الفهرس 
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Abstract
High-quality gravity data are crucial for accurate geoid determination, hence
allowing for precise height determination. Accurate gravity measurements are
considered the primary input for geoid determination. However, unifying,
filtering, and improving the observations are essential tasks before predicting a new surface for any area. Additionally, obtaining high-resolution Global Gravity Models (GGMs) typically involves a complex process that integrates
various data sources like Satellite Missions, Terrestrial Measurements,
Satellite Altimetry, Airborne, and Marine gravity data. In this study, the combination of recent GGM and the terrestrial observations
for the area of interest (Egypt) was presented using four steps. In the beginning,
terrestrial gravity data in Egypt have been collected by several companies and
organizations over many decades using different datums, so these
measurements need to be unified before using them for any operations. For
instance, three related datasets (NGSBN77, Dataset3, Dataset5) on the old
Egyptian datum (OED) are transformed to be in the world Geodetic system
(WGS84). Secondly, removing the odd values that were discovered while
comparing the free air gravity anomaly of the terrestrial data with the
corresponding GGM value.
Furthermore, a GGM was adopted based on the evaluation of four different
GGMs to choose the best representative model for the area using terrestrial
data. Thirdly, improving the adopted GGM using trustable terrestrial gravity
data. However, shifting the model to the terrestrial data by using accurate
points makes a remarkable improvement. Finally, a multi-linear regression
model was obtained to predict geoidal undulation values from their
corresponding free air gravity anomalies of the reliable terrestrial data.
The results showed that (SGG UGM 2) is one of the best mod representing the gravity field in Egypt. The available different data sets are
unified to WGS84, and a list of consistent terrestrial gravity values is obtained. Additionally, gravity anomalies were normalized by replacing the normal gravity on OED with its corresponding value on WGS 84, ensuring accurate and consistent computation of gravity anomalies.
Moreover, the results also indicated that geoidal undulations can be predicted from free air gravity anomalies using a simple linear regression model with
enough precision for many applications. Consequently, a road map is
suggested in the study for utilizing the existing terrestrial gravity
measurements instead of making new money-cost, time-consuming, and
tedious measurements.