IGS Analysis Center Workshop - IGS - NASA

Table 4.2 European Baseline Repeatability Sigmas (Jan 17-30, 1993)North(mm)East(mm)up(mm)Length(ppb)#KOSG-WETT (602km)IGSCOMCODEMRGFZ5.84.74.67.16.44.34.73.65.74.917.014.715.220.816.05.35.35.96.15.81414141414KOSG-MADR (1512km)lGSCOMCODEMRGFZ6.67.84.78.99.38.77.56.39.310.712.912.812.620.314,53.02.93.13.33.31414141414KOSG-TROM (2054km)IGSCOMCODEMRGFZ9.910.08.413.712.719.118.213.226.724.421.119.718.025.124.73.64.53.05.16.013131313135. SATELLITE CLOCK COMBINATION CONSIDERATIONSThe satellite clock offsets along with satellite orbits are required for all positioning applications.Furthermore satellite orbit and clock errors are usually highly correlated so it makes sense toinclude them in the orbit products as well. Most geodetic applications do not require very precisesatellite clocks, a precision of a few microseconds is sufficient to align orbits and observation data.Single station navigation and precise time transfers, on the other hand, need the utmost accuracyfor the satellite clocks as the satellite clock and orbit errors map directly into the results.Precise and optimal clock estimation from both pseudorange and phase data necessitates theundifferenced approach to the GPS data analysis. The usual double differencing data treatmentnearly eliminates, by design, both station and satellite clock errors. Thus, for double differencingan additional step utilizing pseudoranges is required. Such clock estimation is suboptimal as phasedata and other parameters (e.g. estimated tropospheric delays) are not available or used in thisprocess. Nevertheless such clock solutions would still be useful in particular when precisepseudorange observations are available and used along with precise orbits. Currently only one IGSCenter (EMR) estimates both satellite and station clocks and submits the satellite clock solutions53