to detect and mitigate systematic errors from the
  individual techniques optimally. Stability is particularly important for
  such problems as reliable detection of e.g. sea-level change, which
  requires scale rate uncertainties <0.1 ppb/yr. It is difficult to
  objectively assess whether this level is actually being attained or not
  because there is minimal internal redundancy, especially for origin and
  scale.

  The presence of non-linear (non-tidal) variations in station motions
  complicates ITRF maintenance. On the one hand, these can provide
  valuable geophysical insights, for example into large-scale fluid mass
  movements or aspects of global change or post-seismic deformation. Full
  geophysical utilization requires separating complicating effects such as
  highly localized motions like subsidence, or effects caused by long
  wavelength GPS orbit errors, propagation correction errors, antenna
  model limitations, multipath and other environmental effects, etc.
 
  This session will focus on updating user requirements for the ITRF and
  examining its current capabilities and limitations. Any inputs that
  might aid in improving the next ITRF realization and studies of the ITRF
  accuracy or stability using independent methods are welcome. 


Important Dates:
07 January  2005:  Deadline for support applications
21 January  2005:  Deadline for receipt of abstracts
08 April 2005:     Deadline for pre-registration & hotel booking

Please consider submitting a paper to this symposium or contact us
directly if you have any questions.

Sincerely,

Jim Ray, jimr@ngs.noaa.gov
Geosciences Research Division, National Geodetic Survey

Ernst Schrama, e.j.o.schrama@lr.tudelft.nl
Department of Geodesy, Technical Univ. of Delft

Zuheir Altamimi, altamimi@ensg.ign.fr
ENSG/LAREG, Institut Geographique National




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