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Regional Models

Vietnam


  Authors: D.T. Vu, S. Bruinsma, S. Bonvalot     Created: 2019    Resp: D.T. Vu  
      Status: PUBLIC    
Description:
This is a gravimetric quasi-geoid model for Vietnam and its surrounding areas. The reference ellipsoid is WGS84. A set of 29,121 land gravity measurements was used in combination with fill-in data where no gravity data existed. A combination of EGM-DIR-R5 (up to d/o 260) and EGM2008 (from d/o 261 to 2159) plus residual terrain correction was used to provide the fill-in information over land, while the DTU15 gravity field derived from altimetry satellites was used for marine areas. Two quasi-geoid determination techniques were implemented in the framework of the remove-restore procedure, namely the Stokes integral using the Fast Fourier Transform approach and deterministic kernel modification proposed by Wong–Gore, and the Least-Squares Collocation approach. The long wavelength information came from the satellite-only EGM-DIR-R5 model up to d/o 260 and EGM2008 from d/o 261 to 719. Residual terrain correction was based on the SRTM3arc_v4.1 digital terrain model over land, and from the (3" resampled) SRTM15arc_plus digital bathymetry model over sea. The accuracy of the two resulting quasi-geoid models, called GEOID_FFT and GEOID_LSC, was evaluated by comparing them with height anomalies derived from 812 GNSS/levelling points. These differences have a standard deviation of 9.7 cm and a mean bias of 50 cm for both models.

Reference:
D.T. Vu, S. Bruinsma, S. Bonvalot (2019). A high-resolution gravimetric quasigeoid model for Vietnam. Earth, Planets and Space 71, 65. DOI: 10.1186/s40623-019-1045-3


Vietnam