  The high accuracy now reached in the VLBI Earth Orientation Parameters (EOP)
determination requires looking further at the various geophysical contributions
to variations in EOP. The determination of the Earth gravity field from space
geodetic techniques now allows us to obtain the temporal variations of the low
degree coefficients of the geopotential, combining the treatment of different
satellites (e.g. Lageos1, Lageos2, Starlette ...). We present a new computation
of the degree 2 coefficients of the variable Earth gravity field. This study is
based upon the using of (i) new orbit standards, (ii) the GRACE mean gravity
field and (iii) Lageos1 data from 1985 until 2004 (merged with Lageos2 data
from 1993). These temporal variations of the Earth gravity field can be related
to the Earth Orientation Parameters through the inertia tensor. This paper
shows these relations and discusses how such geodetic data can contribute to
the understanding of the variations in EOP. This paper also studies if these
refined 20-yr of Lageos data can give us refined value of the 18.6-yr tidal
term, as well as of the secular drift of the C20 geopotential coefficient.
