Test Dataset 1 - Residual Stacking

Standard deviation of residuals - day 297-311 of 2000

Residuals have been stacked over a 15 day period from day 297 - 311 in 2000, using 1 degree steps in elevation. The standard deviation of the residual in each bin, in [mm], is plotted as function of zenith angle for each of the stations. The standard deviation of the residuals depends mainly on the receiver type and amount of multipath at the site. Plotted are

• Emperical standard deviation (computed from the residuals) - blue lines
• Emperical standard deviation (computed from the residuals) after correction for multipath - green lines
• Formal error of the residuals (computed from the co-variance matrix), - red lines

Apeldoorn (APEL) TRIMBLE 4700 TRM29659.00 UNAV	Delft (DELF) TRIMBLE 4700 TRM29659.00 UNAV	Eijsden (EIJS) TRIMBLE 4700 TRM29659.00 UNAV
Terschelling (TERS) TRIMBLE 4700 TRM29659.00 UNAV	Borkum (BORK) TRIMBLE 4000SSI TRM29659.00 SNOW	Zimmerwald (ZIMM) TRIMBLE 4000SSI TRM29659.00 NONE
Kootwijk AGRS (KOSA) TRIMBLE 4700 AOAD/M_B DUTD	Kootwijk IGS (KOSG) ROGUE SNR-12 RM AOAD/M_B DUTD	Onsala (ONSA) ASHTECH Z-XII3 AOAD/M_B OSOD
Westerbork AGRS (WSRA) TRIMBLE 4700 AOAD/M_T DUTD	Westerbork IGS (WSRT) AOA SNR-12 ACT AOAD/M_T DUTD	Potsdam (POTS) AOA SNR8000 ACT AOAD/M_T NONE
Wettzell (WTZR) AOA SNR8000 ACT AOAD/M_T NONE	Brussel (BRUS) ASHTECH UZ-12 ASH701945B_M NONE	Helgoland (HELG) ASHTECH Z-XII3 ASH700936D_M SNOW
Herstmonceux (HERS) ASHTECH Z-XII3 ASH700936E NONE	Euskirchen (EUSK) TRIMBLE 4000SSI TRM22020.00+GP

The following can be concluded from these results

• The emperical standard deviation (after correction for multipath) as function of elevation is the more or less the same for receivers of the same type and design, irrespective of the station
• The emperical standard deviation after correction for multipath is always smaller than the emperical standard deviation before correction, and the difference is the largest for sites with large multipath, see also the multipath maps
• From the difference between the standard deviation of the uncorrected and corrected residuals, we may conclude that there is significant multipath in Apeldoorn, Delft, Helgoland, and Euskirchen. This is confirmed by the mean residual maps, which show very characteristic patterns for these stations. For Euskirchen also elevation dependent delays in the antenna come into play, see the elevation dependent phase delay plots
• The residuals for Herstmonceux are larger than those of the other stations. This is confirmend by the maps of the emperical standard deviation of the residuals.
• Also the residuals for Terschelling are a little larger than the other stations, which could be caused by diffuse or non-repeatable multipath. The antenna in Terschelling is very close to a storage place for buoys, which are all equiped with radar relectors
• The standard deviations of the Turbo-Rogues, which smooth internally their phase data using a second degree polynomial over a period of not more than 10 second, is smaller than the standard deviation of the Trimbles.
• The standard deviation of the AOA SNR-12 ACT, which uses full tracking on all three signals (C1, P1 and P2) is better than the standard deviation of its predecessor the AOA SNR-12 RM, which uses cross-correlation of P1 and P2
• The emperical standard deviation (after correction for multipath) has a similar behaviour to the formal standard deviation of the residuals, but fine tuning of the elevation dependent weighting function in the analysis is advised. So far, we used 1/cos(z)² as elevation dependent weighting function for all receivers, assuming a standard deviation of 1 mm for the raw phase observables (i.e. 3 mm for the ionosphere free linear combination that we are using).
• The formal standard deviation of the residuals can be fitted reasonably well by a function of the type a + b*cos(z)²
• Kootwijk and Westerbork use two different receivers, connected to the same antenna by means of antenna slitters, which is an ideal situation for comparing receivers
• The main uncertainties are in the zenith, which is caused by lack of observations in the zenith direction