The New Zealand gravimetric quasigeoid model 2017 that incorporates nationwide airborne gravimetry

Abstract

A one arc-minute resolution gravimetric quasigeoid model has been computed for New Zealand, covering the region 25°S to 60°S and 160°E to 170°W. It was calculated by Wong-Gore modified Stokes integration using the removecompute-restore technique with the EIGEN-6C4 global gravity model as the reference field. The gridded gravity data used for the computation consisted of 40,677 land gravity observations, satellite-altimetry-derived marine gravity anomalies, historical shipborne marine gravity observations and, importantly, approximately one million new airborne gravity observations. The airborne data were collected with the specific intention of reinforcing the shortcomings of the existing data in areas of rough topography inaccessible to land gravimetry and in coastal areas where shipborne gravimetry cannot be collected and altimeter-derived gravity anomalies are generally poor. The new quasigeoid has a nominal precision of ±48 mm on comparison to GPS-levelling data, which is approximately 14 mm less than its predecessor NZGeoid09.

Evaluating temporal stability of the New Zealand quasigeoid following the 2016 Kaikōura earthquake using satellite radar remote sensing

“…5a). We used the same integration parameters as used for NZGeoid2017 (McCubbine et al 2018b), that is a degree-160 Wong & Gore (1969) modified Stokes's integral over a spherical cap radius of 2.5 • . The maximum quasigeoid change is +5 mm and is centred at the point where the most land uplift occurred.…”

“…Modified Stokes kernels in conjunction with the remove-compute restore procedure for regional quasigeoid solutions can deliver better agreements with independent GPS-levelling data, for example from empirical tests in New Zealand (McCubbine et al 2018b) and elsewhere [too many to cite here]. This is due to the reduction of long-wavelength terrestrial gravity data errors that are not present in a vertical deformation model.…”

“…To assess the possible change in the quasigeoid with respect to differences between the two theoretical approaches, we experiment with (i) forward modelling of the gravity change from the changed topography as measured by SAR, then Stokes-integrate this using the same parameter choices as used for NZGeoid2017 (McCubbine et al 2018b) and (ii) determining the change in gravitational potential purely from forward gravity modelling, then converting this to quasigeoid changes via Bruns's formula. In the latter case, both forward modelling approaches (gravitational and potential) use the right-rectangular prism method of Nagy et al (2000).…”

Gravimetric Geoid Modelling Over Peninsular Malaysia Using Two Different Gridding Approaches for Combining Free Air Anomaly

“…The optimal combination of these data with terrestrial gravity observations (which have different levels of accuracy) is a crucial consideration prior to modelling the quasigeoid. We analyse the effect of two different strategies, (i) following McCubbine et al (2018) and (ii) Kiamehr (2007), on the regional geoid models determined via the KTH method with respect to GNSS-levelling derived geoid undulations. Only terrestrial and marine gravity data have been used in the computations we present.…”

Improvement of Downward Continuation Values of Airborne Gravity Data in Taiwan

“…There are many regions in the world where airborne gravity surveys have been carried out [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The Taiwan airborne gravimetry project was conducted over many hills and high mountains.…”