Test Dataset 1 - Residual Stacking

Mean residual versus elevation - Comparison between different periods

Residuals have been stacked over three different periods in 2000. After the first period, there have been some changes in antenna with respect to the second and third, or main, period. This allows us to investigate the effect of antenna changes on the one hand, and sensitivity and repeatability of the residual stacking on the other hand. The three main periods are

Day 110-117 2000 (8 days)
The Dutch stations Delft, Eijsden and Terschelling used different antenna and receivers compared to the other two periods.
Day 200-207 2000 (8 days)
Actually, the antenna and receiver in Delft has been changed during the middle (day 205) of the 2nd period. Therefore, results for Delft are analysed for 5 days directly before the change (day 199-204) and 5 days directly after the change (day 206-211).
Day 297-311 2000 (15 days). This is the main period.

Three different antenna designs are analysed:

TRM29659.00 UNAV Trimble Choke-Ring antenna with Dorne-Margolin element, with spherical radome (UNAVCO design).
AOAD/M_T DUTD AOA Dorne-Margolin Choke-Ring antenna with conical radome (DUT design).
AOAD/M_B DUTD AOA Dorne-Margolin Choke-Ring antenna with conical radome (DUT design), similar to AOAD/M_T DUTD, but a slightly different design.

All these antenna are Choke-Ring antenna of similar, albeit not identical design, using different type of radomes.

The mean residual in 1 degree steps of elevation are show below in [mm] for the different periods.

Period 1 day 110-117 2000 (8 days)	Period 2 day 200-207 2000 (8 days)	Period 3 (main period) day 297-311 2000 (15 days)
Delft (DELF) AOA SNR-12 RM AOAD/M_T DUTD	Delft (DELF) AOA SNR-12 RM AOAD/M_T DUTD	In Delft the receiver and antenna where changed during the middle of the 2nd period. In the middle column (to the left) is plotted day 199-204. In the middle column on the next row is plotted day 206-211.
	Delft (DELF) TRIMBLE 4700 TRM29659.00 UNAV	Delft (DELF) TRIMBLE 4700 TRM29659.00 UNAV
Eijsden (EIJS) AOA SNR-12 RM AOAD/M_T DUTD	Eijsden (EIJS) TRIMBLE 4700 TRM29659.00 UNAV	Eijsden (EIJS) TRIMBLE 4700 TRM29659.00 UNAV
Terschelling (TERS) AOA SNR-12 RM AOAD/M_T DUTD	Terschelling (TERS) TRIMBLE 4700 TRM29659.00 UNAV	Terschelling (TERS) TRIMBLE 4700 TRM29659.00 UNAV
Westerbork IGS (WSRT) AOA SNR-12 ACT AOAD/M_T DUTD	Westerbork IGS (WSRT) AOA SNR-12 ACT AOAD/M_T DUTD	Westerbork IGS (WSRT) AOA SNR-12 ACT AOAD/M_T DUTD
Westerbork IGS and AGRS use the same antenna, but are different receivers.	Westerbork AGRS (WSRA) TRIMBLE 4700 AOAD/M_T DUTD	Westerbork AGRS (WSRA) TRIMBLE 4700 AOAD/M_T DUTD
Kootwijk IGS (KOSG) ROGUE SNR-12 RM AOAD/M_B DUTD	Kootwijk IGS (KOSG) ROGUE SNR-12 RM AOAD/M_B DUTD	Kootwijk IGS (KOSG) ROGUE SNR-12 RM AOAD/M_B DUTD
Kootwijk IGS and AGRS use the same antenna, but are different receivers.	Kootwijk AGRS (KOSA) TRIMBLE 4700 AOAD/M_B DUTD	Kootwijk AGRS (KOSA) TRIMBLE 4700 AOAD/M_B DUTD

Click on the pictures to enlarge.

The following can be concluded from these results

The low period variation of the mean residuals as function of elevation is the same for antenna's of the same type and design, irrespective of the period
The low period variation is caused by elevation dependent delays as a result of the antenna design and radome that is used
The high periodic variations/modulation is caused by azimuth/elevation dependent near-field effects (multipath), which alias in the elevation dependent maps, see also the multipath maps
Kootwijk and Westerbork use two different receivers, connected to the same antenna by means of antenna slitters. The results are very identical, indication that the elevation dependent and azimuth dependent effect originate in the antenna, radome and/or near field environment (multipath). Differences in receiver performance can be observed in the plots of empiral and formal standard deviation
Results are very similar from one period to another, as long as the same antenna is used
The main differences are in the zenith, which is caused by lack of observations in the zenith direction

The tables for the elevation dependent phase center corrections in the GPS processing software should be corrected. Presently, we have used the default table as proposed by IGS, but these do not take into account the effect of radomes.

It remains to be seen, in case of improved elevation dependent corrections, whether multipath is or is not affected by antenna changes. The first impression from the multipath maps is that most important structures remain also after an antenna change, taking into account the changed elevation dependency