Compilation of the regional quasigeoid model for New Zealand using the discretised integral-equation approach

We evaluate the new regional quasigeoid model (OTG12) for New Zealand using the method which utilises the discretised integral-equation approach for computing the near-zone contribution. The far-zone contribution is computed by modified spherical harmonics of the geopotential. Adopting the remove-compute-restore computation scheme, the near- and far-zone contributions are computed for the residual height anomalies, while the reference height anomalies are evaluated using a global gravitational model. For the numerical realisation, the GOCO-02S coefficients complete to degree 55 of spherical harmonics are used to generate the reference gravity field. The 1 x 1 arc-min grid data of terrestrial gravity anomalies are used to compute the near-zone contribution. The far-zone contribution is evaluated using the EGM2008 coefficients at the frequency bound between degrees 56 and 2160 of spherical harmonics. The newly-adjusted levelling data are used to validate the available regional geoid/quasigeoid models. The accuracy assessment of gravimetric solutions at GNSS-levelling testing network reveals that the accuracy of OTG12 is compatible with the existing regional geoid/quasigeoid models; the standard deviation (STD) of residuals between the geometric and gravimetric height anomalies is 13 cm (after applying the 3-parameter correction model).