Recently, several high and ultra-high degree global harmonic models have been developed. In what follows, An assessment and
enhancement of newly Erath Geopotential Models “EGMs” which released between 2015, up to 2017 were done, including corporate data from the
gravity satellites CHAllenging Minisatellite Payload “CHAMP”, Gravity Recovery and Climate Experiment “GRACE” and The Gravity field and steadystate Ocean Circulation Explorer Mission “GOCE" dedicated satellite gravimetric mission, with terrestrial gravity anomalies data over the whole area of
Egypt. The gravity anomalies which are implied by the models compared with free air gravity anomalies observations while the geoid heights which are
implied by the Models compared with discrete geometrical heights from co-located GPS and sprit-leveling. Second step utilize the available
GPS/leveling data at discrete points to enhancement the chosen EGMs according to its acting performance “from the first step” all over Egypt territory.
The aim of this paper is to improve our knowledge about the performance of the satellite only tracking and combination EGMs which are generated from
various satellites or only tracking "CHAMP, GRACE and GOCE" in addition to utilized the available terrestrial data over the Whole area of Egypt to
enhance the performance of the chosen EGM from the evaluation step.
The assessment results of the comparison among the different geopotential model with the land gravity data “free air gravity anomalies and
GPSLeveling at discrete points” under investigation in this study have indicated the outstanding performance of EGM [XGM2016] to the other examined
GGMs.
EGM [XGM2016] has superior performance with smallest [RMSE] is [20.595 mgal] with respect to [w.r.t] gravity anomaly and [0.577 m] w.r.t geoidal
height. An enhancement of EGM [XGM2016] with the GPSLeveling discrete data points, clarify that the model is enhanced by 2.6% “with using only 80
GPS/leveling data points with bad distribution” than the original one, while the internal accuracy reached to be 44 cm in terms of [R.M.S.E] and 19 cm in
terms of stander deviation as shown in table [8] and the external accuracy enhanced by 28%.
Fortunately if there is enough terrestrial data with good distribution over the whole territory this ratio defiantly will be increase. |
