HR: 1330h
AN: G52B-0042    [PDF]
TI: The Effect of SCIGN Domes on the Vertical Antenna Phase Centre Position in Routine Processing of GPS Data
AU: Schmidt, M
EM: schmidt@pgc.nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre, 9860 West Saanich Rd., Sidney, BC V8L 4B2 Canada
AU: * Dragert, H
EM: dragert@pgc.nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre, 9860 West Saanich Rd., Sidney, BC V8L 4B2 Canada
AU: Lu, Y
EM: lu@pgc.nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre, 9860 West Saanich Rd., Sidney, BC V8L 4B2 Canada
AU: Schofield, B
EM: schofield@pgc.nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre, 9860 West Saanich Rd., Sidney, BC V8L 4B2 Canada
AB: The question of phase centre shifts for GPS antennas introduced by the addition of domes is receiving more attention as the number of continuous GPS sites multiply and the precision of solutions continue to improve. Our earliest experiences with clear acrylic domes used in the Western Canada Deformation Array (WCDA) had shown that changes in the vertical position of the phase centre exceeding 1.5 cm could be caused by the introduction of a dome. More recently, our deployments of SCIGN domes at WCDA sites showed no discernable shifts in the horizontal components but apparent shifts of over 2 cm in the estimates of height. Such large shifts have also been observed in practice by others but have remained puzzling since calibration tests carried out by SCIGN and by NGS indicate maximum vertical shifts of only a few millimetres. Tests with the SCIGN short dome carried out at our GPS site at the Pacific Geoscience Centre (PGC5) demonstrate clearly that domes can introduce an elevation-dependent (1/cosZ) delay and consequently, the nominal mounting of SCIGN domes biases the tropospheric zenith delay resulting in an apparent shift in the L3 estimate of station height. Since estimates of the tropospheric delay are strongly dependent on the elevation cut-off used in the analysis as well as local site horizons, it is not possible to provide an "absolute" calibration correction for this effect. However, mounting the SCIGN dome so that its centre of curvature coincides with the mean position of the L1/L2 phase centres of the Dorne Margolin element significantly reduces this bias and effectively eliminates the large spurious change in height. This "dome effect" can be explained in terms of "lensing" of incident plane waves inside the dome.
DE: 0609 Antennas
DE: 0689 Wave propagation (4275)
DE: 1243 Space geodetic surveys
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2003 Fall Meeting