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Geoid of Nepal from Airborne Gravity Survey

  • Rene Forsberg
  • Arne Vestergaard Olesen
  • Indridi Einarsson
  • Niraj Manandhar
  • Kalyan Shreshta
Conference paper
Part of the International Association of Geodesy Symposia book series (IAG SYMPOSIA, volume 139)

Abstract

An airborne gravity survey of Nepal was carried out December 2010 in a cooperation between DTU-Space, Nepal Survey Department, and NGA, USA. The entire country was flown with survey lines spaced 6 nm with a Beech King Air aircraft, with a varying flight altitude from 4 to 10 km. The survey operations were a major challenge due to excessive jet streams at altitude as well as occasional excessive mountain waves. Despite the large 400 mGal + range of gravity anomaly changes from the Indian plains to the Tibetan Plateau, results appear accurate to few mGal, with proper evaluation from cross-overs complicated by the high varying flight altitudes. Using a downward continuation scheme based on blocked least-squares collocation, a new geoid of Nepal was computed by Fourier methods. The new geoid shows large changes to EGM08, illustrating the impact of the new data. The new geoid is compared to limited GPS-levelling data as well as recent GPS-heights of Mt. Everest, and the new data also provide an independent validation of GOCE gravity field models at the local ∼100 km resolution scale.

Keywords

Airborne gravimetry Geoid Nepal 

Notes

Acknowledgements

We thank the COWI pilots for professional flight operations under the challenging conditions, and the Nepalese Army for allowing access to Kathmandu military airport facilities. We also thank F. Palmeri and G. Poretti, OGS and CNR, Italy, for providing additional surface gravity data in Nepal to aid in the geoid determination. Economic support for the Nepal airborne gravity project was proved by NGA and DTU.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Rene Forsberg
    • 1
  • Arne Vestergaard Olesen
    • 1
  • Indridi Einarsson
    • 1
  • Niraj Manandhar
    • 2
  • Kalyan Shreshta
    • 2
  1. 1.National Space Institute, Technical University of DenmarkCopenhagen OeDenmark
  2. 2.Survey DepartmentMinistry of Land Reform and ManagementKathmanduNepal

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