Comparative analysis of free-air gravity anomalies in global models of Earth
Students Name: Stekha Andrii
Qualification Level: magister
Speciality: Space Geodesy
Institute: Institute of Geodesy
Mode of Study: full
Academic Year: 2024-2025 н.р.
Language of Defence: ukrainian
Abstract: Free-air gravity anomalies are an essential characteristic for evaluating the Earth’s gravitational field, widely used in geodesy, gravimetry, and other geosciences. Such anomalies are defined as the difference between measured gravity values and conditionally “normal” values corresponding to the gravitational field on a theoretical, smooth Earth surface. Free-air gravity anomalies are calculated at an elevation above the ellipsoid, allowing consideration of the influence of terrain and geological features of the study area, serving as a key indicator of local gravitational field variations caused by the distribution of mass within the Earth’s crust and mantle. Analyzing free-air gravity anomalies is a fundamental step for identifying deviations in the gravitational field that are not accounted for by global models. Comparison of free-air gravity anomalies with data from global models allows assessment of the accuracy and level of detail in models such as WGM2012, EGM2008, EIGEN-6C4, GECO, XGM2019e2159, and SGG UGM2. Each of these models differs in data processing methods that combine satellite measurements, terrestrial gravimetric observations, and modeling, which consider various aspects of gravitational influence. Global gravitational field models are used for precise geodetic measurements, Earth surface monitoring, geophysical and geological research, and modeling gravitational field changes due to major natural events. Comparing models is an important step in selecting the most appropriate one for a specific task. Differences in calculation algorithms and data structure highlight the need for detailed analysis of these models, facilitating optimal accuracy in addressing local and global geoscience tasks. This study focuses on a systematic comparative analysis of free-air gravity anomalies calculated based on various global Earth models. Specifically, the research includes: 1) studying the theoretical foundations of free-air gravity anomaly formation; 2) comparing gravity anomalies determined by the WGM2012, EGM2008, EIGEN-6C4, GECO, XGM2019e2159, and SGG UGM2 models; 3) assessing the accuracy of gravity anomalies and identifying optimal conditions for the application of specific models. The results obtained allow for a detailed identification of the characteristics of free-air gravity anomalies for each selected model, essential for analyzing differences among global approaches to gravitational field estimation. Such results can be used to justify model selection in applied tasks, particularly when determining optimal gravity corrections to heights that consider the specifics of terrain and mass anomalies at a local level. Application of this data enhances the accuracy of calculations in geodesy and other geosciences, ensuring a more reliable assessment of gravitational field parameters for various regions. Study object is the free-air gravity anomalies derived from global Earth gravity field models, specifically WGM2012, EGM2008, EIGEN-6C4, GECO, XGM2019e2159, and SGG UGM2. Scope of research is the accuracy of free-air gravity anomalies obtained using various global Earth gravity field models, as well as a comparison of these models to determine the optimal conditions for their application. The purpose of research is a comparative analysis of the accuracy of free-air gravity anomalies calculated using different global Earth gravity field models and the identification of optimal models for application in diverse geographical conditions and for specific geodetic tasks. Results of the research. A study was conducted on the accuracy of free-air gravity anomalies calculated using various global Earth gravity field models. Difference maps of gravity anomalies were created for each model, enabling a visual assessment of accuracy variations depending on the chosen model and regional conditions. Additionally, difference graphs of gravity anomalies between models were constructed, allowing for an analysis of deviation characteristics and the determination of optimal parameters for the application of these models in specific geodetic and geophysical tasks