[G02-P] Poster

[G02-P-01] Comparison of spherical and spheroidal harmonics for ultra-high-resolution global gravity modelling

^○Sten Claessens (Curtin University)

Spherical harmonic coefficients have for many decades routinely been used to represent the Earth's external gravitational and topographic potential fields. While it has long been recognised that a spheroidal (oblate ellipsoidal) harmonic series may be better suited to the description of the Earth's gravitational field given the significant flattening of the Earth, spherical harmonics continue to be used, mostly for practical reasons. For example, all global gravity and topographic potential models listed by the International Centre for Global Earth Models (ICGEM) are expressed as a spherical harmonic series. However, with the ever-increasing resolution of global models, the question is whether spherical harmonics continue to be the best basis functions to use. This presentation provides a comparison between spherical and spheroidal harmonic expansions to ultra-high degree and order (d/o). The maximum d/o of ICGEM models is 2190, but models to higher d/o (e.g. 10,800) have been and are being developed by several research groups. Some theoretical, numerical and practical challenges in the creation and use of these ultra-high degree models, both in terms of spherical and spheroidal harmonics, are outlined.