From: Robert Duval / NRCan Subject: [IGSMAIL-1535] ALGO Antenna change 15-16 January Date: Tue, 4 Feb 1997 5:37:01 PST ****************************************************************************** IGS Electronic Mail Tue Feb 4 5:37:01 PST 1997 Message Number 1535 ****************************************************************************** Author: Robert Duval / NRCan Subject: ALGO Antenna change 15-16 January ADVISORY ======== Site name : ALGONQUIN 4 char ID : ALGO Monu inscription : 883160 Domes number : 40104M002 The reported antenna swap at ALGO was done on Jan 15/97 at about midnight UT (IGSMAIL# 1522). No significant phase centre changes were expected as the new (S/N #386) and the original (S/N #173) antennas are of the same type (DORNE MARGOLIN T), the only difference is that the new one has a new RF (low noise) filter. In order to verify that no significant antenna phase centre changes indeed occurred a nearby station (about 86m from ALGO) was occupied with Turbo Rogue & Dorne Margolin T antenna for two days, one day before (Jan 15) and one day after the change (Jan 16). Since the nearby station did not move (a force centred concrete pillar) and no significant changes occurred in the surrounding (the reflective/multipath) environment during the two days, it is expected that this station could verify (or detect) any phase centre (pc) changes at ALGO caused by the above antenna change. In the table below the change at ALGO (Jan 16-Jan15, or #386-#173) are listed for L3, L1 & L2 solutions. For this a regular IGS processing (i.e. stochastic tropo modeling & solutions) were used, though changes of up 3 mm (in the height only) were observed when tropo scaling was not solved or solved as a single parameter only. Difference at ALGO phase centre (Jan 16(S/N#386)-Jan 15(S/N#173) in mm L3 L1 L2 North -2.5 +-.5mm -.4 +- .2mm .9 +- .3 East -1.9 .5 -.3 .2 .9 .3 Up -2.1 2.8 -2.8 1.1 -3.2 1.5 Length -1.0 .5 -.2 .2 .3 .3 AS can be seen above the antenna pc changes could be considered insignificant at a mm level, in particular for the height, when taking into account the formal sigmas, and the fact that the same order of magnitude (height) variation was observed by changing the tropo scale (solution) modeling. -- Robert Duval Geodetic Survey Division, Natural Resources Canada (NRCan) 615 Booth Street Ottawa, Ontario, K1A 0E9 Tel: (613) 947-2786 Fax: (613) 995-3215 E-mail: duval@geod.nrcan.gc.ca ***************************************************************************** [Mailed From: Robert Duval ]