HR: 11:20h
AN: G41C-05    [PDF]
TI: Tidal Aliasing Induced Annual and Semi-annual Artefacts in Continuous GPS Height Time Series
AU: * Penna, N T
EM: nigel.penna@curtin.edu.au
AF: Western Australian Centre for Geodesy, Curtin University, GPO Box U1987, Perth, WA 6845 Australia
AU: Stewart, M P
EM: stewart@vesta.curtin.edu.au
AF: Western Australian Centre for Geodesy, Curtin University, GPO Box U1987, Perth, WA 6845 Australia
AB: Coordinate time series are often derived from continuous GPS data processed as discrete 24 hour solutions. With this approach, residual semi-diurnal and diurnal crustal tide signatures are under-sampled, and aliased periodic signals in the coordinate time series arise. A secondary aliasing effect, well known from satellite altimetry studies but generally ignored in GPS analysis, arises from the repeat period of the satellite orbits being longer than the Nyquist period of the semi-diurnal and diurnal tidal signatures. The theoretical periods for these two aliasing effects are derived for the principal semi-diurnal and diurnal tidal constituents and their presence demonstrated in height time series derived from both simulated and real GPS data. It is shown that the beating of the two aliased signals invariably results in spurious time series signals with semi-annual and annual periods. Hence inadequate modeling of semi-diurnal and diurnal tidal constituents of the site deformation caused by ocean tide loading and Earth tides, can result in spurious semi-annual and annual signatures in the GPS height time series.
DE: 1208 Crustal movements--intraplate (8110)
DE: 1249 Tides--Earth
DE: 1255 Tides--ocean (4560)
SC: Geodesy [G]
MN: 2003 Fall Meeting