Continuous GPS Measurements At UK Tide Gauge Sites, 1997 - 2000

Norman Teferle

Abstract:	Long term changes in global mean sea level are corrupted by vertical land movements at tide gauge sites and hence, need to be monitored in order to separate the sea level variations from uplift or subsidence of the land surrounding the tide gauge. A network of permanent, continuous GPS (CGPS) stations has been established in the UK since 1997 to monitor vertical land movements at tide gauge sites. Accurate estimation of the rate of the vertical land movement and its uncertainty is necessary, but can be problematic when the CGPS time series are time- correlated, as has been shown by several authors in the past. This problem is investigated in this paper by comparing the derived uncertainties using two different estimation formulae. A spatial filtering technique that removes a common mode bias from the coordinate time series was applied. Two of the five CGPS stations that are sited at a tide gauge are relatively close to another CGPS station sited further inland on stable rock. This paper looks into the potential for using dual-CGPS stations. The GPS height time series of the five tide gauge GPS stations vary between 1.5 and 3.3 years in length and all indicate the presence of periodic variations. It is shown that vertical station velocities with a precision between 1.7 and 2.8 mm/yr can be achieved after 3.3 years depending on which formulae is used for computation. In nearly all height time series the common mode filter significantly reduced the spread and periodic variations. Remaining periodic signals can be assumed to be site specific. The initial results for the dual-CGPS stations suggest that this concept should provide better information for the decoupling of vertical land movements and changes in mean sea level.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	17 - 27
Cite this article:	Teferle, Norman, "Continuous GPS Measurements At UK Tide Gauge Sites, 1997 - 2000," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 17-27.
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