Evaluation of GOCE/GRACE Global Geopotential Models over Greece with Collocated GPS/Levelling Observations and Local Gravity Data
International Association of Geodesy Symposia
The advent of the GOCE and GRACE missions during the last decade have brought new insights and promising results both in the static and time-variable representation of the Earth's gravity field. The focus of this work is directed to the evaluation of most available Global Geopotential Models (GGMs) from GOCE and GRACE, both satellite only as well as combined ones. The evaluation is carried out over an extensive network of collocated GPS/Levelling benchmarks (BMs) which covers the entire part of
... the entire part of continental Greece and with respect to the reductions the GGMs provide in existing gravity data in order to assess their performance in a scenario that a remove-compute-restore procedure would be followed for geoid determination. From the evaluation with GPS/Levelling BMs, it was concluded that the GOCE/GRACE GGMs provide an absolute accuracy at the 12-15 cm level, up to degree and order (d/o) 250, when considering the geoid omission error. This is comparable and in some cases better than the performance of EGM2008 in Greece. Moreover, the latest (Release 3) versions of the GGMs provide considerably better results compared to the earlier version by 1-5 cm. In terms of relative errors, GOCE/GRACE GGMs reach the 1 cm level for baselines between 50 and 60 km, while for longer ones, 80-90 km, their performance is analogous to the local geoid model and the ultra-high degree combined GGMs. Finally, GOCE/GRACE GGMs manage to provide the same, as EGM2008, level of reduction to the local gravity anomalies, with a std at the 26.7-27.8 mGal level, when evaluated up to d/o 250. accuracies in the representation of the Earth's gravity field within the spectral band up to d/o 160-220 ( 90-130 km) as far as GOCE and GOCE/GRACE models are concerned. Recent results from the evaluation of GOCE/GRACE based GGMs with terrestrial gravity data and deflections of the vertical (Hirt et al. 2011) show that GOCE offers improved results between d/o 160 and 185, since for larger degrees of expansion signal loss is experienced. The same results have been acquired by Šprlák et al. (2012) over Norway, evaluating the GGMs with terrestrial gravity data. The R1 versions of the GGMs have a std up to 4.5 mGal up to d/o 160-170 which increases to 180 for GO-DIR-R1.