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IERS Message No. 81                                     January 11, 2006
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EGU 2006 - Session G4: "Interactions between the three pillars of space 
geodesy: surface geometry, Earth rotation and gravity field"


Dear Colleagues,

we would like to draw your attention to session G4

"Interactions between the three pillars of space geodesy: surface
geometry, Earth rotation and gravity field"

at the EGU General Assembly to be held in Vienna, Austria, 
April 2-7, 2006.

The topic of session G4 has to be seen in the context of the Global 
Geodetic Observing System (GGOS) project of the IAG. It tries to cover 
the scientific issues concerning the integration of the space geodetic
techniques.

The deadline for the submission of abstracts is January 13, 2006, for
online submission (January 9, 2006, else).
Further information is available at the web site of the conference:

http://meetings.copernicus.org/egu2006/

We are looking forward to your contribution to this challenging
and interesting topic.

With best regards,

Markus Rothacher, Hermann Drewes
Conveners Session G4


Description of Session G4:

Interactions between the three pillars of space geodesy: surface
geometry, Earth rotation and gravity field
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At the IAG Scientific Assembly in Cairns in Summer 2005 the Global 
Geodetic Observing System (GGOS), a project of the IAG entered its 
operational phase. One of the goals of GGOS is the integration of the 
three pillars of geodesy, namely the Earth's shape (including the 
oceans), Earth rotation and the Earth's gravity field, as well as their
temporal variations. The topic of this session are all the relationships
and interactions between these three pillars. Contributions are welcome
from purely theoretical and/or modelling considerations to observational
evidence of the relationships derived from the space geodetic techniques
including VLBI, SLR, DORIS, GNSS, the altimetry and gravity missions, 
and data on the global geophysical fluids. We also encourage 
contributions showing results based on a combined and consistent 
estimation of parameters from all three pillars. The consistent 
modelling of all three (or at least two of the three) pillars in a 
physical sense and the setup of common standards for the geometrical as
well as the gravimetrical component, should also be considered in such 
an integration process and belong to the scope of this session.
Examples of interesting relationships are, e.g., reference frame origin 
and orientation, the low-degree gravity field coefficients (C01, S11, 
C11, S21, C21, and S22), and the position and orientation of the Earth's
figure and rotation axes; loading effects seen as surface deformation, 
gravity field changes and Earth rotation variations; global mass 
transport, conservation of mass and angular momentum; connections 
between "wind" and "matter" terms derived from Earth rotation, gravity 
field variations and surface deformation; variations in polar motion and
length of day related to changes of the changes of the Earth's inertia
tensor and J2 (e.g., from SLR or CHAMP/GRACE); etc.


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