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Regional Models

Baltic and Nordic Region (NKG2004)


  Authors: R. Forsberg, G. Strykowski, D. Solheim     Created: 2004    Resp: J. Agren  
      Status: PUBLIC    
Description:
The NKG2004 gravimetric quasigeoid model for the Nordic-Baltic countries has been computed by KMS (National Survey and Cadastre of Denmark) under the auspices of Nordic Geodetic Commission working group. It extends from 53°N to 73°N and from 1°E to 33°E with a grid spacing of 1.2'x2.4'. With respect to the previous NKG96 version, the NKG gravity database has been improved by incorporating Baltic Sea airborne surveys and new data from Sweden, Norway, Russia and Baltic countries. After neglecting gravity anomalies with error standard deviation larger than 8 mGal, a total number of 252,856 points of surface gravity data and 7,869 points of airborne gravity data was considered and gridded by Least-Squares Collocation. The NKG2015 quasigeoid was computed by the remove-restore approach by using a Wong and Gore type of modification, selected to high-pass filter the gravity anomalies above degree 30. The reference geopotential global model was the GRACE-based GGM02S spherical harmonic model up to degree 90, completed with EGM96 beyond degree 100 (linear blending). The SCANDEM 2004 elevation model was used to compute the residual terrain effect. The residual height anomalies were computed by Stoke's integration via Fast Fourier Transform (FFT). The resulting quasigeoid model was originally referred to WGS84, but then shifted by 35 cm to approximately match sea-level in the Nordic area. After that, the comparison with GNSS/levelling data shows differences with a standard deviation of 9.0 cm.

References:
R. Forsberg, G. Strykowski, D. Solheim (2004). NKG-2004 geoid of the Nordic and Baltic area. Proceedings on CD-ROM of the IAG International Symposium "Gravity, Geoid and Satellite Gravity Missions", 30 August - 3 September, 2004, Porto, Portugal.


Nordic and Baltic Countries