Abstract
The aim of the current investigation is to determine an alternative geoid model for Africa using the shallow-layer method. The shallow-layer method, following the basic definition of the geoid, differs essentially from the traditional geoid determination techniques (Stokes and Molodensky) that it doesn’t need real gravity data. It comes from the definition of the geoid. Here, the shallow-layer method is used to determine a 5′ × 5′ geoid model for Africa covering the latitudes between −36°N and 39°N and longitudes from −20°E to 53°E The Earth Gravitational Model (EGM2008), the global topographic model (DTM2006.0), the global crustal model (CRUST1.0) and the Danish National Space Center data set (DNSC08) global models have been used to construct and define the shallow layer and its interior structure. A combination of prism and tesseroid modelling methods have been utilized to determine the gravitational potential produced by the shallow-layer masses. The validation and tests of the computed shallow-layer geoid have been done at two different levels. First, a comparison between the computed shallow-layer geoid and the recently developed AFRgeo2019 gravimetric geoid for Africa (based on real gravity data) has been carried out. Second, a comparison of the computed shallow-layer geoid with several geoid models computed using different global geopotential models has been performed. The results show that the computed shallow-layer geoid behaves similarly to those determined by the global geopotential models. Differences between the shallow-layer and the AFRgeo2019 gravimetric geoids are generally small (below 0.5 m) at most of the African continent
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Acknowledgements
The authors would like to express their sincere gratitude to professor Petr Holota, the Editor of the current paper, and the anonymous reviewers for their insightful comments and suggestions, which greatly helped to improve the quality of the manuscript. We would like to express our thanks to Prof. Gábor Papp for his valuable comments and critical suggestions towards enhancing the article. This study was supported by the National Natural Science Foundation of China (grants Nos 41631072, 42030105, 41721003, 41574007, and 41804012), the Discipline Innovative Engineering Plan of Modern Geodesy and Geodynamics (grant No. B17033), and the DAAD Thematic Network Project (grant No. 57173947).
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Ashry, M., Shen, WB. & Abd-Elmotaal, H.A. An alternative geoid model for Africa using the shallow-layer method. Stud Geophys Geod 65, 148–167 (2021). https://doi.org/10.1007/s11200-020-0301-0
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DOI: https://doi.org/10.1007/s11200-020-0301-0