Correcting for a time lag built into current Global Positioning System satellites can significantly enhance the accuracy of highly detailed GPS observations that are increasingly used to study Earth systems. Choi et al. report that existing satellite techniques often slightly misjudge the location of ground changes, such as seismic activity, ice sheet flow, and volcanic deformation, because researchers used the wrong time delay in the GPS satellites.
The authors show that the orbit period varies for each satellite and often differs considerably from what scientists have assumed since the GPS constellation was begun in the late 1970s.
The researchers examined, for example, a GPS dataset from the well-observed 2003 San Simeon earthquake and found that high-precision (1 Hertz) GPS data needed to be corrected by nine seconds. They suggest that the improved processing technique would greatly reduce current error rates and make it possible to more accurately measure dynamic ground motion across the globe.
Title: Modified sidereal filtering: Implications for high-rate GPS positioning
Authors: Kyuhong Choi, Andria Bilich, Kristine M. Larson, Penina Axelrad, University of Colorado, Boulder, Colorado, USA.
Source: Geophysical Research Letters (GL) paper 10.1029/2004GL021621, 2004
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