Research Projects

The geoid, an equipotential surface of Earth's gravity field, is a fundamental reference for determining heights. Importance of geoid is advocated also by the National Geospatial Policy 2022, which targets developing a national geoid model by 2025 and a precise digital elevation model (DEM) by 2030. High-resolution DEMs, incorporates geoid model to provide orthometric heights and are critical for numerous applications. However, following are some challenges in geoid modelling in India 1. Inaccessible Terrain: Rugged mountains, deserts, dense forests, and coastal regions hinder the collection of gravity and levelling data. 2. Data Limitations: India lacks airborne gravity data for geodetic purposes, though such surveys are proposed by the Survey of India and the Indian Army. 3. Dependence on Foreign Software: Most geoid studies in India rely on external software like GRAVSOFT (by DTU, Denmark), except a few studies (e.g., Goyal, 2022). 4. Resource Constraints: Current models depend on coarse DEMs, which affect topographic corrections and hence, reliability of the developed geoid model. 5. Open Questions in Merging Heterogeneous Data: Combining terrestrial, airborne, shipborne, and satellite gravity data remains a computational challenge globally. Further, literature highlights the importance of Stokes’ integral for geoid modeling, which requires orthometric heights. However, challenges in collecting such data in rugged regions necessitate alternative theories like Hotine’s approach using gravity disturbances, though it is numerically intensive and unexplored in India. Hence, this project primarily aims to develop indigenous comprehensive computational packages based on in-house algorithms for handling heterogenous gravity data and therafter for geoid modelling using modified Stokes (1849) and Hotine (1969) theories, tailroed to Indian topography. Further, a set of statistical parameter and a strategy will be worked upon to provide a “statistical” definition of “consistently-cm-precise” and “consistently-cm-accurate” geoid, which is necessary yet missing from the literature. Since, presently India do not have heterogenous gravity data, the project will use Taiwan dataset (Hwang et al., 2020). During the project, Nepal would be pursued to work collaboratively with our software and their airborne gravity data. Further, if Indian data is collected by the end of 2nd year of project, our methods can be implemented on Indian dataset also. In summary, the project supports National Geospatial Policy 2022 and initiatives by the Survey of India and Indian Army to collect airborne gravity data and develop precise geoid model and DEMs. It also addresses open problems in geoid determination, especially integrating heterogeneous gravity data and Hotine’ theory, positioning India as a leader in Asia-Pacific geoid research. It also aligns with international efforts efforts under the International Association of Geodesy to achieve cm-level geoid models.