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CoverNewton's Bulletin

Issue n. 5, June 2015 - Assessment of GOCE Geopotential Models    [pp. 127-148]

Assessments of Recent GRACE and GOCE Release 5 Global Geopotential Models in Canada

J. Huang, M. Véronneau

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The objective of this study is to assess the recent GRACE and GOCE release 5 (R5) global geopotential models (GGM) in Canada. For the evaluation of the GGM against GPS-Levelling data and deflections of the vertical, the satellite models need to be combined with terrestrial gravity data to determine highresolution geoid models. This process allows a significant reduction of the omission error in the satellite gravity models. The geoid computation is founded on the remove-compute-restore Stokes-Helmert scheme, in which the Stokes kernel function modification is used to constrain the regional geoid models to the spectral bands of the satellite model to be assessed. The resulting geoid models are directly comparable to the GPS-Levelling data, and these same geoid models can be used to derive deflections of the vertical which are compared to astronomic deflections. The data analysis indicates that the GOCE R5 models provide better precision than the GOCE release 4 (R4) models beyond degree and order 180. The accuracy of the GOCE R5 models is estimated to be better than 4-5 cm up to spherical harmonic degree ∼200. The astronomic deflections appear not accurate enough to measure improvements in the GOCE R5 models with respect to the GOCE R4 models. For the validation of GGM against terrestrial gravity data over land, EIGEN-6C4, which includes a GOCE R5 model, is assessed in contrast to EGM2008. Our analysis infers that the GOCE contribution in EIGEN-6C4 is more accurate than the corresponding wavelength components in EGM2008, which includes the Canadian terrestrial gravity data.