HR: 16:15h
AN: G34A-02    [Abstracts]
TI: Estimating Geocenter motions from GPS measurements
AU: * Lavall\'{e}e, D A
EM: d.a.lavallee@ncl.ac.uk
AF: School of Civil Engineering and Geosciences, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU United Kingdom
AU: van Dam, T
EM: tvd@ecgs.lu
AF: European Center for Geodynamics and Seismology, Rue Josy Welter, 19, Walferdange, L-7256 Luxembourg
AU: Blewitt, G
EM: gblewitt@unr.edu
AF: Nevada Bureau of Mines and Geology, and Seismological Laboratory, University of Nevada, Reno Mail stop 178, Reno, NV 89557-0088 United States
AU: Clarke, P J
EM: peter.clarke@ncl.ac.uk
AF: School of Civil Engineering and Geosciences, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU United Kingdom
AB: Change in the displacement vector between the Center of Mass (CM) of the Earth system and the Center of the Earth's geometrical Figure (CF) is the most common geocenter motion observed using modern geodetic techniques. Primarily this is due to the location on the Earth's surface of the various satellite tracking networks (DORIS, GPS, SLR, VLBI). Observations of this geocenter motion are fundamental to defining the origin of the International Terrestrial Reference Frame (ITRF) and investigating the surface mass transport between oceans, continent and atmosphere which cause this motion. Estimates of this geocenter motion have been at various levels of agreement both between and within different geodetic techniques. Cross-technique differences can partly be put down to the broad spectrum of technique specific errors but much of the difference lies in the use of different surface tracking networks. What is required is a robust method that is relatively unaffected by the network used to sample the Earth's surface figure and hence CF. With this in mind we explore the different estimation techniques which might be used to estimate the geocenter and investigate the performance for GPS data. We compare and contrast different estimation methods using 7 years of fiducial-free GPS solutions from the IGS Analysis centers each of which use different software and tracking networks. Finally we discuss the implications for the interpretation of geocenter estimates and definition of the ITRF.
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
DE: 1247 Terrestrial reference systems
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting