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Regional Models

Canada (GSD95)

  Author: M. Veronneau     Created: 1995    Resp: M. Veronneau  
      Status: ON-DEMAND   

The Canadian Geoid Model GSD95 has been developed at the Geodetic Survey Division of Natural Resource Canada ( This gravimetric model extends from 41°N to 72°N and from 46°W to 142°W with a grid spacing of 5'. It is computed in three parts using a remove-restore technique. The first part is the spherical harmonic synthesis from the OSU91A geopotential model. The second part is the contribution of the local gravity measurements (reduced by the global field), which is computed by multi-band 2D-FFT with a standard Stokes kernel. In particular GSD95 is based on a million and a half surface gravity measurements on land and oceans coming from the Geodetic Survey Division, the U.S. National Geodetic Survey and the U.S. Defense Mapping Agency; gaps in the shipborne measurements are filled by satellite altimetry-derived gravity data. Finally, the third part is the primary indirect effect on the geoid, which is managed by Helmert's second condensation method. The geodetic reference system is NAD83. The geoid model is validated using GPS/levelling data, showing differences with a mean of -69.3 cm and a standard deviation of 41.3 cm, which goes down to 14.4 cm after filtering out systematic errors.

M. Veronneau (1996). The GSD95 geoid model for Canada. In: J. Segawa, H. Fujimoto, S. Okubo (eds.), Gravity, Geoid and Marine Geodesy, IAG Symposia Series, vol. 117, pp. 573-580, Springer Verlag.
M. Veronneau (1997). Evaluation of the NASA/NIMA Earth Geopotential Model (EGM96) over Canada. IGeS Bulletin, 6, pp. 47-69.

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