Abstract
Abstract. GPS campaign measurements are frequently used in order to determine geophysical phenomena such as tectonic motion, fault zones, landslides, and volcanoes. When observation duration is shorter, the accuracy of coordinates are degraded and the accuracy of point velocities are affected. The accuracies of the geodetic site velocities from a global network of International GNSS Service (IGS) stations were previously investigated using only PPP. In this study, we extend which site velocities will also be assessed, including fundamental relative positioning. PPP-derived results will also be evaluated to see the effect of reprocessed JPL products, single-receiver ambiguity resolution, repeating survey campaigns minimum 3 days at the site, and eliminating noisier solutions prior to the year 2000. To create synthetic GPS campaigns, 18 globally distributed, continuously operating IGS stations were chosen. GPS data were processed comparatively using GAMIT/GLOBK v10.6 and GIPSY-OASIS II v6.3. The data of synthetic campaign GPS time series were processed using a regression model accounting for the linear and seasonal variation of the ground motion. Once the velocities derived from 24 h sessions were accepted as the truth, the results from sub-sessions were compared with the results of 24 h and hypothesis testing was applied for the significance of the differences. The major outcome of this study is that on global scales (i.e. over long distances) with short observation sessions, the fundamental relative positioning produces results similar to PPP. The reliability of the velocity estimation for GPS horizontal baseline components has now been improved to about 85 % of the average for observation durations of 12 h.
Highlights
GPS measurements were gathered from campaign surveys from the end of 1980s to mid-1990s
Tables generally consist of two columns, which includes the relative evaluation results from GAMIT/GLOBK v10.60 and the PPP results from GIPSY-OASIS II v6.3 software
Relative positioning results were produced from GAMIT/GLOBK
Summary
GPS measurements were gathered from campaign surveys from the end of 1980s to mid-1990s. Zhang et al (1997) studied stochastic properties of continuous GPS (19 month long) data from permanent stations. They extended their time series by 5 years and generated campaign GPS measurements. Velocities were estimated from those synthetically generated campaign measurements. Velocity estimation (i.e. standard) errors of campaign measurements were assessed, employing white noise and coloured noise models. The stochastic model derived from continuous measurements was recommended for finding the standard errors of deformation rates obtained from campaign measurements
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