Abstract
The noise level of kinematic Global Positioning System (GPS) coordinates is much higher than static daily coordinates. Therefore, it needs to be improved to capture details of small sub-daily tectonic deformation. Multipath is one of the dominant error sources of kinematic GPS, which the sidereal filter can mitigate. With increasing interest in applying kinematic GPS to early postseismic deformation studies, we investigate the characteristics of multipath errors and the performance of the position-domain sidereal filter using 30-s kinematic coordinates with a length of nearly 5 days. Experiments using three very short baselines mostly free from atmospheric disturbances show that multipath signature in position-domain has better repeatability at longer periods, and sidereal filtering without low-pass filtering yields a lift of power spectral density (PSD) at periods shorter than 200 s. These results recommend an empirical practice of low-pass filtering to a sidereal filter. However, a moderate cut-off period maximizes the performance of the sidereal filter because of the smaller multipath signature at longer periods. The amplitude of post-sidereal-filtered fluctuation is less than 6 mm in standard deviation, which demonstrates the nearly lowest noise level of kinematic GPS used for postseismic and other tectonic deformation studies. Our sidereal filter is proven to mitigate several peaks of power spectral density at periods up to 100,000 s, but the period dependency of PSD is not fully alleviated by sidereal filtering, which needs future investigation.Graphical
Highlights
Global Navigation Satellite System (GNSS) observation is a powerful tool to study the surface deformation of the Earth
We investigate multipath errors and the performance of position-domain sidereal filtering to mitigate them from 30-s kinematic Global Positioning System (GPS) coordinates
Our experiments presented in this paper demonstrate the currently achievable lowest limit of the noise level of 30-s kinematic GPS coordinates used for the postseismic deformation as well as other tectonic deformation studies
Summary
Global Navigation Satellite System (GNSS) observation is a powerful tool to study the surface deformation of the Earth. While studies on tectonics-related phenomena often employ daily static solutions of GNSS, raw observations, namely, carrier-phase of microwave transmitted from satellites, are usually recorded at a much shorter interval, for instance, 30, 15, or 1 s (e.g., Bock et al 2000; Genrich and Bock 1992; Larson et al 2003), or sometimes even shorter (e.g., Galetzka et al 2015; Genrich and Bock 2006). Contrary to daily static solutions, kinematic analysis determines coordinates of antenna position at every observation epoch. Static coordinates miss postseismic deformation less than 24 h after the mainshock as well as fast deformation rate change soon after the mainshock (“early” postseismic deformation), but kinematic GNSS coordinates can capture such early postseismic deformation in detail. Improvement of kinematic coordinates, is crucial to gain more insights into postseismic deformation
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