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A Preliminary Geoid Model for Africa

  • Conference paper
A Window on the Future of Geodesy

Part of the book series: International Association of Geodesy Symposia ((IAG SYMPOSIA,volume 128))

Abstract

Precise geoid models are essential for the conversion of GPS-derived heights to heights above sea level. Such a model is under development for the continent of Africa, as part of the African Geoid Project. A uniform 5′ grid of gravity anomalies has been derived from terrestrial gravity data and has been combined with a 5′ grid for the marine areas derived from satellite altimetry. The combined data set has been used with the EGM96 geopotential model in a remove-restore process to compute the geoid using two-dimensional convolution. The final result is a 5′ grid of geoidal heights covering the land mass of Africa. There are significant gaps in the available terrestrial gravity data — these gaps, coupled with the effects of errors in the DEM used for calculating the G1 term and in interpolating gravity anomalies, mean that the accuracy of this geoid model will be variable and generally less than desirable. Nevertheless, comparison with GPS/levelling data covering a small part of South Africa shows an RMS agreement of better than 10cm. Over a larger region (all of Egypt) the agreement is less satisfactory.

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Author information

Authors and Affiliations

  1. School of Architecture, Planning & Geomatics, University of Cape Town, South Africa

    C L Merry

  2. Escola Politécnica, Universidade de São Paulo, São Paulo, Brazil

    D Blitzkow

  3. Department of Civil Engineering, Minia University, Minia, Egypt

    H Abd-Elmotaal

  4. Department of Surveying, University of Khartoum, Khartoum, Sudan

    H H Fashir

  5. University College, Dar es Salaam, Tanzania

    S John

  6. Department of Surveying, University of Zimbabwe, Harare, Zimbabwe

    F Podmore

  7. School of Earth Science, University of Leeds, Leeds, UK

    J D Fairhead

Authors
  1. C L Merry
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  2. D Blitzkow
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  3. H Abd-Elmotaal
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  4. H H Fashir
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  5. S John
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  6. F Podmore
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  7. J D Fairhead
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Editor information

Editors and Affiliations

  1. D.I.I.A.R. — Surveying Section, Polytechnic of Milan, Piazza Leonardo da Vinci, 32, 20133, Milan, Italy

    Fernando Sansò

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© 2005 Springer-Verlag Berlin Heidelberg

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Merry, C.L. et al. (2005). A Preliminary Geoid Model for Africa. In: Sansò, F. (eds) A Window on the Future of Geodesy. International Association of Geodesy Symposia, vol 128. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-27432-4_64

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