| 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 several datums, so these measurements need to be unified before using them for any operations. For instance, three related datasets (NGSBN77, Dataset3, Dataset5) to the old Egyptian datum (OED) are transformed to be in the world Geodetic system (WGS84).
Secondly, removing unwanted components that were discovered while
comparing the free air gravity anomaly of the terrestrial data with the
corresponding GGM value. Furthermore, the 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 selected 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. Based on the procedures and results, a new strategy is suggested for utilizing the existing terrestrial gravity measurements instead of making new money-cost, time-consuming, and tedious measurements. |
