A gravimetric geoid was predicted for the newly developed Toshka sector in South Egypt.
The Least-Squares collocation solution utilized scattered heterogeneous data types as input,
using the remove-Restore technique. The input data included gravity anomalies, gravity
disturbances and vertical deflection components, while the available GPS/Lev. geoidal height
data were devoted for the evaluation of the gravimetric geoid accuracy. The dominant data
type was the gravity disturbances, and hence, this data was used to predict the empirical
covariance function. The RTM topographic effect was accounted for, using an appropriate
DTM for the area under investigation. The long wavelength contribution was properly
accounted for, using the locally fitted geopotential model EGM96EGCT. The results show
that the mean collocation standard error is about 5 cm, while the comparison at the
independent GPS/Lev. check points gives an external accuracy of about 16 cm. Based on the
obtained results, the obtained Toshka geoid is recommended to be used for any future
geodetic computations in that area. It is also recommended to be used for densifying leveling
networks of lower order. Consequently, appropriate future planning for rigorous GPS
measurements in these areas is highly recommended. |
