Assessment of geodetic velocities using GPS campaign measurements over long baseline lengths

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.

Accuracy of Deformation Rates from Campaign GPS Surveys Considering Extended Observation Session and Antenna Set-Up Errors

“…2019, 11, x FOR PEER REVIEW 7 of 12 baseline components. Secondly, the success rate of the vertical component showed about 85% improvement over the study of Duman and Sanli [23]. Extending the observation session from 8-10 h to 24 h significantly improved the vertical deformation rates estimated.…”

“…Velocity estimation was further degraded when antenna set up errors were introduced to GPS baseline components. Secondly, the success rate of the vertical component showed about 85% improvement over the study of Duman and Sanli [23].…”

“…The detailed results of the statistical hypothesis testing, which are not obvious in Figures 3 and 4 are given in Figure 5. It is seen from the figure that a tremendous amount of success was gained over the study of Akarsu, Sanli and Arslan [22] and Duman and Sanli [23]. First of all, the effect of antenna set-up errors were clearly seen on all three components (c.f.…”

“…On the other hand none of the vertical velocities derived from 8-12 h campaigns agreed with 24 h sessions. Duman and Sanli [23] applied a refinement procedure to Akarsu, Sanli and Arslan [22] to improve the success of the velocities derived from GPS campaigns. They eliminated the noisy time series obtained in the years 1992-1999 from the generation of campaign measurements, chose GPS days from quieter ionospheric conditions with a kappa index <4, used data from three consecutive days, reprocessed Jet Propulsion Laboratory (JPL) orbits and clocks were used in the analysis, and the east component was improved with the new single receiver ambiguity resolution algorithm of GIPSY/OASIS II.…”

“…Akarsu, Sanli and Arslan [22] and Duman and Sanli [23] used the full 15-year span of the available GPS time series. Furthermore, they used the International GNSS Service (IGS) data to sample the campaign measurements at once per month.…”