A computationally efficient approach for estimating high-rate satellite clock corrections in realtime |
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Authors: | Maorong Ge Junping Chen Jan Dou?a Gerd Gendt Jens Wickert |
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Institution: | (1) Helmholtz Centre Potsdam, German Research Centre for Geosciences (GFZ), Telegrafenberg, 14473 Potsdam, Germany;(2) Research Institute of Geodesy, Topography and Cartography, GO Pecny, 250 66 Ondrejov 244, Czech Republic |
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Abstract: | Realtime satellite clock corrections are usually estimated using undifferenced phase and range observations from a global
network. Because a large number of ambiguity parameters must be estimated, the computation is time-consuming. Consequently,
only a sparse global network of limited number of stations is processed by most IGS Realtime Analysis Centers with an update
rate of 5 s. In addition, it is very desirable to build the capability to simultaneously estimate clock corrections for multi-GNSS
constellations. Although the estimation can be sped up by epoch-differenced observations that eliminate ambiguities, the derived
clocks can contain a satellite-specific bias that diminishes the contribution of range observations. We introduce a computationally
efficient approach for realtime clock estimation. Both the epoch-differenced phase and undifferenced range observations are
used together to estimate the epoch-differenced satellite clocks and the initial clock bias for each satellite and receiver.
The biased clock corrections accumulated from the estimated epoch-differenced clocks are then aligned with the estimated clock
biases and provided as the final clock corrections to users. The algorithm is incorporated into the EPOS-RT software developed
at GFZ (GeoForschungsZentrum) and experimentally validated with the IGS global network. The comparison with the GFZ rapid
products shows that the accuracy of the clock estimation with the new approach is comparable with that of the undifferenced
approach, whereas the computation time is reduced to one-tenth. As a result, estimation of high-rate satellite clocks from
a large reference network and tracking satellites of multi-GNSS constellations becomes achievable. |
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