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A continuous GPS coordinate time series analysis strategy for high-accuracy vertical land movements Teferle, Felix Norman ; ; et al in Physics and chemistry of the earth (2008), 33(3-4), 205-216 A CGPS coordinate time series analysis strategy was evaluated to determine highly accurate vertical station velocity estimates with realistic uncertainties. This strategy uses a combination of techniques ... [more ▼] A CGPS coordinate time series analysis strategy was evaluated to determine highly accurate vertical station velocity estimates with realistic uncertainties. This strategy uses a combination of techniques to 1) obtain the most accurate parameter estimates of the station motion model, 2) infer the stochastic properties of the time series in order to compute more realistic error bounds for all parameter estimates, and 3) improve the understanding of apparent common systematic variations in the CGPS coordinate time series, which are believed to be of geophysical and/or technical origin. The strategy provided a pre-processing of the coordinate time series in which outliers and discontinuities were identified. Subsequent parameterization included a mean value, a constant rate, periodic terms with annual and semi-annual frequencies, and offset magnitudes for identified discontinuities. All parameters plus the magnitudes of different stochastic noise were determined using Maximum Likelihood Estimation (MLE). Empirical Orthogonal Function (EOF) analysis was used to study both the temporal and spatial variability of the common modes determined by this technique. After outlining the CGPS coordinate time series analysis strategy this paper shows initial results for coordinate time series for a four year (2000-2003) period from a selection of CGPS stations in Europe that are part of the European Sea Level Service (ESEAS) CGPS network. [less ▲] Detailed reference viewed: 57 (2 UL)A detailed analysis of tropospheric effects on geodetic observations at TMGO ; van Dam, Tonie ; et al in Physics and chemistry of the earth (1998), 23(1), 103-106 Improvements in geodetic tools are making previously subtle effects significant. Two examples affecting GPS observations are atmospheric loading of the Earth's crust and the tropospheric delays ... [more ▼] Improvements in geodetic tools are making previously subtle effects significant. Two examples affecting GPS observations are atmospheric loading of the Earth's crust and the tropospheric delays, specifically the wet component. Each measurement, tropospheric delays and site coordinates, requires unambiguous determination of the other to achieve the highest accuracy. Table Mountain Geophysical Observatory (TMGO) is a unique site where a long history of observations from two complementary techniques, GPS and superconducting gravimetry, have been accrued. In particular, the superconducting gravity measurements provide a unique baseline for evaluating GPS vertical estimates over a variety of time frames. Positional estimates for TMGO using these techniques will be compared. Tropospheric effects will be identified and discussed. The ability for GPS to make subdaily, daily, and long term vertical estimates will be evaluated. [less ▲] Detailed reference viewed: 69 (0 UL)Modeling environmental loading effects, Invited, Proceedings EGGS, Ed. H.-P. Plag and S. Zerbini van Dam, Tonie ; in Physics and chemistry of the earth (1998), 23 Temporal variations in the geographic distribution of atmospheric, hydrologic and oceanic mass load and deform the surface of the Earth. In many instances, the deformation is large enough to be detected ... [more ▼] Temporal variations in the geographic distribution of atmospheric, hydrologic and oceanic mass load and deform the surface of the Earth. In many instances, the deformation is large enough to be detected with space based geodetic techniques as well as with terrestrial gravity observations. For example, atmospheric loading induced crustal deformations on the order of 20 mm are possible at high latitudes with accompanying changes in gravity of 6 μGals. Non-tidal ocean loading effects can typically cause 5 mm (2 mm root-mean-square, RMS) in vertical positioning at coastal geodetic sites with displacements of up to 10 mm possible. Deformation associated gravity changes are usually on the order of 2-3 μGals, however peak-to-peak changes of 5 μGals are also predicted. The effects of regional ground water variations on geodetic measurements are less well known. Model results indicate that annual changes in gravity and vertical positioning can be as large as 2 μGals and 5 mm for sites where there is significant annual snowfall. We present a review of work done to date to address these issues. [less ▲] Detailed reference viewed: 54 (1 UL) |
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