TITLE:
On the Accuracy Assessment of the Latest Releases of GOCE Satellite-Based Geopotential Models with EGM2008 and Terrestrial GPS/Levelling and Gravity Data over Egypt
AUTHORS:
Mohamed El-Ashquer, Basem Elsaka, Gamal El-Fiky
KEYWORDS:
GOCE-Based GGMs, Free-Air Gravity Anomalies, GPS/Levelling Data, Spectral Enhancement Method (SEM)
JOURNAL NAME:
International Journal of Geosciences,
Vol.7 No.11,
November
29,
2016
ABSTRACT: The Global Geopotential
Models (GGMs) of GOCE (Gravity Recovery and steady- state Ocean Circulation Explorer) differ globally as
well as regionally in their accuracy and resolution based on the maximum degree
and order (d/o) of the fully normalized spherical harmonic (SH) coefficients, which express each GGM. The main idea of this study is to
compare the free-air gravity anomalies and quasi geoid heights determined from
several recent GOCE-based GGMs with the corresponding ones from the Earth
Gravitational Model 2008 (EGM2008) over Egypt on the one hand and with
ground-based measurements on the other hand. The results regarding to the
comparison of GOCE-based GGMs with terrestrial gravity and GPS/levelling data
provide better improvement with respect to EGM2008. The 4th release GOCE-based
GGM developed with the use of space-wise solution strategy (SPW_R4)
approximates the gravity field well over the Egyptian region. The SPW_R4 model
is accordingly suggested as a reference model for recovering the long
wavelength (up to SH d/o 200) components of quasi geoid heights when modelling
the gravimetric quasi-geoid over the Egypt. Finally, three types of
transformation models: Four-,
Five- and Seven-parameter transformations have been applied to reduce the data
biases and to provide a better fitting of quasi geoid heights obtained from the
studied GOCE-based GGMs to those from GPS/levelling data. These models reveal
that the standard deviation of vertical datum over Egypt is at the level of
about 32 cm.