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| Titel |
Estimating the Geocenter from GNSS Observations |
| VerfasserIn |
Rolf Dach, Michael Meindl, Gerhard Beutler, Stefan Schaer, Simon Lutz, Adrian Jäggi |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092083
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| Publikation (Nr.) |
 EGU/EGU2014-6408.pdf |
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| Zusammenfassung |
| The satellites of the Global Navigation Satellite Systems (GNSS) are orbiting the Earth
according to the laws of celestial mechanics. As a consequence, the satellites are sensitive to
the coordinates of the center of mass of the Earth. The coordinates of the (ground) tracking
stations are referring to the center of figure as the conventional origin of the reference frame.
The difference between the center of mass and center of figure is the instantaneous
geocenter.
Following this definition the global GNSS solutions are sensitive to the geocenter.
Several studies demonstrated strong correlations of the GNSS-derived geocenter
coordinates with parameters intended to absorb radiation pressure effects acting on the
GNSS satellites, and with GNSS satellite clock parameters. One should thus pose the
question to what extent these satellite-related parameters absorb (or hide) the geocenter
information.
A clean simulation study has been performed to answer this question. The simulation
environment allows it in particular to introduce user-defined shifts of the geocenter
(systematic inconsistencies between the satellite’s and station’s reference frames). These
geocenter shifts may be recovered by the mentioned parameters – provided they were set up
in the analysis. If the geocenter coordinates are not estimated, one may find out
which other parameters absorb the user-defined shifts of the geocenter and to what
extent.
Furthermore, the simulation environment also allows it to extract the correlation matrix
from the a posteriori covariance matrix to study the correlations between different
parameter types of the GNSS analysis system. Our results show high degrees of
correlations between geocenter coordinates, orbit-related parameters, and satellite
clock parameters. These correlations are of the same order of magnitude as the
correlations between station heights, troposphere, and receiver clock parameters in each
regional or global GNSS network analysis. If such correlations are accepted in a
GNSS analysis when estimating station coordinates, geocenter coordinates must be
considered as mathematically estimable in a global GNSS analysis. The geophysical
interpretation may of course become difficult, e.g., if insufficient orbit models are
used. |
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