Colloque G2 2003 - Résumés


M. Amalvict (EOST)  
Absolute Gravity Measurements and Collocated Geodetic Positioning 
Techniques in Antarctica: a review. Implications for the polar cap

Due to the difficulty to reach Antarctic stations, only a few Absolute 
Gravity (AG) measurements have been performed in Antarctica. The first one 
was in the late 50s, using pendulum instrument while nowadays the FG5 
ballistic gravimeter is the most largely used. We make a review of these 
measurements, and present the different resulting values of gravity, 
including some repetitions.
For similar reasons, GPS data are restricted to permanent receivers 
installed at the permanent basis (remote stations are limited to austral 
summer time, since the solar panels are usable only during this period of 
the year). We present a review of available data and results.
Measurements of AG collocated with precise positioning systems are very 
useful in order to constrain the vertical displacement and consequently 
provide priceless information on the time evolution of the Antarctic polar 
cap. In particular, they will help separating the Post-Glacial Rebound 
(PGR) visco-elastic component from the elastic component due to present day 
ice melting.

J.-P. Barriot, M. Sarrailh, T. Fayard (BGI/UMR556)
Surveillance gravimétrique de la variation de la nappe phréatique
superficielle associée à la Garonne au niveau de Toulouse.

Nous présentons le réseau de surveillance gravimétrique de la
Garonne mis en place par le BGI dans la plaine fluviale de la Garonne au Sud
de la ville de Toulouse, ainsi que la méthodologie mise en oeuvre. Le but
ultime de ce réseau est de pouvoir corréler les observations piézométriques,
météorologiques et gravimétriques, afin d'établir le bilan de masse de la
nappe, et de pouvoir prédire son évolution à cours terme.