## 4 Conclusions  
From a global network of IGS stations, we carried out an experiment in which the ground deformation rate (i.e., velocity) due to tectonic motion estimated from campaign measurements was compared with the ground deformation rate obtained from continuous GPS data. Continuous GPS time series constructed for the IGS stations by NASA JPL were utilized in the analysis. Campaign GPS time series were generated by decimating the four-year continuous positioning solutions into monthly and four monthly samples. Learning lessons from the success of GPS campaigns performed with 8-12 h in the literature, we extended the duration of measurements to a full 24 h. In other words, synthetic campaigns from continuous data were generated using solutions from 24 h data. Previously it was found that determining tectonic motion from a traditional 8-12 h GPS campaigns was not comparable to the one produced from GPS campaigns using 24h data. With a careful refinement procedure, on the average only 50-70% of the velocities estimated for horizontal components were usable. Only 10% of the velocities produced from the vertical component of 8-12 h campaigns was comparable to the one produced from 24 h campaigns. These assessments were produced with 95% confidence level and considering a full 15-year time series. Here, we synthetically applied two different sampling from the continuous data; one measurement per month and one measurement per four months. Considering practical concerns we used four-year time series, which is a minimum data requirement for reliable deformation monitoring.  
In addition, in this phase of the work, we took into account antenna tripod set up errors on positioning. Note that the data sampled from continuous IGS stations neglected the antenna set up errors. Referring to the literature for the magnitude of the antenna error, GPS campaign measurements were synthetically biased. As expected, in general, the deformation rate obtained from GPS campaigns performed once per month agreed better with the deformation rate produced from continuous GPS. However, repeating GPS campaigns once every month would be cumbersome to many operators in the field. Here, the success of horizontal positioning accuracy by campaign measurements using observations once every four months had been improved by about 25-40% whilst the success of the vertical positioning had been improved by about 85% compared to previous studies. Extending the observation duration from 8 h to 24 h played the key role in gaining this.  
Note that the assessments made here were only for the determination of tectonic motion. The 1-sigma velocity estimation error of the campaign data was a factor of 5-10 coarser than those of the continuous data. The conclusions made here obviously would not apply to the monitoring of, say a fault creep requiring much more attention. For the assessment of GNSS stations in tectonically active regions, the reader should refer to site specific reports of the IGS and geological assessment of the region for better interpretations. Our overall conclusion is that the field operator is now very near to the 95% confidence level in monitoring of the tectonic motion especially for the north and up components if the observation session is extended to 24 h and campaigns are repeated every four months.  
D.U.S. developed the methodology. D.U.S. and Y.T. wrote the software. D.U.S. made the validations. Y.T. performed the formal analysis. D.U.S and Y.T. carried out the investigation. Y.T. wrote the original draft. D.U.S. did the review and editing. Y.T. made the visualization. D.U.S. supervised the study.  
This research received no external funding.  
We are grateful to NASA -- JPL for opening their GPS time series archives to worldwide research community. We are also grateful to The Generic Mapping Tools (GMT) for their open source codes. We thank to the four anonymous reviewers for their constructive comments.  
The authors declare no conflict of interest