EIGEN-6C4 is a static global combined gravity field model up to degree and order 2190.
It has been elaborated jointly by GFZ Potsdam and GRGS Toulouse.
The combination of the different satellite and surface data sets has been
done by a band-limited combination of normale equations (to max degree 370),
which are gererated from observation equations for the spherical harmonic
coefficients. A brief description of the applied techniques for the generation
of such a combined gravity field model is given in Shako et al. 2014. The
resulted solution to degree/order 370 has been extended to degree/order 2190 by
a block diagonal solution using the DTU10 global gravity anomaly data grid.
Input Data:- LAGEOS (deg. 2 - 30): 1985 - 2010- GRACE RL03 GRGS (deg. 2 - 130): ten years 2003 - 2012- GOCE-SGG data, processed by the direct approach (Pail et al. 2011,
Bruinsma et al. 2014, to deg. 235) incl. the gravity gradient
components Txx, Tyy, Tzz and Txz out of the following time spans:
837 days out of the nominal mission time span 20091101 - 20120801
422 days out of the lower orbit phase between 20120901 - 20130524
The GOCE polar gaps were stabilized by the Spherical Cap Regularization
(Metzler and Pail 2005) using the combined gravity field model EIGEN-6C3stat- Terrestrial data (max degree 370):
DTU12 ocean geoid data (Anderson et al. 2009) and an EGM2008 geoid height
grid for the continents
