Accuracy assessment of high and ultra high-resolution combined GGMs, and recent satellite-only GGMs - Case studies of Poland and Ethiopia

The launch of dedicated satellite gravity missions (CHAMP, GRACE, GOCE, and GRACE-FO), as well as the availability of gravity data from satellite altimetry and terrestrial/airborne gravity measurements have led to a growing number of Global Geopotential Models (GGMs) developed. Thus, the evaluation of GGMs is necessary to ensure their accuracy in recovering the Earth's gravity field on local, regional, and global scales. The main objective of this research is to assess the accuracy of recent GGMs over Poland in Central Europe and Ethiopia in East Africa. Combined GGMs of high (degree and order (d/o) 2190) and ultra high-resolution (d/o 5540) as well as five satellite-only GGMs were evaluated using gravity data from absolute gravity measurements and airborne gravity surveys over Poland and Ethiopia, respectively. Based on this evaluation, the estimated accuracy of the high-resolution combined GGM is at the level of 2 mGal. The estimated accuracy for the ultra-high-resolution combined GGM is similar to 2.5 times lower. The satellite-only GGMs investigated recover the gravity signal at an accuracy level of 10 mGal and 26 mGal, for the areas of Poland and Ethiopia, respectively. When compensating for the omitted gravity signal using a high-resolution combined GGM and the topography model, an accuracy of 2 mGal can be achieved.