Evaluation of the NZGeoid05 using GPS levelling in rural and elevated locations, South Island, New Zealand

Abstract

To facilitate day to day surveying and mapping activities, Land Information New Zealand (LINZ) has developed a regional quasigeoid (NZGeoid05) by enhancing a global geopotential model with satellite, terrestrial and sea gravity data over the continental shelf of New Zealand (NZ). The overall national precision of NZGeoid05 was estimated by LINZ to be ±0.08 m (1σ). Six regions, distributed throughout the South Island of NZ, have been used to provide further independent verification of the precision of the NZGeoid05 by determining the geometric geoid-ellipsoid separation. In each region, several benchmarks with first-order normal-orthometric heights were selected and ellipsoidal heights measured independently using geodetic position techniques. A comparison has also been made with the global geopotential model, EGM2008. For NZGeoid05, four of the six regions tested have a RMS fit better than ±0.05 m, while for the EGM2008 this is only achieved in two regions. The estimated geoid slopes for both the NZGeoid05 and EGM2008 models agree with the geometric data to better than 1 cm/km in five of the six regions tested.