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Regional Models

Greenland (GGEOID16)

  Author: R. Forsberg     Created: 2016    Resp: R. Forsberg  
      Status: PUBLIC    

GGeoid16 is a gravimetric geoid model for Greenland, covering the area 58-85°N and 77-7°W with a grid resolution of 0.02° x 0.05° (approx. 2 km). It is based on a large set of land, marine, airborne and satellite gravity measurements, as well as digital terrain models for land and thickness of the inland ice. The geoid has been shifted by -15.6 cm from the global WGS84 computation system, to match the mean sea level at Nuuk. The GGeoid16 model is based on a previous preliminary model GGeoid14, with some changes in methods, new improved GOCE satellite data (Release 5), new aircraft-based gravity data from NASA OMG (Oceans Melting Greenland) project, as well as new gravity data from satellite altimetry (DTU13). The geoid determination is performed in the framework of a remove-restore procedure, using the DTU-Space GRAVSOFT package. The used global gravity model is EIGEN-6C4 up to degree and order 360, while the residual terrain correction is computed from a 500 m resolution land and ice thickness terrain model in Greenland and Iceland, and from a 1000 m resolution terrain model in Canada and Jan Mayen. A downward continuation and gridding of all gravity field data to the terrain surface is performed by block least squares collocation, and then residual quasi-geoid heights are derived by Stokes' integration through spherical Fast Fourier Transform. After restoring the terrain effect and the reference global gravity field, quasi geoid heights are finally converted to geoid heights. The resulting GGeoid16 model is used to define the GVR2016 vertical reference system in Greenland. The accuracy of GGEOID16 is highly dependent on the underlying gravity coverage and is estimated to be 5-10 cm in areas of good gravity coverage. In Iceland, the comparison between GGEIOD16 and recent GPS leveling measurements (311 points) shows an r.m.s. errors of 3.7 cm, and a bias of 9.9 cm (the bias mainly reflects the difference in mean sea level between Iceland and Nuuk).

R. Forsberg (2016). GGEOID16 - Opdateret geoide for Grønland - tilpasset havniveau i Nuuk. Report of National Space Institute at the Technical University of Denmark, Copenhagen, Denmark (in Danish).