HR: 1330h
AN: G52B-0045    [PDF]
TI: Precise Vertical Station Velocity Estimates in Regional GPS Networks: Monitoring UK Tide Gauge Sites
AU: Teferle, F N
EM: norman.teferle@nottingham.ac.uk
AF: Institute of Engineering Surveying and Space Geodesy, University of Nottingham, University Park, Nottingham, NG7 2RD United Kingdom
AU: * Bingley, R M
EM: richard.bingley@nottingham.ac.uk
AF: Institute of Engineering Surveying and Space Geodesy, University of Nottingham, University Park, Nottingham, NG7 2RD United Kingdom
AU: Dodson, A H
EM: alan.dodson@nottingham.ac.uk
AF: Institute of Engineering Surveying and Space Geodesy, University of Nottingham, University Park, Nottingham, NG7 2RD United Kingdom
AU: Baker, T F
EM: tfb@pol.ac.uk
AF: Proudman Oceanographic Laboratory, Bidston Observatory, Bidston Hill, Prenton, CH43 7RA United Kingdom
AU: Williams, S D
EM: sdwil@pol.ac.uk
AF: Proudman Oceanographic Laboratory, Bidston Observatory, Bidston Hill, Prenton, CH43 7RA United Kingdom
AB: Absolute vertical land/crustal motion rates derived from GPS are required by many geophysical research applications. However, due to the higher noise level in the vertical compared to the horizontal components, quantitative analyses are more difficult and require much longer observation time spans in order to arrive at significant vertical station velocity estimates. Through the analysis of the unfiltered and common mode filtered ITRS2000 coordinate time series of 17 stations in the UK and France, of which 8 are co-located with or close to tide gauge stations, the issues of noise in GPS height time series and the reference frame definition in regional networks are investigated and a strategy for routine analysis is formulated. Using Maximum Likelihood Estimation (MLE) and the empirical methods by {\it Williams} [2003] and {\it Mao et al.} [1999], the stochastic properties of the height time series are described. The MLE is carried out for several noise models identifying a white plus power-law noise model as the best stochastic model closely followed by a white plus flicker noise model. The results for the white plus flicker noise model suggest that it can be used in weekly or monthly analyses, whereas the currently time consuming white plus power-law model is recommended at, e.g. annual or inter-annual intervals. Both empirical methods are compared to the MLE with a white plus flicker noise model and their level of agreement to the MLE is evaluated. The vertical station velocity and uncertainty estimates obtained from these analyses are then compared with vertical land movement estimates from absolute gravimetry and tide gauge measurements, geological information, and to predicted vertical crustal motions computed for several glacial isostatic adjustment models. This comparison reveals an offset in the absolute GPS vertical station velocity estimates which is attributed to the reference frame definition. From this the authors conclude that GPS in the vertical component can currently only be used for relative vertical station velocities and that GPS at tide gauge sites offers the unique opportunity to test for this reference frame bias.
DE: 1200 GEODESY AND GRAVITY
DE: 1229 Reference systems
DE: 1243 Space geodetic surveys
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2003 Fall Meeting