Testing global geopotential models through comparison of a local quasi-geoid model with GPS/leveling data |
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| Authors: | Pavel Novák Jan Kostelecký Jaroslav Klokočník |
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| Institution: | (1) Research Institute of Geodesy, Topography and Cartography, 250 66, Zdiby 98, Czech Republic;(2) University of West Bohemia, Department of Mathematics, Univerzitní 8, 306 14 Plzeň, Czech Republic;(3) Department of Advanced Geodesy, Czech Technical University, Thákurova 7, 166 29 Praha, Czech Republic;(4) Astronomical Institute of the Academy of Sciences of the Czech Republic, 251 65, Ondřejov, Czech Republic |
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| Abstract: | The satellite missions CHAllenging Minisatellite Payload (CHAMP) and Gravity Recovery And Climate Experiment (GRACE) provide
accurate data that are routinely inverted into spherical harmonic coefficients of the geopotential forming a global geopotential
model (GGM). Mean square errors of these coefficients, in some cases even entire covariance matrices, are included in the
GGM. Due to estimation procedures with a large redundancy and insufficiently propagated observation errors, they often do
not represent the actual accuracy of the harmonic coefficients, thus also gravity field parameters synthesized from the respective
GGM. Since in most cases standard methods validating the GGMs reached their limits, new procedures and independent data are
being currently sought. This article discusses an alternative validation procedure based on comparison of the GGMs with independent
data represented by a set of GPS/leveling stations. Due to a different spectral content of the height anomalies synthesized
from the GGMs and of those derived by combination of GPS-based ellipsoidal and leveled normal heights, the GGM-based low frequency
height anomaly is enhanced for a high frequency component computed from local ground gravity and elevation data. The methodology
is applied on a set of selected points of the European Vertical Reference Network and Czech trigonometric stations. In accordance
with similar tests based on entirely independent data of cross-over altimetry, obtained results seem to indicate low-frequency
deficiencies in the current GGMs, namely in those estimated from data of single-satellite missions. |
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| Keywords: | global geopotential models CHAMP GRACE quasi-geoid accuracy validation GPS/leveling cross-over altimetry |
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