 Questions about the day boundary clock discontinuity graphs...as displayed on the "site pages" reachable from the station list or clickable map.
The absolute accuracy of GPS-based clock estimates (modulo calibration) are determined entirely from the pseudorange data, averaged over the analysis arc, which is typically 24 h. When analysing 1 d arcs of global data sampled at 5-minute intervals, such estimates typically have formal errors of about 120 ps assuming a 1 m uncertainty of the pseudorange data. A more realistic assessment of the true timing uncertainty may be obtained by observing the boundaires between successive arcs of independently reduced data for those receivers equipped with high performance clocks. For sites externally driven by Hydrogen Masers, the day boundary plots show the repeatability of the geodetic time transfer technique between each successive days of processing. The Rapid and Final IGS Combined Clock estimates for each site shown have been referenced to the IGS Rapid Timescale (IGRT) and the IGS Final Timescale (IGST) respectively and the discontinuity between successive arcs has been calculated and plotted, one point for each day boundary. For a more detailed description of this station performance measure, see the article, "Geodetic techniques for time and frequency comparisons using GPS phase and code measurements," Metrologia,42 (2005) 215--232. |
|
| HOME || ABOUT IGS || ORGANIZATION || FAQs || FTP ARCHIVES || WEBSITE INDEX |
This page last updated: 13 May 2010 |