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Regional Models

New Zealand (NZGEOID05)


  Authors: : M.J. Amos, W.E. Featherstone     Created: 2005    Resp: M.J. Amos  
      Status: PUBLIC    
Description:
The New Zealand Quasigeoid 2005 (NZGeoid05) was the official geoid for New Zealand until it was replaced by the NZGeoid09 in September 2009. The NZGeoid05 model is distributed by Land Information New Zeland (LINZ), it is produced on a two arc-minute grid (approximately 3.7 kilometres) over the New Zealand continental shelf (160° E to 170° W, 25° S to 60° S) and it is referred to the GRS80 ellipsoid. It was calculated by enhancing the EGM96 global model using a combination of land, sea and satellite based gravity observations, while GPS-levelling observations were not used. In particular, firstly the global gravity model up to degree and order 360 was removed from the gridded gravity anomalies in the computation area and then the residual anomalies were subjected to a 1D FFT Stokes integration with kernel modifications, i.e. the kernel was set to zero outside the integration cap radius before being transformed into the frequency domain. The quasi-geoid is finally obtained by adding back the global model contribution. The method is iterated to account for the offsets among the 13 different local vertical datums in New Zealand, thus providing corrections to the input gravity anomalies. The NZGeoid05 model has an expected accuracy of 8 cm based on comparisons with GPS-levelling observations throughout New Zealand.

References:
M.J. Amos (2007). Quasigeoid modelling in New Zealand to unify multiple local vertical datums. PhD Thesis, Department of Spatial Sciences, Curtin University of Technology, Perth, Australia.
M.J. Amos, W.E. Featherstone (2009). Unification of New Zealand's local vertical datums: iterative gravimetric quasi-geoid computations, Journal of Geodesy, 83(1), pp. 57-68.

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