XGM2019e is a combined global gravity field model represented through
spheroidal harmonics up to d/o 5399, corresponding to a spatial
resolution of 2’ (~4 km). As data sources it includes the satellite
model GOCO06s in the longer wavelength area combined with terrestrial
measurements for the shorter wavelengths. The terrestrial data itself
consists over land and ocean of gravity anomalies provided by courtesy
of NGA (identical to XGM2016, having a resolution of 15’) augmented with
topographically derived gravity over land (EARTH2014). Over the oceans,
gravity anomalies derived from satellite altimetry are used (DTU13, in
consistency with the NGA dataset).
The combination of the satellite data with the terrestrial observations
is performed by using full normal equations up to d/o 719 (15’).
Beyond d/o 719, a block-diagonal least-squares solution is calculated
for the high-resolution terrestrial data (from topography and
altimetry). All calculations are performed in the spheroidal harmonic
domain.
In the spectral band up to d/o 719 the new model shows over land a
slightly improved behavior over preceding models such as XGM2016,
EIGEN6c4 or EGM2008 when comparing it to independent GPS leveling data.
Over land and in the spectral range above d/o 719 the accuracy of
XGM2019e slightly suffers from the sole use oftopographic forward
modelling; Hence, errors are increased in well-surveyed areas compared
to models containing real gravity data, e.g. EIGEN6c4 or EGM2008.
However, the performance of XGM2019e can be considered as globally more
homogeneous and independent from existing high resolution global models.
Over the oceans the model exhibits an improved performance throughout
the complete spectrum (equal or better than preceding models).
