Abstract The determination of a precise geoid model still represents a chief demand for the geodetic communities worldwide. It necessitates the collection of as much as terrestrial gravity measurements with a homogenous distribution over a spatial region. The current research aims to collect several gravity datasets from several organizations and to unify their geodetic datums and gravity references. Such a task has been carried out within a geographic information systems (GIS) framework. A number of 9724 terrestrial gravity stations have been analyzed to construct a unique integrated gravimetric database of Egypt. That database has been referenced to the World Geodetic System 1984 (WGS84) and has been related to the Egyptian National Gravity Standardization Network 1997 (ENGSN-97) framework. GIS analysis tools have been performed to determine common points between gravity datasets and to construct correction surfaces to relate each category to the ENGSN-97 reference. Accordingly, an enhanced free-air gravity anomaly dataset has been developed. Such a modified gravimetric dataset is slightly more precise than the original one and performs a little better when compared to a global gravitational model (GGM). It has been found that the unification process performed herein has slightly enhanced the gravitational field of Egypt by almost 6.6%. Furthermore, comparing the terrestrial gravity data against the global GGM model shows that an improvement of 3.1% has been attained in terms of standard deviation. On another scene, the proposed approach might be valuable to the undergoing project for developing a precise geoid model of Egypt where different datasets have been collected from different sources with large variations with respect to geodetic datums and gravity references.

Abstract This study demonstrates that applying spatially variable density correction (VDC) to eliminate terrain effects in airborne gravity gradients enables the estimation of surface density distribution and improves the extraction of structural boundaries through a semi-automatic analysis. Because gravity gradients are more susceptible to nearby density anomalies than gravity, they are expected to have a high correspondence with rock-type distribution near the surface. In this study, airborne gravity gradients acquired using FALCON airborne gravity gradiometry system in the Yuzawa–Kurikoma area, Japan, were used to evaluate the validity of VDC. FALCON system measures only two horizontal components of the gradient tensor, which have anisotropic sensitivity to density anomalies. Hence, we derived the vertical gradients from these components and applied VDC. The estimated densities were generally consistent with the rock-type distribution shown in the geological map and with those obtained from actual rock samples. Subsequently, Euler deconvolution, a semiautomatic analysis technique, was conducted on the VDC-corrected data to extract lineaments based on the continuity of the solutions. The extracted structures agreed well with previously identified or inferred faults, and several new lineaments were found along the extensions of these faults. Additionally, deconvolution was applied to the data after terrain correction with a unique assumed density, and the variability and structural characteristics of the solution distributions were compared between the two correction methods based on information entropy. The VDC-corrected data yielded lower entropy than the conventionally corrected data, indicating that VDC can improve the detectability of structural boundaries when using Euler deconvolution.