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Improvements in the analyses of Global Positioning System (GPS) obser- vations yield resolvable mm to sub-mm dierences in coordinate estimates, thus provid- ing sucient resolution to distinguish subtle dierences in analysis methodologies. Here we investigate the eects on site coordinates of using dierent approaches to modelling atmospheric loading deformation (ATML) and handling of tropospheric delays. The rig- orous approach of using the time-varying VMF1 mapping function yields solutions with lower noise at a range of frequencies compared with solutions generated using empiri- cal mapping functions. This is particularly evident when ATML is accounted for. Some improvement also arises from using improved a priori zenith hydrostatic delays (ZHD), with the combined eect being site specic. Importantly, inadequacies in both mapping functions and a priori ZHDs not only introduce time correlated noise but signicant pe- riodic terms at solar annual and semi-annual periods. We nd no signicant dierence between solutions where non-tidal ATML is applied at the observation level rather than as a daily-averaged value but failing to model diurnal and semi-diurnal tidal ATML at the observation level can introduce anomalous propagated signals with periods that closely match the GPS draconitic annual (351.4 d) and semi-annual period (175.7 d). Ex- acerbated by not xing ambiguities, these signals are evident in both stacked and sin- gle site power spectra, with each tide contributing roughly equally to the dominant semi- annual peak. The amplitude of the propagated signal reaches a maximum of 0.8 mm with a clear latitudinal dependence that is not correlated directly with locations of maximum tidal amplitude. This is the first evidence of aliased signals being produced from tidal ATML deformations.

Item Type:	Refereed Article
Keywords:	Global Positioning System (GPS); Atmospheric effects; Atmospheric loading deformation
Research Division:	Engineering
Research Group:	Geomatic Engineering
Research Field:	Geodesy
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Earth Sciences
Author:	Watson, CS (Dr Christopher Watson)
ID Code:	57192
Year Published:	2009
Web of Science® Times Cited:	94
Deposited By:	Geography and Environmental Studies
Deposited On:	2009-06-24
Last Modified:	2013-08-12
Downloads:	12 View Download Statistics