Long wavelength Earth gravity field series from satellite tracking, altimeter and surface data, spherical harmonic representation

GRIM4-C global gravity field models are based on the analysis of satellite
orbit perturbations, evaluating optical, doppler and laser tracking data of
about 30 satellites, combined with 1degx1deg gravity anomaly data sets
completed by geoid undulations over the oceans derived from satellites
altimetry or by directly evaluating altimeter data. The models are given as a
set of fully normalized spherical harmonic coefficients complete to degree and
order 50 and 60 (GRIM4-C3, GRIM4-C3T), respectively. The first solution
GRIM4-C1 includes data from 27 satellites, 1degx1deg gravity anomalies (OSU 89)
and 1degx1deg SEASAT geoid undulations (March 89); GRIM4-C2 (29 satellites),
GRIM4-C3 (30 satellites, OSU 91 gravity anomalies, GEOS3/SEASAT/GEOSAT geoid
undulations) , and GRIM4-C4 (32 satellites, OSU 91 plus selected gravity
anomalies, ERS geoid undulations) are improved solutions. GRIM4-C3T is taken
form a joint gravity, sea surface topography solution with 18d-GEOSAT file.